Creator Electronics | MAX1301 | Specifications | Creator Electronics MAX1301 Specifications

Industrial
Solutions Guide
Edition 1. May 2010
Industrial: Solutions Guide
A message from the CEO
A message from the CEO
Dear Customers,
Over 27 years ago Maxim was built on the foundation of providing high-quality integrated
circuits for products in the industrial marketplace. In fact, I started designing some of Maxim’s
first data converters in 1984.
Maxim continues to build on its industrial foundation, with more than 25% of its $2 billion
revenue coming today from industrial products. And our mission continues to be to deliver
solutions to our industrial customers that add value to their end products.
The Industrial: Solutions Guide highlights six specific functions and types of industrial equipment. The guide focuses on
the Maxim® products that that will bring you the most value to that specific type of equipment.
We reviewed the 6300 products in our catalog, and selected the best ones for each function or equipment. We listed the
benefits of these products— whether it is smaller size, greater accuracy, lower power, or something else—in an easy-toread format. And we have backed up our claims with hard technical facts so you can compare us to competing solutions.
In addition to identifying our best products and highlighting them in the Industrial: Solutions Guide, we have trained our
direct sales force and worldwide distributors so they understand the technical and marketing needs of your products. In
this way they can provide you high-quality support. They are focused on meeting with you and discussing your needs
and our offerings. I am certain that you will see that Maxim remains focused on being the leading solutions provider for industrial
equipment, both in terms of innovative products and knowledgeable support.
Finally, I welcome your questions and comments about Maxim and this solutions guide. Let me know what you think. You can reach me at: tunc@maxim-ic.com.
Thank you,
Tunç Doluca
President and Chief Executive Officer
www.digikey.com/maxim-industrial
i
Industrial: Solutions Guide
A message from the CEO
ii
Maxim Industrial Solutions
Industrial: Solutions Guide
Table of contents
Table of contents
Programmable logic controllers (PLCs)
Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Analog input function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Analog output functions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Fieldbus functions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Digital I/O functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
CPU functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Isolated power-supply functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Recommended solutions tables. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Sensors
Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
Pressure sensors and weigh scales (force sensing). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
Temperature sensing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
Current, light, and proximity sensing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
Hall-effect sensors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
Sensor communications interface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
Recommended solutions tables. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
Motor control
Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
Monitoring and measuring current for optimal motor control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
Sensing motor speed, position, and movement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
Monitoring and controlling multichannel currents and voltages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
High-accuracy motor control with encoder data interfaces. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
Recommended solutions table. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
Security and surveillance
Digital video recorders (DVRs). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
Recommended solutions table. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
IP cameras. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
Recommended solutions table. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
LED lighting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131
Recommended solutions table. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
Related functions
Trim, calibrate, and adjust. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143
Recommended solutions table. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147
Legal notices. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151
Innovation Delivered is a trademark and Maxim is a registered trademark of Maxim Integrated Products, Inc. © 2010 Maxim Integrated Products, Inc. All rights reserved.
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Industrial: Solutions Guide
Table of contents
iv
Maxim Industrial Solutions
PLCs
Programmable logic controllers (PLCs)
Overview
Overview
new and tougher demands on a PLC:
higher performance, smaller form
factor, and greater functional flexibility. There must be built-in protection
against the potentially damaging
electrostatic discharge (ESD), electromagnetic interference and radio
frequency interference (RFI/EMI),
and high-amplitude transient pulses
found in the harsh industrial setting. Overview
Robust design
Programmable logic controllers
(PLCs) have been an integral part of
factory automation and industrial
process control for decades. PLCs
control a wide array of applications
from simple lighting functions to
environmental systems to chemical
processing plants. These systems
perform many functions, providing
a variety of analog and digital
input and output interfaces; signal
processing; data conversion; and
various communication protocols.
All of the PLC’s components and
functions are centered around the
controller, which is programmed for
a specific task. PLCs are expected to work flawlessly
for years in industrial environments
that are hazardous to the very
microelectronic components that
give modern PLCs their excellent
flexibility and precision. No mixedsignal IC company understands this better than Maxim. Since our
inception, we have led the industry
with exceptional product reliability
and innovative approaches to
protect high-performance electronics
from real environmental dangers,
including high levels of ESD, large
transient voltage swings, and EMI/
RFI. Designers have long endorsed
Maxim’s products because they
solve difficult analog and mixedsignal design problems and
continue solving those problems year after year.
The basic PLC module must be sufficiently flexible and configurable to
meet the diverse needs of different
factories and applications. Input
stimuli (either analog or digital) are
received from machines, sensors,
or process events in the form of
voltage or current. The PLC must
accurately interpret and convert
the stimulus for the CPU which, in
turn, defines a set of instructions
to the output systems that control
actuators on the factory floor or in
another industrial environment. Modern PLCs were introduced in the
1960s, and for decades the general
function and signal-path flow
changed little. However, twenty-firstcentury process control is placing
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Higher integration
PLCs have from four to hundreds of
input/output (I/O) channels in a wide
variety of form factors, so size and
power can be as important as system
accuracy and reliability. Maxim leads
the industry in integrating the right
features into ICs, thereby reducing
the overall system footprint and
power demands and making designs
more compact. Maxim has hundreds
of low-power, high-precision IC’s
in the smallest available footprints,
so the system designer can create
precision products that meet strict
space and power requirements.
Factory automation,
a short history
Assembly lines are a relatively new
invention in human history. There
have likely been many parallel inventions in many countries, but here we
will mention just a few highlights
from the U.S.
Samuel Colt, the U.S. gun manufacturer, demonstrated interchangeable
parts in the mid-1800s. Previously
each gun was assembled with individually made pieces that were filed
to fit. To automate that assembly
process, Mr. Colt placed all the pieces
for ten guns in separate bins and
then assembled a gun by randomly
pulling pieces from the bins. Early in the twentieth century Henry Ford
expanded mass-production techniques. He designed fixed-assembly
stations with cars moving between
positions. Each employee learned
just a few assembly tasks and
performed those tasks for days on
end. In 1954 George Devol applied for U.S. Patent 2,988,237, which
enabled the first industrial robot
named Unimate. By the late 1960s
General Motors® used a PLC to
assemble automobile automatic
transmissions. Dick Morley, known as
the “father” of the PLC, was involved
with the production of the first PLC
for GM®, the Modicon. Morley’s U.S.
Patent 3,761,893 is the basis of many
PLCs today. (For more information on
the above four inventors, please see:
www.wikipedia.org/; for their
patents, search: http://patft.uspto.
gov/netahtml/PTO/srchnum.htm).
Basic PLC operation
How simple can process control be?
Consider a common household space heater.
The heater’s components are
enclosed inside one container, which
3
Programmable logic controllers (PLCs)
Overview
makes system communications easy.
Expanding on this concept is a household forced-air heater with a remote
thermostat. Here the communication
paths are just a few meters and a
voltage control is typically utilized.
FAN
THERMOSTAT
FAN
HEATER
ELEMENT
Think now beyond a small, relatively
simple process-control system.
What controls and configuration are
necessary in a factory?
The resistance of long wires, EMI,
and RFI make voltage-mode control
impractical. Instead, a current loop
is a simple, but elegant solution.
In this design wire resistance is
removed from the equation because
Kirchhoff’s law tells us that the
current anywhere in the loop is
equal to all other points in the loop.
Because the loop impedance and
bandwidth are low (a few hundred
ohms and < 100Hz), EMI and RFI
spurious pickup issues are minimized.
A PLC system is useful for properly
controlling such a factory system.
Current communication
for PLCs
Current-control loops evolved from
early twentieth-century teletype
impact printers, first as 0–60mA
loops and later as 0–20mA loops.
Advances in PLC systems added
4–20mA loops.
A 4–20mA loop has several advantages. Older discrete component
designs required careful design
calculations; circuitry was comparatively large compared to today’s
integrated 4–20mA ICs. Maxim has
introduced several 20mA devices,
including the MAX15500 and
MAX5661, which greatly simplify the
design of a 4–20mA PLC system.
Any measured current-flow level
indicates some information. In
practice, the 4–20mA current loops
operate from a 0mA to 24mA current
range. However, the electrical current
ranges from 0mA to 4mA and 20mA
to 24mA are used for diagnostics
4
RELAY
ROOM
THERMOSTAT
AC
PLUG
A household electric heater serves as a simple example of process control.
ONE KILOMETER OF WIRE
CONTROL ROOM
INDUSTRIAL-SIZED HEATER
Longer-range factory communications.
and system calibration. Since current
levels below 4mA and above 20mA
are used for diagnostics, one might
conclude that readings between
0mA and 4mA could indicate a
broken wire in the system. Similarly,
a current level between 20mA and
24mA could indicate a potential
short circuit in the system.
compatible with 4–20mA instrumentation. A HART system allows
two-way communications with
smart, microprocessor-based, intelligent field devices. The HART protocol
allows additional digital information
to be carried on the same pair of wires
with the 4–20mA analog current signal
for process-control applications.
An enhancement for 4–20mA
communications is the highwayaddressable remote transducer
(HART™ system) which is backward
PLCs can be described by separating
them into several functional groups.
Many PLC manufacturers will organize
these functions into individual
ISOLATED POWER-SUPPLY FUNCTIONS
ANALOG
INPUT
ANALOG
OUTPUT
CONTROLLER/
SECURE
MICROCONTROLLER
SENSORS
DIGITAL I/O
DIGITAL I/O
OTHER
PLC
UNITS
ACTUATORS
FIELDBUS
OTHER
PLC
UNITS
= MAXIM SOLUTION
Simplified PLC block diagram. For a list of Maxim's recommended PLC solutions, please go to: www.maxim-ic.com/plc.
Maxim Industrial Solutions
Programmable logic controllers (PLCs)
Overview
modules; the exact content of each
of these modules will likely be as
diverse as are the applications. Many
modules have multiple functions that
can interface with multiple sensor
interfaces. Yet other modules or
expansion modules are often
dedicated to a specific application
such as a resistance temperature
detector (RTD), sensor, or thermocouple sensor. In general, all modules
have the same core functions: analog
input, analog output, distributed
control (e.g., a fieldbus), interface,
digital input and outputs (I/Os), CPU,
and power. We will examine each of
these core functions in turn, and
leave sensors and sensor interfaces
for a separate section.
www.maxim-ic.com/plc
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5
Programmable logic controllers (PLCs)
Analog input function
Analog input function
Overview
The analog input portion of a PLC
accepts analog signals from a variety
of sensors and factory or field wiring.
These sensors are used to convert
physical phenomena such as light,
temperature, sound, gas, or vibration
from mechanical signals into
electrical representations. In the analog-input signal path, signals are
conditioned for maximum integrity,
range, and resolution before being
sampled by the analog-to-digital
converters (ADCs). In the industrial
environment common to PLCs, there is a wide variety of signal levels,
signal bandwidths, and noise
sources. It is, therefore, essential to
reject as much of the irrelevant information as possible. Equally
important, the maximum amount of relevant information must be
retained when the signals are
converted from the analog to the
digital domain.
The PLC’s analog input accepts
voltage and current inputs from
remote sensors. Voltage inputs can
have different amplitudes, the most
common of which are either 0 to
10V, or 0 to 5V, ±10V, or ±5V. The
most popular current-input standard
is 4–20mA, although ±20mA is
sometimes used. Despite its name,
the 4–20mA standard accepts
0–24mA both to detect an open
input (< 3.6mA) and overrange (> 20mA), and to allow headroom
for calibration. To guarantee that
the current loop is never broken, the
current input is typically terminated
into a relatively low-value resistor
(e.g., 50Ω to 250Ω) prior to the signalconditioning analog chain.
followed by a common amplifying
signal path into an ADC, or with
individual amplifying channels and
a multiplexer prior to the ADC. The
input stage is commonly required
to cope with both positive and
negative high voltages (e.g., ±30V
or higher). This protects the PLC’s
analog-input card from external fault
conditions and lets the input module
accommodate variable commonmode voltages on the long lines
that connect to the remote sensors.
Low-temperature drift and low noise
are also critical requirements of the
analog signal path. The errors at
+25°C are typically calibrated out in
software. The drift over temperature
can also be removed, although it is
not removed in many systems and
thus becomes a critical specification.
The signal chain
Various implementations of the
signal chain are possible, with
simultaneous-sampling ADCs and
independent conditioning amplifiers,
or with a multiplexer as the first stage
BUFFER
AC VOLTAGE/CURRENT
TRANSFORMERS (TIMES 6)
Analog-to-digital conversion
Standard PLC designs typically
require a high-accuracy ADC. The
bandwidth of the input signal
SIMULTANEOUS
SAMPLING*
ADC
OP AMP OR
INSTRUMENTATION AMP
FROM ANALOG
SENSORS AND
FIELD WIRING
ISOLATION
MUX
TO CPU
MODULE
ADC
ACTIVE FILTERS
ANALOG FRONT-END (AFE) FILTERS & RESISTORS
ESD/SIGNAL
PROTECTION
RFI/EMI
FILTERS
SENSOR SIGNAL
CONDITIONER
PRECISION
RESISTORS
= MAXIM SOLUTION
VOLTAGE
REFERENCE
SWITCHED
C FILTERS
DIGITAL
POTENTIOMETER
THERMAL
MANAGEMENT
VOLTAGE
MONITORS
ISOLATED POWER SUPPLY
*Designers can choose among multiple ADCs for this function.
Maxim’s extensive product offerings are found throughout this block diagram of PLC analog-input functions.
For a list of Maxim's recommended PLC solutions, please go to: www.maxim-ic.com/plc.
6
Maxim Industrial Solutions
Programmable logic controllers (PLCs)
Analog input function
dictates the ADC’s maximum
sampling rate. The signal-to-noise
ratio (SNR) and spurious-free
dynamic range (SFDR) specifications
dictate the ADC’s resolution, filtering
requirements, and gain stages. It is
also important to determine how
the ADC will interface to the microcontroller or CPU. For example,
high-bandwidth applications
perform better using a parallel or
fast serial interface. With its two-line
digital interface, however, I2C is ideal
for slower systems. When the results
from the analog-input measurement
are transferred through a 4–20mA
loop, PLC designers can choose
between an ADC with a separate
digital-to-analog converter (DAC),
an integrated DAC that can drive the 4–20mA lines directly, or a highvoltage op amp configured as a
precision current source. Applications
that require extraction of phase
information between channels are
well suited for multiple ADCs or
simultaneous-sampling ADCs.
Although PLCs are used in distinct
ways, many PLC designs share some
common factors. For example, the
most used ADCs and DACs are 16
bits. Maxim offers over a hundred
16-bit ADCs and DACs for a wide
range of input and output voltages,
and this broad product offering
is a distinct advantage for the
PLC designer. Consider a situation
where using sensors with varying
accuracies could dictate the need
for three ADCs with 12-, 14-, and
16-bit resolution. But to reduce cost
and complexity, it may be best to
discard bits for some sensors and
utilize the higher resolution only
where it is needed. In this case, a
designer may choose to multiplex
the analog signals to a differential
input amplifier or programmable
gain amplifier (PGA) into a single
16-bit ADC.
When choosing a multiplexer, sensor
reaction speed must be considered.
This means that a designer needs
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provide ±16V transient protection to
prevent damage to the PLC system. to determine the input bandwidth
and how quickly the switches will be
opening and closing. Slow-response
sensors measuring signals such as
temperature and humidity can be
sensed every few seconds. Faster
changes like speed, position, and
torque typically need to be sensed at
least thousands of times per second.
Similarly, on the output side DACs
can be multiplexed depending on
how often the outputs must be
serviced to maintain control.
Signal conditioning and
calibration
There are many design challenges
when selecting the analog-input
signal-path components. The inputs
to the multiplexer and the ADC
require analog signal conditioning
such as filtering; converting currents
to voltages; and changing gain, offset,
impedance, and bias. Caution must be
taken both to anticipate the expected
voltage amplitude and signal polarity,
and to understand the unexpected
like unwanted voltage or current
transients. Maxim provides a wide
selection of operational amplifiers,
instrumentation amps, PGAs, precision
resistors, filters, references, ADCs, and
multiplexers to aid the PLC design.
Calibration improves system performance and increases accuracy
(see chapter titled "Trim, calibrate,
and adjust" on page 143. The MAX9939,
a PGA with an SPI™ interface, is
ideally suited for a thermocouple
application as it provides the needed
level-shifting circuitry to signal
condition both negative and positive
sensor signals. The MAX9939’s inputs
Multiplexers (muxes) are useful for
switching multiple input channels. A
mux that meets high-voltage-supply
requirements (up to ±35kV) or is
fault protected against overvoltage
conditions, can help eliminate
expensive external circuitry such as
voltage-dividers and opto relays. A low, matching on-resistance (RON) is essential for low distortion
to improve circuit reliability, and low-leakage currents are critical for
minimizing voltage-measurement
errors. Maxim‘s product portfolio
includes more than 15 faultprotected/high-voltage, low-
leakage, and low-RON muxes
ideal for PLC applications. The designer will choose the physical
position for the signal-conditioning
circuits. That placement may require
the sensor signal to be conditioned
before it is transmitted to the input ADC. The sensor’s output can be very small
or very large, which would require gain
or attenuation stages (respectively) to
maximize the ADC’s dynamic input
range. These conditioning stages are
usually implemented with PGAs or
discrete op amps and precision resistor-dividers. The ADC and
amplifier work in tandem to achieve
the best signal-to-noise ratio (SNR)
within the cost, power, and size
budgets. Another alternative is to use
an ADC with the conditioning stages
integrated. Regardless of how the signal-
conditioning stages are implemented,
the voltage range, low-temperature
drift, and low noise are among the
most critical specifications when
determining the best architecture.
The industrial environment presents
numerous noise sources, such as
50HZ/60Hz power-line mains which
get coupled into the signal. These
unwanted noise signals put an artificial limit on the gain stages and
7
Programmable logic controllers (PLCs)
Analog input function
should be rejected before the gain
stages. This is best accomplished
using Maxim’s PGAs or differential
amplifiers with a high commonmode rejection ratio (CMRR). Maxim
has a variety of laser-trimmed,
matching resistor-dividers for precise
gain and attenuation; there are also
trimmable calibration potentiometers
8
for programmability, and ADCs with
differential inputs and PGAs integrated in a single IC.
Lowpass or bandpass filtering
before the ADC sampling network is
necessary for anti-aliasing requirements and for rejecting noise sources
at other frequencies. PLC designers
have a choice between active filters
implemented with op amps or
switched-capacitor filters with a
very sharp (up to 8-pole) rolloff and
a programmable cut-off frequency.
Maxim provides a selection of 5thand 8th-order, switched-capacitor
and continuous-time filters ideal for
anti-aliasing.
Maxim Industrial Solutions
Programmable logic controllers (PLCs)
Analog input function
Eliminate external overvoltage protection (OVP) circuitry and reduce BOM complexity
with high-voltage multiplexers
MAX14752/MAX14753
Benefits
The MAX14752/MAX14753 are 8-to-1 and dual 4-to-1 (respectively)
high-voltage analog multiplexers designed for high-voltage PLC
applications. Both devices operate with dual supplies of ±10V to ±36V
or a single supply of 20V to 72V, and a low 0.03Ω (typ) RON flatness.
Logic levels for the channel-select interface are defined by the device
enable (EN) input to help interface with multivoltage systems. The
MAX14752/MAX14753 are packaged in the standard 16-pin TSSOP,
and are pin compatible with the industry-standard DG408/DG409.
Both multiplexers are specified over the extended -40°C to +85°C
operating temperature range.
•• High supply voltage eliminates external
OVP diodes and opto relays
–– Wide, single 72V (max) power-supply
range; dual ±36V (max) power-supply
range
–– Internal protection diodes can be used
for OVP
–– Rain-to-rail operation gives large
dynamic range
•• Excellent RON flatness for highaccuracy measurements
–– 0.03Ω (typ) RON flatness over
common-mode voltage
•• Flexible logic levels for interfacing with
multivoltage systems
–– Device enable (EN) defines voltage logic
level of channel-select inputs
•• Easy upgrade path
–– Pin compatible with industry-standard
MAX308/MAX309/DG408/DG409
VDD
MAX14752
RLIM
RLIM
RLIM
RLIM
OUT
RLIM
RLIM
RLIM
RLIM
CONTROL
VSS
S0
S1
S2 EN GND
Input overvoltage and undervoltage clamping with the MAX14752.
www.digikey.com/maxim-industrial
9
Programmable logic controllers (PLCs)
Analog input function
Improve accuracy with precision over time and precision over temperature from
ultra-high-precision op amps
MAX4238/MAX4239
Benefits
The MAX4238/MAX4239 are low-noise, low-drift, ultra-high-precision
amplifiers. They offer near-zero DC offset and drift by using patented
autocorrelating zeroing techniques.* This method constantly
measures and compensates the input offset, thereby eliminating
drift over time and temperature and the effect of 1/f noise.
•• Maintain system calibration and
accuracy over time and temperature
with low-temperature coefficients
–– Autozero technology reduces voltage
offset temperature coefficient (TCVOS)
to 10nV/°C and VOS to only 2.5µV( max)
•• Improve system accuracy and
resolution with low-input voltage noise
–– No 1/f component ensures low-distortion
signal conditioning below 0.1Hz with
30nV input-voltage noise density
5V
18kΩ
360Ω
STRAIN GAUGE
AV = 100
18kΩ
AIN
ADC
MAX4238
MAX4239
The MAX4238/MAX4239 op amps are ideal for driving ADCs.
*U.S. Patent #6,734,723.
10
Maxim Industrial Solutions
Programmable logic controllers (PLCs)
Analog input function
Reduce component count with precision differential PGA that supports positive and
negative sensor signals
MAX9939
Benefits
The MAX9939 is a precision, differential-input PGA ideal for conditioning wide-dynamic-range signals like those found in automotive
current sense, medical instrumentation, and industrial dataacquisition applications. The MAX9939 features SPI-programmable
differential gains from 0.2V/V to 157V/V, input VOS compensation, and an
output amplifier that can be configured either as a high-order active
filter or to provide a differential output.
•• No extra components needed for a wide
range of sensor-input voltages
–– 0.2V/V to 157V/V SPI-programmable
gains
•• Enhanced SNR performance reduces
effects of unwanted signal noise
–– Differential-input and differential-output
configuration improves the signal-
conditioning resolution and accuracy •• Improved signal-path robustness
–– Inputs can withstand ±16V transients
Input common-mode voltage
extends 1V below ground
even at high gain—ideal for
power-ground voltage spikes
Internal matched
resistors for high
CMRR and low-gain
tempco
RELAY
5MHz SPI bus to set
gain from 0.2 to 156!
M
SPI
–
+
VCC/2
Input switches for
on-command VOS
calibration by
firmware
µC
+
–
VCC/2
MAX9939
Internal VREF = VCC/2
allows bidirectional
current sense
ADC
Integrated output op amp
for active filter applications
or differential outputs
The MAX9939 uses matched resistors to provide a wide range of gains.
www.digikey.com/maxim-industrial
11
Programmable logic controllers (PLCs)
Analog input function
16-bit ADC with software-programmable input ranges on each ADC channel saves
design time
MAX1300*/MAX1301/MAX1302*/MAX1303
Benefits
The MAX1300–MAX1303 ADC family is an ideal fit for PLC applications because they measure many unique unipolar and bipolar input
ranges, all with 16-bit operation and no missing codes. The eight
single-ended or differential input ranges vary from as low as a unipolar
0 to 2.048V full scale up to a bipolar ±12.288V full scale. Each input
channel can be programmed by software for a different input range,
making the MAX1300 family highly versatile. By eliminating analog
front-end (AFE) stages, these ADCs also reduce cost and area, while
increasing accuracy. The ADCs are also available with 14-bit resolution and 4 or 8 channels.
•• Reduce complexity and cost by
eliminating external gain stages and
muxes
–– Each ADC measures eight unique bipolar
and unipolar input ranges
–– Multiple software-programmable input
ranges up to ±12.288V full scale
•• Flexible, easy-to-reuse circuit for
multiple applications
–– 16-bit and 14-bit resolution in the same
package
•• Eliminate external protection
components and save space and cost
–– Up to ±16.5V analog-input protection +12V
DC-DC
DVDD
AVDD
MAX1300*/MAX1031
MAX1302*/MAX1303
LOGIC
-12V
SCLK
SPI
DOUT
16.5V FAULT
TOLERANT
MUX
PGA
16-/14-BIT
SAR ADC
FIFO
REFADJ
REF
PLC
System
+VREF
REF
DGND
-VREF
AGND
CS
ISOLATED ANALOG-INPUT BOARD
ISOLATION
BARRIER
The MAX1300–MAX1303 ADCs reduce cost by offering programmable input-voltage ranges.
* Future product—contact factory for availability.
12
Maxim Industrial Solutions
Programmable logic controllers (PLCs)
Analog input function
ADC eases firmware complexity by capturing accurate phase and magnitude
information on up to 32 channels
MAX11040
Benefits
The MAX11040 sigma-delta ADC offers 117dB SNR, four differential
channels, and simultaneous sampling that is expandable to 32
channels (eight MAX11040 ADCs in parallel). With programmable
phase and sampling rate, the MAX11040 is ideal for high-precision,
phase-critical measurements within a noisy PLC environment. With a single command, the MAX11040’s SPI-compatible serial interface
allows data to be read from all the cascaded devices. Four modulators
simultaneously convert each fully differential analog input with a 0.25ksps to 64ksps programmable data-output-rate range. The
device achieves 106dB SNR at 16ksps and 117dB SNR at 1ksps.
•• Simplifies digital interface to a
microcontroller
–– Eight MAX11040 ADCs can be daisychained through the SPI interface
•• Easily measures a wide dynamic range
–– 106dB SNR allows users to measure both
very small and large input voltages
•• Easily measures the phase relationship
between multiple input channels
–– Simultaneous sampling preserves phase
integrity on multiple channels
S
PI C
eS
ngl
Si
µC
4-channel,
fully differential
bipolar inputs
AIN0+
AIN0REF0
AIN1+
AIN1REF1
AIN2+
AIN2REF2
AIN3+
AIN3REF3
AVDD
DVDD
ADC
DIGITAL FILTER
ADC
DIGITAL FILTER
ADC
DIGITAL FILTER
ADC
DIGITAL FILTER
MAX11040
2.5V
REF
XTAL
OSCILLATOR
SPI/DSP
SERIAL
INTERFACE
SYNC
CASCIN
CASCOUT
SPI/DSP
CS
SCLK
DIN
DOUT
INT
N=8
SAMPLING
PHASE/FREQ
ADJUSTMENT
N=1
N=2
Fine/coarse samplerate and phase adjustment
XIN XOUT
AGND
DGND
The MAX11040 can be cascaded up to 32 channels.
www.digikey.com/maxim-industrial
13
Programmable logic controllers (PLCs)
Analog output functions
Analog output functions
Overview
understand the necessity of controlling full-scale gain variations and
the multiple reset levels for bipolar
and unipolar voltages and different
output-current levels.
The analog output remotely controls
activities and functions. It can be
part of a complex loop like a PLC or a
proportional-integral-derivative (PID)
system, or it can perform a simple
function such as turning a light or fan
on and off. Signal protection
The analog output circuitry is
connected to wiring, long and short
in the field or factory, so the output
module must protect the system
from ESD, RFI, and EMI. Voltage
outputs tend to be appropriate for
short-distance transmission wiring;
current outputs are commonly used on
long cables to reduce EMI from sources
like arcing switches and motors. The analog output primarily takes
commands from the microprocessor
and translates them into analog and
digital signals to control motors,
valves, and relays. As an example, a digital word from the CPU can be
converted to an analog voltage or
current by a DAC and signal-
conditioning circuitry. A proper
signal is tailored for each output with
any needed signal conditioning
provided, including bias, offset, and
gain calibration. Calibration issues are discussed in the chapter entitled
"Trim, calibrate, and adjust" on page 143.
Producing discrete, selectable,
voltage- (bipolar and unipolar) or
current-output conditioning circuits
can be an intimidating task. This
is especially true as one begins to
Signal monitoring
careful monitoring. As a cable is
failing, there is usually a period
of intermittent operation prior to
complete failure. The intermittent
operation offers an opportunity to
detect the error before complete
failure occurs. As an important part of
preventive maintenance, this failure
detection improves safety and helps
to minimize any plant downtime.
Output signal-monitoring functions,
including detection and reporting
of intermittent wire faults, are
important safety considerations.
Cabling in the field or factories is
subject to movement and vibration
which, in time, will cause wires to
open or short to other conductors.
Equipment and personnel must
remain safe, which necessitates
Because EMI, RFI, and power-surge
conditions can be extreme in a
factory, any monitoring must be
reliable and not subject to nuisance
tripping. Error reporting must
be robust. In practice, reporting
is done by establishing minimum
timeout periods for detecting and
reporting errors. A large noise
pulse, for example, can appear like a
CONDITIONING CIRCUITRY
DEMUX
PRECISION
RESISTORS
RFI/EMI
FILTERS
SWITCHED
C FILTERS
SENSOR SIGNAL
CONDITIONER
ESD/SIGNAL
PROTECTION
DIGITAL
POTENTIOMETER
HART
MODEM
ANALOG OUTPUT:
V TO V, OR I TO V
FROM CPU
MODULE
DAC
ISOLATION
VOLTAGE/
CURRENT
TO FIELD
WIRING AND
ANALOG
ACTUATORS
DAC
EXCITEMENT, BIAS,
CALIBRATION TO
FIELD WIRING AND
INPUT SENSORS
VOLTAGE
REFERENCE
VOLTAGE
MONITORS
TO ALL
HOT-SWAP
CONTROLLER
THERMAL
MANAGEMENT
ISOLATED POWER SUPPLY
= MAXIM SOLUTION
Maxim’s product offerings are found throughout this block diagram of PLC analog-output functions.
For a list of Maxim's recommended PLC solutions, please go to: www.maxim-ic.com/plc.
14
Maxim Industrial Solutions
Programmable logic controllers (PLCs)
Analog output functions
momentary cable interruption, but
that is not necessarily the case. The
mechanical cable interruption will
tend to last longer than the noise
pulse. The noise pulse is typically
caused by capacitive or inductive
coupling of a large change in current
in a second cable running close to
the communications cable. This
noise interruption can occur when
a large motor is turned on or off,
and the transition (rise or fall time)
of the change in current is seen as a
differentiated pulse of short duration
on the communications cable.
Consequently, waiting for a short
time (a fraction of a second) allows the
fault detector to distinguish between
a real cable intermittent fault and a
noise pulse. The detection period
must be long enough to avoid false
error reports caused by fast transients
that are part of the harsh environment, and yet short enough to catch
short mechanical cable errors.
www.digikey.com/maxim-industrial
Extra safety is provided if more
conditions than just cable health are
monitored. Chip temperature, and
thus the environment over temperature, is one important example. The
field or factory can be spread over
several acres, so monitoring powersupply voltage drops or brownout is
also important for system reliability.
common wiring errors and shorts.
Some faults cannot be tolerated,
such as a direct lightning hit.
However, the outputs should withstand reasonable fault voltages. The
most common errors are shorts to
ground or the 24V power supply, and
these errors should be tolerated with-
out the need to replace components.
Managing an output fault
Managing system functions
If an output fault occurs, errors
must be latched and presented to a
hardware interrupt pin. This gives the
system microprocessor time to react
to short cable outages. By definition,
intermittent cable faults will be asynchronous and many will occur while
the processor is busy. The interrupt is
generated so the processor can then
poll the output device registers for the
exact condition and clear the interrupt.
Some sensors require excitation
to function, and the output module
supplies such signals. Typical examples
are an AC signal for capacitive and
variable reluctance sensors or a DC
signal for a simple LED in a backlighted switch.
The output to the field or factory
needs to be protected against
The analog output can also provide
other system-management functions
that include monitoring the local
isolated power supply, board
temperature, and calibration.
15
Programmable logic controllers (PLCs)
Analog output functions
Eliminate 31 DACs and reduce system cost with a 32-output sample/hold amplifier
MAX5167
Benefits
The MAX5167 contains 32 buffered sample/hold amplifier circuits
with internal hold capacitors. The internal hold capacitors minimize
leakage current, dielectric absorption, feedthrough, and required
board space. The hold capacitors also provide fast 2.5μs (typ) acquisition time while maintaining a relatively low 1mV/s (typ) droop
rate. This performance makes the MAX5167 sample/hold amplifier
ideal for high-speed sampling.
•• Highly integrated and easy to design in
–– 32-channel sample/hold
–– Output clamps on each channel
–– Wide +7V to -4V output voltage range
–– Cascade two MAX5167s to form 64
output channels
•• Unparalleled accuracy and linearity
meet system error budget
–– 0.01% accuracy of acquired signal
–– 0.01% linearity error
–– Fast 2.5µs acquisition time
–– Low 1mV/s droop rate
–– Low 0.25mV hold step
The MAX5167 has five address lines as inputs to a demultiplexer
which selects one of the 32 outputs. The analog input is connected
to the addressed sample/hold amplifiers when directed by the
control logic.
VL
SELECT
ADDRESS BUS
ADDR0-ADDR4
ADDRESS LOGIC
CS
MAX5167
SWITCHES 0-31
S/H
OUT0
OUT1
DATA BUS
DAC
IN
OUT30
OUT31
CONFIG
Block diagram of the MAX5167.
16
Maxim Industrial Solutions
Programmable logic controllers (PLCs)
Analog output functions
System flexibility and reduced cost with multichannel DACs
MAX5134/MAX5135/MAX5136/MAX5137
Benefits
The MAX5134–MAX5137 are pin- and software-compatible, 16-bit
and 12-bit DACs offering low power, buffered voltage output, and
high linearity. They use a precision internal reference or a precision
external reference for rail-to-rail operation. The MAX5134–MAX5137
accept a wide 2.7V to 5.25V supply-voltage range to accommodate
most low-power and low-voltage applications.
•• Flexible upgrade path
–– 2-/4-channel, 16-/12-bit DACs are pin
and software compatible
•• Save cost and board space
–– Parts accept an SPI/QSPI™-/
MICROWIRE™-/DSP-compatible serial interface
–– 4mm x 4mm package
–– A READY output enables easy daisychaining of several MAX5134–MAX5137
and other compatible devices
–– Double-buffered hardware and software
LDAC provides simultaneous output
updates
•• Improve safety
–– Hardware input for resetting the
DAC outputs to zero or midscale on
power-up or reset
DVDD
AVDD
M/Z
Selectable pin to power
up to zero or midscale
MAX5134/MAX5136
MAX5135/MAX5137
16-/12-BIT
OUT_4
16-/12-BIT
OUT_3
16-/12-BIT
OUT_2
16-/12-BIT
OUT_1
CS
SCLK
DIN
SPI
INTERFACE
RDY
RDY pin to facilitate
daisy-chaining
LDAC
Asynchronous LDAC pin
to simultaneously
update all outputs
DOUBLEBUFFERED
REGISTERS
INTERNAL
REFERENCE
IN
OUT
Integrated precision
reference (10ppm/°C)
Block diagram of the MAX5134–MAX5137 DACs.
www.digikey.com/maxim-industrial
17
Programmable logic controllers (PLCs)
Analog output functions
Enhance system safety and reliability with an output conditioner
MAX15500/MAX15501
Benefits
The MAX15500/MAX15501 analog output conditioners provide a
programmable current up to ±24mA, or a voltage up to ±12V proportional to a control voltage signal. The control voltage is typically
supplied by an external DAC with an output voltage range of 0 to
4.096V (MAX15500) and 0 to 2.5V (MAX15501). The output current and
voltage are selectable as either unipolar or bipolar. The MAX15500/
MAX15501 are programmed through an SPI interface capable of
daisy-chained operation.
•• Enhance reliability
–– Outputs are protected against overcurrent conditions
–– Outputs are protected against a short to
ground or supply voltages up to ±35V
DVDD
AVDD
SAFETY MONITORING
AVDDO
MAX15500
MAX15501
SCLK
Save one
digital isolator
per channel
with new easy
daisy-chain
DIN
DOUT
CS1
SPI
INTERFACE
CS2
READY
BIDIRECTIONAL
CURRENT
DRIVER
MON
REFIN
ERROR
HANDLING
FSMODE
FSSEL
AVSSO
SENSERN
COMP
OVERCURRENT
PROTECTION
BIDIRECTIONAL
CURRENT
DRIVER
AVSS
Special
intermittent
cable conditions
SENSERP
ERROR
HANDLING
AIN
ERROR
•• Ease equipment installation and
improve diagnostics
–– Output current and voltage are
selectable as unipolar or bipolar
–– Monitor for overtemperature and supply brownout conditions with programmable threshold
–– Extensive error reporting through
the SPI interface and an additional
open-drain interrupt output
–– Analog output to monitor load
conditions
Current-mode
open
Voltage-mode
short
OUT
Internal
overtemperature
SENSEVP
Supply brownout
w/adj threshold
SENSEVN
AGND
DGND
OUTDIS
Output mirror enables
external dynamic
load monitoring
Block diagram of the MAX15500/MAX15501.
18
Maxim Industrial Solutions
Programmable logic controllers (PLCs)
Analog output functions
16-bit DAC with integrated voltage-and current-output conditioner reduces board
area and eliminates external components
MAX5661
Benefits
The MAX5661 DAC controls output voltage, output current, and output
gain adjustments. This device reduces the challenges that designers
face when laying out their analog and mixed-signal boards. •• Simplifies board design
–– Software-selectable voltage output or
current output
•• Eliminates external components
–– Integrated output buffer
–– No additional discrete components
required for switching between output
modes
•• Improves system reliability
–– Supports analog power supplies up to 37.5V
LDAC
SOFTWARE
LOAD DAC
CONTROL
REGISTER
CS
SCLK
FULL-SCALE
OUTPUT ADJUST
FULL-SCALE
ADJUST
REGISTER
SHIFT
REGISTER
INPUT
REGISTER
DIN
DAC
REGISTER
DAC
2-TO-1
MUX
DOUT
TO OUTPUT
CIRCUITRY
OUTI
OUTV
CLEAR
REGISTER
MAX5661
A simplified block diagram of the MAX5661.
www.digikey.com/maxim-industrial
19
Programmable logic controllers (PLCs)
Analog output functions
Improve system accuracy for high-voltage applications in a harsh environment with
high-precision output conditioners and drivers
MAX9943/MAX9944
Benefits
The MAX9943/MAX9944 are high-voltage amplifiers (6V to 38V) that
offer precision (100µVOS), low drift (0.4µV/°C), and low 550µA power
consumption. The devices are ideal for sensor signal conditioning,
high-performance industrial instrumentation, and loop-powered
systems (e.g., 4mA–20mA transmitters).
•• Easily drive 24V 4–20mA lines
throughout factory floors
–– High supply-voltage operation and
high-output drive exceed current-mode
communication requirements
Wide 6V to
38V supply
voltage
+18V
1/2
MAX9944
VREF
Low 100μV (max)
input voltage offset VOS
High 25mA output
current to drive
4–20mA loop-powered
systems
1/2
MAX9944
RSENSE
Low 550μA quiescent
current helps reduce
static system power
dissipation
RLOAD
-18V
Stable with up to
1nF capacitive load
The MAX9944 accurately drives loads.
20
Maxim Industrial Solutions
Programmable logic controllers (PLCs)
Analog output functions
Resistor network saves cost and space without sacrificing system precision
MAX5490/MAX5491/MAX5492
Benefits
The MAX5490 family of precision resistor-dividers consists of two
accurately matched resistors with access to the ends and center
of the divider. This family offers excellent resistance matching of
0.035% (A grade), 0.05% (B grade), and 0.1% (C grade). It includes an
extremely low resistance-ratio temperature drift of 2ppm/°C over
-40°C to +85°C, and has an end-to-end resistance of 30kΩ. Resistance
ratios from 1:1 to 30:1 are available, as are ten standard ratios.
•• Inexpensive and easy to use
–– Up to 80V operating voltage across sum
of R1 and R2
–– Resistance ratios from 1:1 to 30:1
–– Tight initial ratio accuracy
–– Three grades: 0.035%, 0.05%, and 0.1%
–– Low 2ppm/°C resistor-ratio drift
•• Saves board space
–– Tiny 3-pin SOT23 package
MAX5491
−
DAC
+
MAX4238
Implementing a robust, precision analog output with the MAX5491.
www.digikey.com/maxim-industrial
21
Programmable logic controllers (PLCs)
Analog output functions
Save space in low-power process-control equipment with a single-chip HART modem
DS8500
Benefits
The DS8500 is a single-chip modem with HART capabilities that
satisfy the HART physical-layer requirements. This device operates
in half-duplex fashion, and integrates the modulation and demodulation of the 1200Hz/2200Hz FSK signal while consuming very low
power. It only needs a few external components because of the integrated digital-signal processing.
•• Higher density due to low-power draw
–– 285μA (max) current consumption
•• Saves space
–– Fewest external components due to the
built-in digital-receive filter
–– 20-pin, 5mm x 5mm x 0.8mm TQFN
package
•• Easily available crystal
–– Uses a standard 3.6864MHz clock input
•• Robust signaling due to lowest
harmonic distortion
–– Sinusoidal output signal
XTAL1
XTAL2
CRYSTAL
OSCILLATOR
RST
DVDD DGND
CLOCK
GENERATOR
POWER
MONITOR
AGND
AVDD
VREF
1.23V
REF
XCEN
OCD
D_OUT
RTS
D_IN
Rx
DEMODULATOR
DIGITAL
FILTER
Tx
MODULATOR
SAMPLE/HOLD
ADC
DAC
FSK_IN
FSK_OUT
DS8500
Block diagram of the DS8500.
22
Maxim Industrial Solutions
Programmable logic controllers (PLCs)
Fieldbus functions
Fieldbus functions
Overview
A fieldbus is the communication
medium used in industrial automation systems and in process control
to interconnect subsystems that are spatially dispersed. Distributed
control allows local, hierarchical
control. There is an important
advantage of such a noncentralized
control strategy: it avoids high
processing power and extensive
cabling. Control subsystems can be
located close to the sensors and
actuators in the field. An example of a fieldbus network is an automobile
assembly line, where the fieldbus
interconnects controllers located at
each assembly stage.
Basic composition of a
fieldbus
primarily used to network multiple
controllers in decentralized locations.
A PLC system has a hierarchical
structure in which the upper levels of the fieldbus network use Ethernetbased networking. This hierarchy
melds with the other corporatemanagement IT systems.
The physical layer of a fieldbus is
commonly based on RS-485, CAN,
and Ethernet. The fieldbus connects
to a PLC subsystem with a fieldbus
module, as shown below.
Fieldbuses are bidirectional, digital,
serial networks. CANopen, CCLINK,
ControlNet, DeviceNet, Ethernet,
Interbus, Modbus®, and PROFIBUS
are examples of fieldbus networks.
PROFIBUS DP (decentralized peripheral) has become one of the most
commonly used fieldbuses for
factory automation. PROFIBUS DP is
The fieldbus module bridges the
PLC’s system backplane to the
fieldbus. The backplane, which is
common to all modules in the PLC
system, can be based on half- or
full-duplex RS-485. RS-485 is ideally
suited to backplane interconnect in
industrial applications because of its
high-EMI tolerance, high speed, and
hot-plug capability.
FIELDBUS OR SENSOR/ACTUATOR BUS
COMMUNICATION
INDUSTRIAL ETHERNET
The fieldbus supports communications throughout the factory.
www.digikey.com/maxim-industrial
23
Programmable logic controllers (PLCs)
Fieldbus functions
In the fieldbus module the controller converts the backplane protocol
to the fieldbus protocol. Universal
asynchronous receiver-transmitters
(UARTs) define the fieldbus data
rates, ensure data integrity, and
interface to either the RS-485 or
PROFIBUS transceivers.
Harsh conditions typical of industrial
applications can make protecting
the interface cabling and devices
a challenge. It is crucial, therefore,
that both the device(s) and system
withstand harsh conditions. Only in
this way can one ensure that the PLC
system’s signal integrity and system
reliability are maintained.
• Fault protection: tolerance to
shorts up to ±80V
To ensure that the system is protected in harsh industrial environments,
PLC designers need to incorporate
quite specific safeguards: • Line termination to reduce reflections on the cables
• Isolation to allow large commonmode ground differentials
• Automotive temperature grade
(-40°C to +125°C)
• Protection from high ESD: up to
±35kV (HBM) and ±20kV (Air Gap,
IEC 61000-4-2) BACKPLANE
HOT-SWAP
CONTROLLER
VOLTAGE
MONITORS
FIELDBUS
ISOLATED POWER SUPPLY
ETHERNET
TERMINATION
RS-485
CONTROLLER
UART
RS-485
ISOLATION
LVDS
CAN
FAULT
PROTECTION
RS-232
PROFIBUS
= MAXIM SOLUTION
The fieldbus is connected to the PLC backplane by the fieldbus module. For a list of Maxim's recommended PLC solutions, please go to: www.maxim-ic.com/plc.
24
Maxim Industrial Solutions
Programmable logic controllers (PLCs)
Fieldbus functions
Transceiver meets PROFIBUS DP standards and protects
against ±35kV ESD
MAX14770E
Benefits
The MAX14770E PROFIBUS DP transceiver meets strict PROFIBUS
standards with a high-output-drive differential (greater than 2.1V)
and an 8pF bus capacitance. The high-ESD protection (±35kV, HBM),
high-automotive-temperature grade, and space-saving 8-pin TQFN
package make the MAX14770E ideal for space-constrained, harsh
industrial environments. •• Easy to connect to PROFIBUS networks
–– Meets EIA 61158-2 Type 3 PROFIBUS DP
specifications
–– -40°C to +125°C temperature range for
use in extreme conditions
•• Space-saving
–– Tiny 8-pin, 3mm x 3mm TDFN package
•• Industry’s highest ESD protection
improves reliability
–– ±35kV Human Body Model (HBM)
–– ±20kV IEC 61000-4-2 (Air Gap)
–– ±10kV IEC 61000-4-2 (Contact)
RO
R
RE
A
SHUTDOWN
B
DE
DI
D
MAX14770E
Block diagram of the MAX14770E.
www.digikey.com/maxim-industrial
25
Programmable logic controllers (PLCs)
Fieldbus functions
RS-485 transceivers with integrated termination simplify equipment installation
MAX13450E*/MAX13451E*
Benefits
RS-485 half-duplex and full-duplex networks operating at high
data rates must have their transmission lines terminated at both
ends in order to minimize reflections from termination-impedance
mismatch. To perform the termination, typically discrete resistors are
either put into the equipment or added externally at the end-point
devices on the line. Most commonly, 120Ω transmission lines are
used in RS-485 applications. Recently, however, 100Ω lines have
become preferred because they use Ethernet cables.
•• Flexible configurations interface to
many applications, thus reducing
inventory
–– Pin-selectable 100Ω/120Ω termination
resistors eliminate external components
–– Pin-selectable slew-rate limiting
improves EMI performance
–– Integrated VL pin (down to 1.62V) allows
interfacing with mixed-voltage systems
The new RS-485 transceivers like the MAX13450E/MAX13451E
eliminate the need for external termination resistors because they
integrate pin-selectable 100Ω/120Ω resistors. The integrated logiclevel translation (VL pin) provides compatibility with mixed-voltage
systems. •• Integrated protection is ideal for harsh
environments
–– Thermal shutdown at +150°C
–– Fail-safe operation
–– High ±30kV (HBM) ESD protection
•• Robust, -40C to +125°C automotive
temperature grade
•• Fault output warns user of short circuits
Software-/pin-selectable
termination allows remote
network configuration
Switchable termination
eliminates external resistors
and DIP switches
MAX13451E*
D
MASTER
SLAVE 1
SLAVE 2
END SLAVE
R
Integrated termination
resistors support both
100Ω and 120Ω cables
RS-485 transceivers integrate all functions needed for robust industrial communications.
* Future product—contact factory for availability.
26
Maxim Industrial Solutions
Programmable logic controllers (PLCs)
Fieldbus functions
Isolated RS-485 transceiver reduces BOM complexity
MAX3535E
Benefits
Galvanic isolation between the PLC’s backplane and the fieldbus
is required due to the harsh conditions and large common-mode
voltages that can occur between remotely located subsystems.
Maxim offers RS-485 transceivers with integrated isolation based on
capacitors, transformers, and optical techniques.
•• Eliminates the need for external
isolation circuitry
–– 2500VRMS RS-485 bus isolation using
on-chip high-voltage capacitors
•• High-ESD protection up to ±15kV ESD
–– 3.0V to 5.5V operation for interfacing
with multivoltage systems
The MAX3535E RS-485 transceiver is designed for applications where
galvanic isolation is required up to ±2500V. By integrating the full
half-bridge driver and rectifier, the MAX3535E offers ease of use. It
provides extended ESD protection up to ±15kV. 2
ST1
1 VCC
10µF
28
27
26
25
3
11
ST2
14
GND2 VCC2
420kHz
MAX3535E
VOLTAGE
REGULATOR
A
RO
R
RE
RO2
DE
Y
DI
D
4 GND1
16
B 15
Z
SLO
TWISTED-PAIR
CABLE
17
13
12
18
RS-485/RS-422 BUS
Block diagram of the MAX3535E. Dashed line signifies isolation barrier.
www.digikey.com/maxim-industrial
27
Programmable logic controllers (PLCs)
Fieldbus functions
Fault-protected RS- 485 transceivers make equipment more robust
MAX13448E, MAX3440E–MAX3444E,
MAX13442E/MAX13443E/MAX13444E, MAX3430
Benefits
•• Reduce board space by 25% with
integrated fault-protection circuitry
In applications where power and data are distributed over the same
cable, there is a potential for miswiring, cable shorts, or surges on
the communication bus. Maxim’s RS-485 MAX13448E, MAX13442E,
MAX3430, and MAX3440E transceiver families offer fault protection
up to ±80VDC. •• Highest fault protection from an
integrated transceiver
–– Fault protection up to ±80VDC
•• Flexible configurations allow
interfacing with multiple systems
–– Wide 3.3V to 5V supply range allows
interfacing with full- and half-duplex
RS-485
•• High integration reduces Bill of
Materials (BOM) complexity
–– Slew-rate limiting facilitates error-free
data transmission
–– True fail-safe operation
–– Hot-swap capability
•• ESD protection up to ±15kV (HBM)
Reduces
external components,
saves up to 25%
board space
DE
VCC
DE
Y
DI
Y
DI
D
Z
Z
MAX13448E
DI
A
RO
B
N.C.
A
R
B
GND
RE
RE
ZENERS
POLYSWITCH
LIMITERS
Part
VCC Supply (V)
Configuration
Fault Protection (V)
3.3 to 5
Full
±80
MAX3440E–MAX3444E
5
Half
±60
MAX13442E–MAX13444E
5
Half
±80
3.3
Half
±80
MAX13448E
MAX3430
Maxim’s RS-485 family offers high levels of integration which saves board space and reduces cost.
28
Maxim Industrial Solutions
Programmable logic controllers (PLCs)
Fieldbus functions
Industry’s smallest RS-485 transceivers save board space and reduce BOM complexity
MAX13485E/MAX13486E, MAX13430E–
MAX13433E
Benefits
MAX13485E/MAX13486E
•• Smallest footprint enables compact
designs
–– Space-saving, tiny 8-pin μDFN (2mm x 2mm) package
As industrial modules become smaller, pressure mounts for PLC
designers to shrink their PCBs and transition from the traditional
industry-standard packages like SO, SSOP, and PDIP. Maxim offers
a full family of RS-485 transceivers available in tiny µDFN/TDFN
packages with integrated features that reduce BOM complexity,
board space, and cost. •• High integration reduces BOM
complexity
–– Hot-swap operation eliminates false
transitions during power-up/live
insertion
–– Enhanced slew-rate limiting facilitates
error-free data transmission
–– Low-power shutdown modes reduce
power consumption during idle
operation
Extended ESD protection
for I/O pins (±15kV, HBM)
Hot-swappable for
telecom applications
VCC
0.1µF
RO 1
8
RE 2
7
SHDN 3
MAX13485E
DI 4
B
GNDISO
A
6
MAX13430E–MAX13433E
•• Smallest footprint enables compact
designs
–– Available in tiny 10-pin TDFN/µMAX®
(3mm x 3mm) packages
VCC
5
GNDISO
Packaged in a µDFN, the MAX13485E saves more than 50% board space compared to the competition.
VCC
VL
MAX13432E
MAX13433E
MAX13430E
MAX13431E
DI
DI
D
DE
B
RE
A
RO
VCC
VL
R
GND
D
DE
RE
RO
R
•• Flexible configurations for interfacing
to many applications, thus reducing
inventory
–– Wide 3V to 5V supply reduces need for
5V supply
–– Integrated VL pin allows interface with
low-voltage logic (down to 1.62V logic)
field-programmable gate arrays (FPGAs)
Z
and application-specific ICs (ASICs)
Y
–– Enhanced slew-rate limiting facilitates
error-free data transmission
–– High ±30kV (HBM) ESD protection
provides the industry’s most robust
protection
B
A
GND
Typical operating circuits of the MAX13430E product family.
www.digikey.com/maxim-industrial
29
Programmable logic controllers (PLCs)
Fieldbus functions
Advanced SPI/I2C UART enhances system flexibility and functionality, reduces load on
the microcontroller
MAX3107
Benefits
The MAX3107 serial UART bridges SPI or I2C to an asynchronous
communication interface like RS-485, RS-232, PROFIBUS DP, or IrDA®.
RS-485 and PROFIBUS DP work up to high data-rates which many
UARTs embedded on today’s microcontrollers cannot support. With
two 128-word FIFOs and an integrated oscillator, this UART requires
only a simple host controller for high-speed operation. Working at
these high rates, the MAX3107 supports today’s demanding highspeed applications.
•• Reduces cost of high-speed communication interfaces
–– 128-byte FIFOs
–– Automatic half-duplex transceiver
control –– High 24Mbps (max) data rates
•• High integration saves cost and space
–– Integrated oscillator reduces need for an
external crystal
•• Advance on-board clocking allows
near-limitless baud-rate generation
–– Integrated PLL, divider, and a fractional
baud-rate generator yield high accuracy
and freedom in baud-rate programming •• Enables high density and compact PLC
designs
–– Tiny 24-pin, TQFN (3.5mm x 3.5mm) and
standard SSOP packages
3.3V
0.1µF
VA
LDOEN
VEXT
VL
TX
I2C/SPI
RTS/CLKOUT
10kΩ
IRQ
MICROCONTROLLER
MAX3107
RX
DI
A
DE
B
RO
RE
XOUT
SPI
RST
AGND
V18
XIN
DGND
MAX14840
0.1µF
The MAX3107 in an RS-485 half-duplex application.
30
Maxim Industrial Solutions
Programmable logic controllers (PLCs)
Digital I/O functions
Digital I/O functions
Overview
communication link is higher than
typically found with analog communication. Consequently digital I/O
functions allow longer cable runs at
low data rates.
Digital I/Os interface to industrial
sensors and actuators and communicate with digitized information. The
sensors and actuators are located in
the field and, thus, are represented
on the lowest level of the control
system’s hierarchy. In contrast to
analog I/O modules, digital I/O
modules send or receive digitized
information, which is either 1-bit
(binary) information or quantized
values. The information flow can be
uni- or bidirectional, depending on
the interface type.
Interface types
Common digital interfaces are 24V
digital I/Os. The 24V digital interfaces
are unidirectional and based either
on two-, three-, or four-wire cabling.
A 24V digital I/O provides both the
24V and ground supplies to the
sensor/actuator, as well as one or two (unidirectional) data lines.
There is a significant advantage to
using digitized information: digitized
data is more tolerant of noise. This is
important, because interference on
the programmable-logic-controller
IO-Link® is a new sensor/actuator
interface technology based on 24V
I/Os. In an IO-Link system the data
line is bidirectional and supports
data rates up to 230kbps. The IO-Link
HOT-SWAP
CONTROLLER
point-to-point interface connects
one sensor or actuator to one digital
I/O port. Remote configuration,
diagnostics, and monitoring of the
peripherals is are enabled with intelligent and configurable sensors.
The CompoNet® network uses RS-485
differential signaling to communicate with sensors and actuators
at high data rates. A master-slave
network, CompoNet allows one
master to control up to 384 slaves.
Optional 24V powering of up to 5A
is allowed over the same cable. The
sensors and actuators are typically
powered by a 24V supply, which is
isolated from the system’s backplane.
This function is shown on the block
diagram in the Isolated power-supply
functions section below.
ISOLATED POWER SUPPLY
IO-Link
RS-485
CompoNet
CAN
CONTROLLER
TO/FROM
SENSORS,
ACTUATORS,
HMI
UART
WIRELESS
DIGITAL INPUTS
DIGITAL OUTPUTS
THERMAL
MANAGEMENT
COMPARATORS
VOLTAGE MONITORS
SWITCH
DEBOUNCER
POWER-LINE
COMMUNICATIONS
= MAXIM SOLUTION
With an industrial digital I/O interface, 1-bit or quantized data flow to and from the sensors and actuators is easy.
For a list of Maxim's recommended PLC solutions, please go to: www.maxim-ic.com/plc.
www.digikey.com/maxim-industrial
31
Programmable logic controllers (PLCs)
Digital I/O functions
IO-Link master transceiver enables high-density IO-Link masters
MAX14824*
Benefits
The MAX14824 is an IO-Link master transceiver designed for highchannel-count IO-Link port-count applications. The MAX14824 integrates an IO-Link physical interface with an additional digital
input and two regulators. A high-speed 12MHz SPI interface allows
fast programming and monitoring of the IO-Link interface. A slave
transceiver is located on the sensors/actuators.
•• Optimal digital I/O solution lowers cost
for high-port-count IO-Link systems
–– SPI in-band addressing reduces
hardware costs
–– Digital input enables high-density, digital-input designs
The MAX14824’s in-band addressing and selectable SPI addresses
enable multiple devices to be cascaded. The device supports the
standard IO-Link data rates and features slew-rate selection to
reduce EMI. The driver is guaranteed to drive up to 300mA (min) load currents. Internal wake-up circuitry automatically determines
the correct wake-up polarity, thus allowing the use of simple UARTs
for wake-up pulse generation. The MAX14824 is available in a 4mm x 4mm, 24-pin TQFN and operates over the extended -40°C to +85°C temperature range.
•• High-power drive allows use in digital
outputs
–– 300mA drive current drives high-power
valves
•• High integration reduces load on
processor
–– Automatic wake-up generation allows
use of simple processors
24V
0.1μF
0.1μF
1μF
VCC
VL
IRQ
SS
IO-Link
CONTROLLER
GND
V33
V5 LDOIN
VCC
IRQ
CS
SCLK
SCLK
MOSI
SDI
MISO
SDO
RX
Rx
TX
TxC
RTS
TxEn
GPO
WuEn
GPI
TxQ
LI
C/Q
MAX14824
MASTER TRANSCEIVER
DI
A0
A1
A2
A3
GND
A MAX14824 block diagram of an IO-Link transceiver interfacing to an IO-Link controller to enable 24V, high-speed,
bidirectional digital communication.
* Future product—contact factory for availability.
32
Maxim Industrial Solutions
Programmable logic controllers (PLCs)
Digital I/O functions
Simplest, most economical solution for high-port-count IO-Link systems
MAX14830*
Benefits
The MAX14830 is an advanced quad, serial UART with 128-word FIFOs
for high-port-count I/O systems like an IO-Link system. By reducing
the number of signals that need be isolated, the serial I2C/SPI host
interface is optimized for industrial systems that require galvanic
isolation. Many advanced UART and transceiver control features
remove timing-critical tasks from the host controller.
•• Intelligent features lower BOM cost
–– A scalable architecture based on only
one host controller eases software
development and reduces cost
–– Handles most low-level transceiver
control autonomously, reducing the
need for powerful and expensive
controllers
–– Reduces isolation needs, which
eliminates the need for expensive
isolation components
–– Small 48-pin, 7mm x 7mm TQFN
package enables small, high-port-
count systems
CONTROLLER
MISO
MOSI
SCLK
CS1
CS2
RST
ISOLATION
MAX14824*
Rx
TxC
TxEn
PORT 1
PHY
ADDR 1
Tx0
Rx0
RTS0
MAX14824*
Rx
TxC
TxEn
PORT 2
PHY
Tx1
Rx1
RTS1
ADDR 2
MAX14830
QUAD UART
MAX14824*
Tx2
Rx2
RTS2
Tx3
Rx3
RTS3
Rx
TxC
TxEn
ADDR 3
MAX14824*
Rx
TxC
TxEn
Block diagram of the MAX14830 quad UART.
PORT 3
PHY
•• Advanced clocking scheme simplifies
baud-rate generation
–– Internal oscillator reduces need for
external crystal and lowers cost
–– Integrated PLL, divider, and fractional
baud-rate generator allow considerable
flexibility in baud-rate programming
and independence of reference clock,
thus simplifying clock design
–– Four timers produce programmable
clock outputs, which mitigate the need
for and cost of LED blinking
PORT 4
PHY
ADDR 4
* Future product—contact factory for availability.
www.digikey.com/maxim-industrial
33
Programmable logic controllers (PLCs)
CPU functions
CPU functions
Overview
The CPU functions for a PLC include
the processor, memory, and support
circuitry required to execute the
programmed instructions and
communicate with the various I/O functions.
System monitoring functions are
performed by the CPU’s powersupply voltage monitors; watchdog
timers (WDTs) and reset circuits;
and thermal monitors for critical
devices and hot spots. The CPU
module also includes components
to enable communications to other
modules, PLCs, PCs, and the human
interface (e.g., switch debounce,
displays, audio). Isolated power
supplies, hot-swap controllers, and
battery backup combine for power
management.
components include security
managers with tamper detection and nonimprinting memory, secure
microcontrollers with authentication,
and 1-Wire® authentication devices
with an integrated SHA-1 algorithm.
Secure components require several
specific features, including tamper
detection; fast-erasing memory for
storage of secret data; analysis-
resistant encryption engines; and
support for PCI PED 2.1, FIPS 140.2
(level 3 and above), EMV® 4.1, and
Common Criteria requirements.
Security functions
Security and authentication components prevent unauthorized system
control or access to system data. The
complexity of security components
varies depending on the level of
security required. Typical security
DISPLAY
DRIVERS
TO DISPLAY
BACKLIGHT
WATCHDOG
TIMER
RESET ICs
TOUCH SCREEN
AUDIO OUTPUT
AUDIO AMPLIFIER
µP
CPU
FPGA
VOLTAGE
MONITORS
FILTERS
CODECS
SECURE-µP
THERMAL
MANAGEMENT
SECURITY MANAGER
CLOCK
USB
SWITCH
DEBOUNCER
HOT-SWAP
CONTROLLER
1-WIRE INTERFACE
AND
AUTHENTICATION
TO ALL
BATTERY
BACKUP
ISOLATED POWER SUPPLY
= MAXIM SOLUTION
Block diagram of PLC CPU functions. For a list of Maxim's recommended PLC solutions, please go to: www.maxim-ic.com/plc.
34
Maxim Industrial Solutions
Programmable logic controllers (PLCs)
CPU functions
Smallest secure microcontroller minimizes system size
MAXQ1850
Benefits
The MAXQ1850 is the industry’s smallest, high-security microcontroller. This single-cycle RISC processor executes 16-bit instructions
and uses a 32-bit data path for unmatched processing efficiency
and C code optimization. With hardware-accelerated symmetric
and asymmetric encryption routines, it has the flexibility to be a
stand-alone controller or a coprocessor depending on the secure
application’s requirement.
•• Improve system security
–– Cryptographic hardware accelerators
for RSA, DSA, ECDSA, SHA-1, SHA-2, AES,
DES, and 3DES
–– Security supervisor provides tamper
detection and response
–– Cryptography engine execution at
65MHz
System cost is highly optimized with integrated active tamper
sensors. These sensors detect and react to attacks by erasing the
internal, secure 8KB battery-backed nonvolatile SRAM. The microcontroller only uses 130nA to back up the secure SRAM and operate
the tamper sensors.
•• Smallest board space requirement
–– 6mm x 6 mm, 40-pin TQFN package
–– 7mm x 7mm, 49-ball CSBGA package
CORE
JTAG
OSC/PLL
MAXQ1850
16KB
ROM
MMU
MAXQ30
32-BIT
RISC CORE
AES
USER ENGINE
TIMERS/
COUNTERS
DES/3DES
USER ENGINE
POWER
MANAGEMENT
INTERRUPT
CONTROLLER
2048-BIT MAA
(RSA, DSA, ECDSA)
8KB
SECURE
NV SRAM
256KB
FLASH
SHA-1, SHA-2
WATCHDOG
CRC-16/32
GENERATOR
UNIQUE ID
ENVIRONMENTAL
SENSORS
EXTERNAL SENSOR
CONTROLLER
ISO 7816
USART
SECURE RTC
SPI
RNG
USB
GPIOs
Block diagram of the MAXQ1850.
www.digikey.com/maxim-industrial
35
Programmable logic controllers (PLCs)
CPU functions
Security managers protect encryption keys from intruders
DS3600
Benefits
Security managers provide comprehensive data protection. The
DS3600 single-chip solution provides security, tamper detection,
encryption key storage, and encryption key destruction in the event
of tampering. The DS3600 is packaged in a CSBGA for an added level
of security.
•• Improved system security
–– Supports the highest security-level
requirements of the FIPS 140.2, Common
Criteria, PCI PED, and EMV 4.1 certification agencies
–– Multilevel tamper detection
–– Keys and/or other critical data are
immediately and completely erased as a response to a qualified tamper
–– Patented on-chip nonimprinting
memory*
32.768 kHz
X1
VCCO
VCC
VCCI
BATTERY
VBAT
X2
IN1+
USER-DEFINED TAMPER
SENSOR/VOLTAGE
MONITORING
OPTIONAL
POWER-MANAGEMENT LOGIC
BAT-ON
IN3-
DAT
PX.0
CLK
PX.1
CE
PX.2
RST
RST
VCC0
VBAT
CEI
CE
IN2+
USER-DEFINED
RESISTIVE MESH
HOST CPU
WITH
INTERNAL MEMORY
INT
WE
DS3600
RD
A0-Ax
D0-Dx
IN4TOUT
OE
DS3690
TRANSMISSION GATE
USER-DEFINED EXTERNAL
TAMPER CIRCUITRY
TAMP
CASE SW
WE
CSW
SERVICE SW
SSW
CBAT
CAP-
VRAM
VCC
CEO
CE
RD
A0-Ax
D0-Dx
EXTERNAL SRAM
CAP+
470kΩ
(typ)
470kΩ
(typ)
1μF 10V (typ)
VCCO
The DS3600 secure supervisor in a typical security application.
*U.S. Patent #7,379,325.
36
Maxim Industrial Solutions
Programmable logic controllers (PLCs)
CPU functions
1-Wire SHA-1 authenticators securely protect control modules from unauthorized
cloning or feature modification
DS28E01-100, DS28E02, DS28E10
Benefits
1-Wire secure memories utilize a SHA-1-based, crypto-strong, secure
challenge-and-response authentication sequence. Thus authentication enables FPGAs and CPUs to differentiate between authorized
and cloned environments. The determination of authorized or cloned
either sets the system to normal operation, or disables the module
to protect the design investment from being copied. Additionally,
module operational features set with EPROM data values are SHA-1
protected against unauthorized modification.
•• Improved system security
–– Crypto-strong authentication based on
FIPS 180-3-defined SHA-1
–– Sophisticated physical security protects
against die-level attacks
–– Protected NV EPROM or one-timeprogrammable (OTP) memory for data
storage
–– Optional, confidential preprogramming
of customer-defined secure data by
Maxim*
•• Minimal I/O pin and resource impact on
the FPGA or CPU design
–– Consumes only one I/O pin for total
operation
–– Single dedicated contact for communication and power
–– Small code/gate/memory footprint for
CPU and FPGA implementation
Upon power-up, the FPGA sends
a random challenge to the secure
memory, which responds with a
SHA-1 MAC corresponding to the
random challenge.
µP
1-Wire
SECURE
MEMORY
FPGA
FLASH
MEMORY
The FPGA compares the expected
response to the actual response and
tells the µC which system setting to
apply (including disable).
Block diagram of FPGA secure authentication using a 1-Wire secure memory device.
* For more information, please see: application note 4594, “Protect Your FPGA Against Piracy: Cost-Effective Authentication Scheme Protects IP in SRAM-Based FPGA Designs”;
application note 3826, “Xilinx ® FPGA IFF Copy Protection with 1-Wire ® SHA-1 Secure Memories”; and 1-Wire FPGA Security Flash™ Tutorial FPGA Security, Flash™ tutorial.
www.digikey.com/maxim-industrial
37
Programmable logic controllers (PLCs)
Isolated power-supply functions
Isolated power-supply functions
Overview
Power functions
Typically PLCs have a backplane
power rail of about 24V DC, although
the actual voltage can differ, usually
from 12V to 48V. The power comes
from an isolated DC-DC converter
connected to a factory AC-DC supply. A PLC can be equipped with an
auxiliary battery with a special
OR-ing controller. Together, this
configuration forms an uninterruptable power supply (UPS) to ensure
continued operation in the event of
an AC power-line brownout or failure.
During AC faults the battery supplies
the power rail to the backplane.
The whole PLC power network is
quite complicated with a variety of protection, isolation, and postregulation functions. This power
function can also be duplicated in a
system to allow hot backup and hotswapping in case of a power fault.
PLC functions take power from the
power rail and are organized into
separate functional modules that
have hot-swap controllers to prevent
inrush current surges during hot
installation/removal. The modules’
power inputs can usually withstand
GALVANIC
ISOLATION
BARRIER
I/O CARDS
GALVANIC
ISOLATION
BARRIER
CPU
VOLTAGE TO
FIELD
INTERFACE
MODULE
CURRENT
LIMITER
VOLTAGES
VOLTAGES
ISOLATED
I/O
POWER
ISOLATED
I/O
POWER
a higher voltage than the power rail,
because high-voltage spikes can
occur at those inputs. Each functional
module has its own local converters
to generate regulated 5V, 3.3V,
and other local power rails. The
CPU typically requires even lower
voltages for a high-performance
controller’s core and/or FPGA. Analog
I/Os can require ±15V or higher
voltages for op amps and/or analogoutput conditioners. A PLC can also
provide a regulated power output of
24V for smart sensors, other remote
equipment, and analog current-loop
interfaces.
ISOLATED
INTERFACE
POWER
DC-DC
POWER
ISOLATED
FIELD POWER
INDUSTRIAL DC BUS
PRECISION
RESISTORS
DIGITAL
POTENTIOMETER
VOLTAGE
MONITORS
BACKUP BATTERY
MANAGEMENT
THERMAL
MANAGEMENT
OVERVOLTAGE
PROTECTION
HOT-SWAP
CONTROLLER
MOSFET/
RECTIFIER DRIVER
CALIBRATION, MARGINING, AND
ADJUSTMENT
PUSHBUTTON
CONTROLLER
= MAXIM SOLUTION
Block diagram of isolated power-supply functions. For a list of Maxim's recommended PLC solutions, please go to: www.maxim-ic.com/plc.
38
Maxim Industrial Solutions
Programmable logic controllers (PLCs)
Isolated power-supply functions
Simplify industrial-bus power design with integrated hot-swap controllers and FETs
that power devices
MAX5042/MAX5043
Benefits
The MAX5042/MAX5043 are isolated, multimode, pulse-widthmodulated (PWM) power ICs. They feature integrated switching
power MOSFETs connected in a voltage-clamped, two-transistor,
power-circuit configuration. These devices operate from a wide
20V to 76V input voltage range. The MAX5042 includes a hot-swap
controller to plug into a live power backplane with a MAX5058/
MAX5059 rectifier driver. Operating at up to a 500kHz switching
frequency, these devices provide up to 50W of output power.
•• Eliminate external components to
simplify power design
–– Connect directly to the industrial
backplane across a wide voltage range
•• Cut costs by eliminating external
hot-swap controller and switch
VIN+
32V TO 72V
C1
220µF
100V
R12
200kΩ
1%
C30
0.68µF
100V
POSINPWM
C3
1µF
C9
C12
220pF 0.1µF
R13
1MΩ
R14
10kΩ
DRNH
RAMP
RCFF
REG9
DRVIN
FLTINT
DRVDEL
SYNC
R22
10kΩ
UVLO
BST
XFRMRH
R20
10kΩ
XFRMRL
MAX5042
T1
R11
20Ω
1%
C16
0.001µF
R9
15Ω
D4
D2
L1
4.4µH
5V
8A
C17
150µF
6.3V
C18
150µF
6.3V
SGND
C7
1µF
CSP, SRC
RCOSC HSEN CSS
R15
24.9kΩ
1%
NEGIN HSGATE
R10
33mΩ
1%
C14
100pF
C20
0.1µF
100V
NEGIN
R4
10Ω
PWMNEG,
HSDRAIN CSN PWMPNEG OPTO
C11
0.1µF
C4
0.1µF
C5
0.0047µF
REG15
REG5
C13
1µF
C6
0.1µF
U1
PWMSD
C25
0.22µF
D3
D1
R3
150Ω
1%
C19
0.15µF
N1
(HOT-SWAP MOSFET)
R21
1.24kΩ
1%
C8
0.33µF
E
R6
200Ω
1%
LED
U2
FOD2712
FB
C15
0.1µF
R1
25.5kΩ
1%
R2
8.25kΩ
1%
COMP
C
GND
R5
10Ω
1%
MAX5042 typical application circuit, a 48V power supply with hot-swap capability.
www.digikey.com/maxim-industrial
39
Programmable logic controllers (PLCs)
Isolated power-supply functions
Reduce system downtime with current-mode PWM controller with integrated
hot-swap
MAX5069
Benefits
The MAX5069 is a high-frequency, current-mode PWM controller
with dual MOSFET drivers. The IC integrates everything necessary
for implementing AC-DC or DC-DC fixed-frequency power supplies.
Isolated or nonisolated, push-pull and half-/full-bridge power
supplies are easily constructed using either primary- or secondaryside regulation. An input undervoltage lockout (UVLO) programs the
input-supply startup voltage and ensures proper operation during
brownout conditions. The MAX5069 operates at over 100W.
•• Simplifies design by supporting highload currents
•• Cut costs by eliminating external
hot-swap controller and switch
VOUT
C7
VIN
R1
C1
R6
R2
IN
C2
UVLO/EN
FLTINT
C3
VCC
RHYST
MAX5069B
HYST
R7
C4
REG5
NDRVB
R3
Q2
RT
NDRVA
R4
DT
CS
SCOMP
FB
C5
AGND
Q1
R12
R8
C8
VCC
PGND COMP
R5
C10
C6
R10
R9
R13
PS2913
R11
MAX8515
R14
Secondary-side, regulated, isolated power supply. The dashed line encompasses both functions of the optoisolator.
40
Maxim Industrial Solutions
Programmable logic controllers (PLCs)
Isolated power-supply functions
Save space and costs by integrating three switching controllers
MAX15048/MAX15049
Benefits
The MAX15048/MAX15049 are triple-output, PWM, step-down DC-DC
controllers with tracking (MAX15048) and sequencing (MAX15049)
options. The devices operate over the 4.7V to 23V input voltage
range. Each PWM controller provides an adjustable output down to
0.6V and delivers up to 15A of load current with excellent load and
line regulation. The options of coincident or ratiometric tracking
(MAX15048) or output sequencing (MAX15049) allow tailoring of
the power-up/power-down sequence, depending on the system
requirements.
•• Simplify design of power supplies for
CPUs and FPGAs with built-in tracking
and sequencing
•• Handle high-load currents seamlessly
with an external switch
VOUT2
IN
EN2
FB2
COMP2
PGND2
DL2
LX2
BST2
DH2
IN
IN
EN1
IN
DH3
VOUT3
LX3
DH1
BST3
LX1
DL3
BST1
MAX15048
PGND3
DL1
FB3
VOUT1
VOUT1
COMP3
PGND1
PGOOD
REG
RT
SGND
FB1
EN3
COMP1
VREG
VOUT1
VOUT2
VOUT3
SOFT-START
SOFT-STOP
COINCIDENT TRACKING OUTPUTS
Typical operating circuit of the MAX15048.
www.digikey.com/maxim-industrial
41
Programmable logic controllers (PLCs)
Isolated power-supply functions
Save cost with integrated DC-DC converters that power off an industrial bus
MAX5080/MAX5081
Benefits
The MAX5080/MAX5081 are 250kHz, PWM, step-down DC-DC
converters with an on-chip high-side switch. The input voltage range
is 4.5V to 40V for the MAX5080 and 7.5V to 40V for the MAX5081.
The devices’ output is adjustable from 1.23V to 32V and can deliver
up to 1A of load current. Both devices utilize a voltage-mode control
scheme for good noise immunity in a high-voltage switching environment. External compensation allows maximum flexibility
with a wide selection of inductor values and capacitor types.
•• Simplify design by connecting directly
to an industrial power backplane
VIN
4.5V TO 40V
D1
CF
IN
DVREG
C-
•• Save cost by integrating switches and
voltage-mode controller
CBST
BST
C+
R1
L1
LX
VOUT
C6
REG
C1
ON/OFF
SYNC SGND PGND
R2
FB
SS
PGND
R6
C8
COMP
R5
C2
R3
C5
D2
MAX5080
C7
R4
CSS
PGND
Typical operating circuit for the MAX5080.
42
Maxim Industrial Solutions
Programmable logic controllers (PLCs)
Isolated power-supply functions
OR-ing FET controller supports main and battery-backup power to improve
system reliability
MAX5079
Benefits
The MAX5079 OR-ing MOSFET controller replaces OR-ing diodes
in high-reliability, redundant, parallel-connected power supplies.
The controller allows the use of low-RON, n-channel power MOSFETs
to replace Schottky diodes. The MAX5079 operates from 2.75V to
13.2V and includes a charge pump to drive the high-side n-channel
MOSFET. Operating over the -40°C to +85°C temperature range, the
MAX5079 is available in a space-saving 14-pin TSSOP package.
•• Eliminates expensive external
components
–– Build redundant systems without the
power-dissipation disadvantages of
Schottky diodes
•• Reduces costs
–– Low-power dissipation
–– Smaller size in space-saving TSSOP
package
–– Eliminates heatsinks for high-power
applications
SUB 75N 03-04
VOUT1
POWER SUPPLY 1
(PS1)
1V TO 13.2V
VBUS
N1
BUS
COMMON
VIN
>2.75V
IN
GATE
UVLO
STH
RSTH
CSTH
C+
BUS
U1
AUXIN
PGOOD
OVI
MAX5079
C-
FTH
OVP
GND
RFTH
CEXT
SUB 75N 03-04
VOUT2
POWER SUPPLY 2
(PS2)
1V TO 13.2V
VBUS
N2
VIN
>2.75V
IN
GATE
AUXIN
U2
UVLO
STH
RSTH
CSTH
C+
MAX5079
C-
CEXT
BUS
CBUS
PGOOD
FTH
OVI
OVP
GND
RFTH
Typical operating circuit for the MAX5079 supporting a main and backup power supply.
www.digikey.com/maxim-industrial
43
Programmable logic controllers (PLCs)
Isolated power-supply functions
Simplify isolated power-supply design with a highly integrated transformer driver
MAX256
Benefits
For systems that require a low-watt, isolated power supply, a typical
closed-loop switching regulator can add unnecessary cost and
complexity. The MAX256 simplifies an isolated power-supply design.
It is easily used for implementing an unregulated, full-bridge forward
converter with an output power of up to 3W from an input voltage of
3V to 5.5V.
•• Integrated protection circuitry prevents
system-level failures
–– Thermal shutdown
–– Undervoltage lockout (UVLO)
–– Watchdog protection in clock circuitry
The device integrates an on-board oscillator, protection circuitry,
and internal FET drivers to provide up to 3W of power to the primary
winding of a transformer. The MAX256 operates with an internal
programmable oscillator, or it can be driven by an external clock for
improved EMI performance. The MAX256 is available in an 8-pin,
thermally enhanced SO package. The device is specified for the -40°C to +125°C automotive temperature range.
•• Internal/external clocking modes allow
system performance to be optimized
–– Integrated internal oscillator eliminates
the need for an external clock/oscillator
–– External clock-synchronization mode
improves EMI performance
•• Integrated push-pull drivers reduce
BOM complexity and board space
+5V
4.7µF
470nF
MAX256
ST1
1:2.6CT
+5V ISOLATED
0.1µF
MODE
ST2
CK_RS
47kΩ
GND
The MAX256 can be used in an unregulated 3W power supply.
44
Maxim Industrial Solutions
Programmable logic controllers (PLCs)
Recommended solutions
Recommended solutions
Analog input function
Part
Description
Features
Benefits
Active filters
MAX7409/10
5th-order, switched-capacitor, lowpass
filters (Bessel or Butterworth)
Clock or capacitor-adjustable corner frequency
to 15kHz; 1.2mA supply current
Save space over discrete implementations
MAX7422–MAX7425
5th-order, switched-capacitor, lowpass
filters (elliptic, Butterworth, or Bessel)
Clock or capacitor-adjustable corner frequency to
45kHz; 3mA supply current; 8-pin µMAX package
Save space over discrete implementations
MAX274/75
4th-order/8th-order, 150kHz/300kHz
lowpass/bandpass filters
Resistor programmable; continuous-time filters;
-86dB THD
Ease anti-aliasing filtering
MAX11040
24-bit, 4-channel, simultaneous-sampling
sigma-delta ADC
64ksps; internal reference; 38-pin TSSOP
package
Reduces firmware complexity, capturing
accurate phase and magnitude information
on up to 32 channels
MAX11200*–MAX11203*,
MAX11205*–MAX11213*
24-/20-/18-/16-bit, ultra-low power,
single-channel, delta-sigma ADCs with
internal buffers
3V supply; 0.45mW, industry-leading effective
Four integrated GPIOs save cost by
resolution per unit power; 16-pin QSOP package eliminating isolators between multiplexer
and microcontroller
MAX1162
MAX1167/68
16-bit, 200ksps, 1-/4-/8-channel SAR
ADCs
16 bits, no missing codes; single 5V supply;
Low 12.5mW power dissipation preserves
unipolar 0V to 5V input range; tiny µMAX/QSOP battery life
packages
MAX1300*/01/ 02*/03
16-bit, 8-/4-channel SAR ADCs with
software-programmable input ranges
115ksps; up to ±12V bipolar input range or
down to 0 to 2.048V unipolar range; ±16.5V
overvoltage protection (OVP)
Software-programmable input ranges save
design time, eliminate external circuitry
MAX1402/03
18-bit, 5-channel, sigma-delta ADCs
4.8ksps; 0.75mW; 28-pin SSOP package
Precision current-output sources eliminate
signal-conditioning circuitry
MAX5924/25/26
1V to 13.2V hot-swap controllers require
no RSENSE
Need no sense resistor; hot-swap voltage rails
down to 1V
Save cost and board space; hot-swap wide
1V to 13.2V range of supplies
MAX5932
Positive high-voltage, hot-swap controller
Hot swaps 9V to 80V supplies; overcurrent,
overvoltage, and undervoltage protection; pin
and function compatible with LTC1641-1
One device accommodates wide range
of backplane supply voltages; provides
robust protection against overcurrent,
undervoltage, and overvoltage faults
MAX5943
7.5V to 37V hot-swap controller with diode
OR-ing
Integrates low-voltage-drop OR-ing and hotswap function; programmable current-limit/
circuit-breaker function; UL® -recognized
FireWire ®/IEEE 1394™ protective circuit
Integrated hot-swap and diode OR-ing
function save space; robust/proven solution
passed UL testing and is proven for FireWire
applications
MAX4578/79
Midvoltage, single 8:1/dual 4:1 calibration
multiplexers
Dual ±20V supply; on-chip gain and offset
divider networks; low 0.005nA (typ) off-leakage
current
Integrated precision resistor-dividers allow
precision ADC calibration and system selfmonitoring
MAX354/55
Fault-protected analog multiplexers
Fault protection up to ±40V; 0.02nA (typ)
leakage currents; digital inputs are CMOS/TTL
compatible
High fault protection eliminates external
protection circuitry; pin compatible with
industry-standard DG508/DG509 for easy
upgrading
MAX14752/53
High-voltage 8:1 and dual 4:1 analog
multiplexers
Wide ±10V to ±36V (max) power-supply range;
60Ω (typ) on-resistance; low 0.03Ω (typ) RON
flatness over common-mode voltage
High supply voltage eliminates external
protection circuitry; pin compatible with
industry-standard DG408/DG409 for easy
upgrades
MAX7413/14
ADCs
Hot-swap controllers
Multiplexers
(Continued on next page)
*Future part—contact factory for availability.
www.digikey.com/maxim-industrial
45
Programmable logic controllers (PLCs)
Recommended solutions
Recommended solutions (continued)
Part
Description
Features
Benefits
Operational amplifiers
MAX9943/44
38V precision, single and dual op amps
Wide 6V to 38V supply range; low 100µV (max)
input offset voltage; drive 1nF loads
Wide operating voltage range and precision
performance under most capacitive loads
MAX9945
38V CMOS-input precision op amp
Wide 4.75V to 38V supply range; low input-bias
current; rail-to-rail output swing
High voltage and low femto-amp input-bias
current easily allow high-voltage interfacing
with ultra-high omhic sensors
MAX410/MAX412/
MAX414
28MHz, 10V, low-noise, precision, single/
dual/quad series op amps
2.4nV/√Hz; 250µV (max) offset; 28MHz gain
bandwidth (GBW)
High-accuracy signal conditioning at low
frequencies and at high gain
MAX4238/39
Industry’s lowest offset, low-noise rail-torail output op amps
2µV (max) offset; 25nV/√Hz; 6.5MHz GBW and
no 1/f input-noise component
Continuous precision signal conditioning at
low frequencies over time and temperature
MAX9939
SPI-programmable-gain amp (PGA) with
on-demand calibration and differential in/
out configurations
Input supports negative voltages; wide gainconfiguration range; input-error-nulling feature
Calibration on demand improves system
accuracy, minimizes harsh environmental
noise
MAX5490/91/92
Precision-matched thin-film resistordividers
Ratiometric 1ppm/°C (typ) temperature drift;
80V working voltage
Maintain system accuracy over temperature
variations; work well in high-voltage
applications
MAX5427/28/29
Low cost, one-time-programmable (OTP)
digital potentiometers with up/down
interface
1µA (max) standby current (no programming);
Increase power savings and provide better
35ppm/°C end-to-end and 5ppm/°C ratiometric measurement stability over temperature
tempco
changes
MAX5494–MAX5499
10-bit, dual, nonvolatile voltage-dividers or 1µA (max) standby current (no programming);
Improve power savings and increase
variable resistors with SPI interface
35ppm/°C end-to-end and 5ppm/°C ratiometric performance over temperature variations
tempco
Precision resistors
Signal conditioners
MAX1452
Low-cost, precision sensor signal
conditioner
Multitemperature calibration; current and voltage Highly accurate; simplifies designs in
excitation; fast 150ns response; single-pin
multiple platforms; reduces inventory and
programmable; 4–20mA applications
cost
MAX1464
Low-power, low-noise, multichannel, digital Integrated 16-bit ADC, DACs, and CPU;
sensor conditioner
programmable compensation algorithm; digital,
analog, and PWM outputs; 4–20mA application
Directly interfaces with microprocessors/
controllers; provides amplification,
calibration, linearization, and temperature
compensation for a variety of sensors
DS600
Precision, analog-output temperature
sensor
Industry’s highest accuracy: ±0.5°C from -20°C
to +100°C
Best cold-junction compensation accuracy
for superior thermocouple measurement
DS7505
Low-voltage, precision digital thermometer
and thermostat
±0.5°C accuracy from 0°C to +70°C; 1.7V to
3.7V operation; industry-standard pinout
Industry-standard pinout allows easy
accuracy upgrade and supply-voltage
reduction from LM75
MAX6631
Low-power, digital temperature sensor
±1°C accuracy from 0°C to +70°C; 50µA (max)
supply current
Low supply current extends battery life
MAX6675
K-type thermocouple-to-digital converter
Built-in cold-junction compensation
Simplest thermocouple interface; no
external components needed
MAX16023/24
Battery-backup switchover ICs with
integrated regulated output
Low power; small TDFN package; integrated
regulated output
Conserve power
MAX6381
Single-voltage supervisor
Multiple threshold and timeout options
Versatile for easy design reuse; saves space
in small modules
Thermal management
Voltage supervisors
(Continued on next page)
46
Maxim Industrial Solutions
Programmable logic controllers (PLCs)
Recommended solutions
Recommended solutions (continued)
Part
Description
Features
Benefits
Voltage supervisors (continued)
MAX6495
72V overvoltage protector
Protects against transients up to 72V; small,
6-pin TDFN-EP package
Increases system reliability by preventing
component damage due to high-voltage
transients; saves space; easy to use.
MAX6720
Triple-voltage supervisor
Two fixed and one adjustable thresholds
Integration shrinks design size
MAX6746
Capacitor-adjustable watchdog timer and
reset IC
Capacitor-adjustable timing; 3µA supply current
Versatile for easy design reuse; saves space
in small modules
MAX6816/17/18
Single/dual/octal switch debouncers
±15kV ESD protection
High reliability; easy to use
For a list of Maxim's recommended PLC solutions, please go to: www.maxim-ic.com/plc.
www.digikey.com/maxim-industrial
47
Programmable logic controllers (PLCs)
Recommended solutions
Recommended solutions (continued)
Analog output functions
Part
Description
Features
Benefits
HART
DS8500
HART modem
HART compliant; integrated digital filter; 5mm
x 5mm x 0.8mm TQFN package; 3.6864MHz
clock; 285µA active-mode current
Power-saving; single-chip solution with
small PCB foot print
32-channel sample/hold amplifier with
output-clamping diodes
2.5µs acquisition time; 0.01% accuracy of
acquired signal
Replaces 31 DACs, saving cost and space
MAX9943/44
38V high-output-drive, single and dual op
amps
Output voltage swing to 38V; output-current
drive exceeds 50mA; drives 1nF load
Easily drive 4–20mA loops at 24V
MAX4230–MAX4234
High-output-drive, 10Mhz, 10V/µs rail-torail input/output (RRIO) single/dual/quad
op amps
200mA peak current output; RRIO; consumes
only 1mA and drives 780pF
RF immunity design, output current and
slew rate ideal for driver applications, active
filters, or buffers
MAX4475–MAX4478
Low noise, low distortion, 10MHz single/
dual/quad op amps
Low THD+N (0.0002%); low 4.5nV/√Hz noise;
low offset voltage (350µV, max); up to 42MHz
GBW
Ideal to drive ADCs without adding
additional noise but maintaining the
effective number of system bits (ENOB)
MAX9650/51
High-current, high-voltage, RRIO, single
and dual op amps
20V operating voltage; 1.3A peak-current drive;
40V/µs slew rate
Handle system outputs in rugged industrial
environments
Demultiplexer
MAX5167
Operational amplifiers
Precision DACs
MAX5134–MAX5139
1-/2-/4-channel, 16-/12-bit DACs with pin- Output set to zero or midscale upon power-up
programmable zero or midscale power-up
Add additional safety during power-up
MAX5661
Single-channel DAC with 16-bit voltage- or 16-bit, current or voltage-buffered output;
current-buffered output
integrated high-voltage current and voltage
amplifiers; serial interface
Reduces external component count; reduces
cost
MAX5500
4-channel, 12-bit DAC with precision
amplifier-output conditioners
Output conditioners; 0.85mA of quiescent
current (IQ)
Needs no external amplifiers; makes
equipment more compact
Analog output conditioners
Programmable current (up to 24mA) and voltage Reduce board complexity by integrating
(up to ±10V) drive
current and voltage drive
MAX1452
Low-cost, precision sensor signal
conditioner
Multitemperature calibration; current and voltage Highly accurate; simplifies designs in
excitation; fast 150ns response; single-pin
multiple platforms; reduces inventory and
cost.
programmable; 4–20mA applications
MAX1464
Low-power, low-noise, multichannel, digital Integrated 16-bit ADC, DACs, and CPU;
Directly interfaces with microprocessors
sensor conditioner
programmable compensation algorithm; digital, and controllers; provides amplification,
analog, and PWM outputs; 4–20mA applications calibration, linearization, and temperature
compensation for a variety of sensors
Output conditioners
MAX15500/01
Signal conditioners
Thermal management
MAX6631
Low-power digital temperature sensor
±1°C accuracy from -0°C to +70°C; 50µA (max)
supply current
Very low supply current for minimal impact
on system power usage
DS7505
Low-voltage, precision digital thermometer
and thermostat
±0.5°C accuracy from 0°C to +70°C; 1.7V to
3.7V operation; industry-standard pinout
Industry-standard pinout allows easy
accuracy upgrade and supply voltage
reduction from LM75
(Continued on next page)
48
Maxim Industrial Solutions
Programmable logic controllers (PLCs)
Recommended solutions
Recommended solutions (continued)
Part
Description
Features
Benefits
Thermal management (continued)
DS18B20
Precision 1-Wire digital temperature sensor ±0.5°C accuracy; 1-Wire interface; 64-bit,
factory-lasered ID code
Connects multiple precision temperature
sensors with less wire than any competitive
solution
MAX16023/24
Battery-backup switchover ICs with
integrated regulated output
Low power; small TDFN package; integrated
regulated output
Conserve power
MAX6381
Single-voltage supervisor
Multiple threshold and timeout options
Versatile for easy design reuse; saves space
in small modules
MAX6495
72V overvoltage protector
Protects against transients up to 72V; small,
6-pin TDFN-EP package
Increases system reliability by preventing
component damage due to high-voltage
transients; saves space; easy to use
MAX6720
Triple-voltage supervisor
Two fixed and one adjustable thresholds
Integration shrinks design size
MAX6746
Capacitor-adjustable watchdog timer and
reset IC
Capacitor-adjustable timing; 3µA supply current
Versatile for easy design reuse; saves space
in small modules
Voltage supervisors
For a list of Maxim's recommended PLC solutions, please go to: www.maxim-ic.com/plc.
www.digikey.com/maxim-industrial
49
Programmable logic controllers (PLCs)
Recommended solutions
Recommended solutions (continued)
Fieldbus functions
Part
Description
Features
Benefits
Interface transceivers
MAX14770
PROFIBUS transceiver
±35kV (HBM) ESD tolerance; -40°C to +125°C
automotive temperature range; small (3mm x
3mm) TQFN package
Industry’s highest ESD protection makes
PLC more robust
MAX13450E/51E
RS-485 transceivers with pin-selectable
termination resistors
Integrated 100Ω and 120Ω termination resistors; Allow remote configuration of the line
FAULT indication; flexible logic interface
termination, which simplifies system
installation
MAX3535E
Isolated RS-485 transceiver
3V to 5V operation; 2500V RMS isolated RS-485/
RS-422 transceivers; ±15kV ESD protection
Eliminates the need for external isolation
components
MAX13442E/43E/44E
Fault-protected RS-485 transceivers
±80V fault protected half-duplex operation; 5V
transceivers (250kHz/10MHz)
Simplify design by eliminating external
components such as TVSs and PTCs
MAX13430E
RS-485 transceiver with V L pin in tiny µDFN 3.3V to 5V operation; integrated V L pin (down to
1.6V); 10-pin µMAX/µDFN packages
MAX253
Transformer driver for isolated power with
RS-485/PROFIBUS interfaces
Single 5V or 3.3V supply; low-current shutdown Simple open-loop circuit speeds powermode: 0.4µA; pin-selectable frequency of
supply design and shortens time to market
350kHz or 200kHz; µMAX package
MAX3107
SPI/I2C UART with integrated oscillators
24Mbps (max) data rate; 128B FIFOs; automatic
RS-485 transceiver control; 4 GPIOs; 24-pin
SSOP or small 3.5mm x 3.5mm TQFN packages
Tiny packages with integrated V L pin save
board space; V L pin communicates with
low-voltage FPGAs and microcontrollers
Serial interface and large FIFOs with
high integration reduce performance
requirements and cost of host controllers
For a list of Maxim's recommended PLC solutions, please go to: www.maxim-ic.com/plc.
50
Maxim Industrial Solutions
Programmable logic controllers (PLCs)
Recommended solutions
Recommended solutions (continued)
Digital I/O functions
Part
Description
Features
Benefits
Digital I/O modules
MAX14830*
Quad SPI/I2C UART with 128 byte FIFOs
24Mbps (max) data rate; integrated oscillator;
automatic transceiver control; 16 GPIOs;
7mm x 7mm, 48-pin TQFN package
Serial Interface reduces cost for isolators;
allows scalable architectures; simplifies
design; reduces overall cost
MAX14824*
IO-Link master transceiver
IO-Link master transceiver; a Type 1 and Type 2
digital input; addressable SPI interface
Addressable SPI reduces cost for isolation
in high-port-count masters
Power-line communications modems
MAX2990
10MHz to 490MHz OFDM-based power-line
communications modem
Combines the physical layer (PHY) and media
Removes wires by using the AC power line
access controller (MAC); 100kbps data rate over to transmit data
the power line
MAX2991
Integrated analog front-end (AFE) receiver
for power-line communications
For operation with MAX2990; integrates
on-chip band-select filter, VGA, and 10-bit ADC
for the Rx path; built-in 62dB dynamic-range
automatic gain control (AGC) and DC-offset
cancellation
Improves reliability and reduces system
cost by integrating the AFE for the
MAX2990; AGC and DC-offset cancellation
provide high-receiver sensitivity and added
reliability
MAX7030
Low-cost, factory-programmed ASK/OOK
transceiver
Low current; compact package; superior
sensitivity; no programming interface required
Extends battery life; smaller size; provides
longer range; facilitates faster and simpler
product design
MAX7031
Low-cost, factory-programmed FSK
transceiver
Low current; compact package; superior
sensitivity; no programming interface required
Extends battery life; smaller size; provides
longer range; facilitates faster and simpler
product design
MAX7032
Low-cost, frequency-programmable ASK/
FSK/OOK transceiver
Low current; compact package; superior
sensitivity; fully programmable 300MHz to
450MHz
Extends battery life; smaller size; provides
longer range and maximum flexibility
DS7505
Low-voltage, precision digital thermometer
and thermostat
±0.5°C accuracy from 0°C to +70°C; 1.7V to
3.7V operation; industry-standard pinout
Industry-standard pinout allows easy
accuracy upgrade and supply voltage
reduction from LM75
DS18B20
Precision 1-Wire digital temperature sensor
±0.5°C accuracy; 1-Wire interface; 64-bit,
factory-lasered ID code
Connects multiple precision temperature
sensors with less wire than any competitive
solution
MAX6631
Low-power, ±0.5°C accurate, digital
temperature sensor
±1°C accuracy from -0°C to +70°C; 50µA (max) Very low supply current for minimal impact
supply current
on system power usage
Battery-backup switchover ICs with
integrated regulated output
Low power; small TDFN package; integrated
regulated output
RF transceivers
Thermal management
Voltage supervisors
MAX16023/24
Conserve power
(Continued on next page)
*Future part—contact factory for availability.
www.digikey.com/maxim-industrial
51
Programmable logic controllers (PLCs)
Recommended solutions
Recommended solutions (continued)
Part
Description
Features
Benefits
MAX6381
Single-voltage supervisor
Multiple threshold and timeout options
Versatile for easy design reuse; saves space
in small modules
MAX6495
72V overvoltage protector
Protects against transients up to 72V; small,
6-pin TDFN-EP package
Increases system reliability by preventing
component damage due to high-voltage
transients; saves space; easy to use
MAX6720
Triple-voltage supervisor
Two fixed and one adjustable thresholds
Integrates three voltage monitors into one to
shrink design size
MAX6746
Capacitor-adjustable watchdog timer and
reset IC
Capacitor-adjustable timing; 3µA supply current Versatile for easy design reuse; saves space
in small modules
For a list of Maxim's recommended PLC solutions, please go to: www.maxim-ic.com/plc.
52
Maxim Industrial Solutions
Programmable logic controllers (PLCs)
Recommended solutions
Recommended solutions (continued)
CPU functions
Part
Description
Features
Benefits
Microcontrollers
MAXQ1850
32-bit secure microcontroller
256kB flash; 8kB, secure battery-backed SRAM; High security; tamper detection
DES/3DES, AES; 16MHz; SPI/USB interface
MAXQ1004*
1-Wire and SPI authentication 16-bit
microcontroller
1.7V to 3.6V supply range; 6MHz internal
oscillator; 10-bit ADC; SPI interface; AES;
random number generator (RNG); temp sensor
MAXQ2010
Low power 16-bit mixed-signal LCD
microcontroller
64kB flash; 8-channel, 12-bit SAR ADC;
High integration in a single chip; low power
160-segment LCD, hardware (HW) multiplier;
consumption
SPI/I2C and two USARTs interface; 370nA stopmode current
MAXQ8913
16-bit mixed-signal microcontroller
64kB flash; 7-channel, 12-bit SAR ADC; dual,
10-bit differential DACs; dual, 8-bit singleended DACs; four op amps; a temp sensor;
two current sinks; USART/SPI/I2C interface
High integration provides a true mixedsignal one-chip solution
MAXQ1103
32-bit secure microcontroller
External memory support; 512kB flash; 1kB,
secure battery-backed SRAM; DES/3DES;
25MHz
External code integrity check; tamper
detection
DS3600
Secure supervisor with 64B nonimprinting,
battery-backed encryption-key SRAM
Nonimprinting critical security-parameter
Improves system security by protecting
storage memory; SPI interface; external memory encryption keys from intruders
controller
DS3640
I2C secure supervisor with 1kB
nonimprinting, battery-backed encryptionkey SRAM
Nonimprinting memory; I2C interface; monitors
for external tampering; low power consumption
DS3644
1kB secure memory with programmable
tamper-detection hierarchy and RTC
Improves system security by protecting
Nonimprinting, critical security-parameter
encryption keys from intruders
storage memory; 10 different tamper inputs
(window comparator inputs, CMOS-level inputs,
fixed reference comparator inputs); configurable,
two-level hierarchical nonimprinting memory;
I2C interface; external memory controller
DS3645
Secure encryption-key controller with 4kB
of SRAM
10 different tamper inputs (window comparator
inputs, CMOS-level inputs, fixed reference
comparator inputs); I2C interface; external
memory controller
Improves system security by protecting
encryption keys from intruders
MAX36051B
Secure supervisor with 128B of secure
memory
Nonimprinting, critical security-parameter
storage memory; ultra-low < 3µW standby
power consumption; SPI interface
Improves system security by protecting
encryption keys from intruders
MAX16814
MAX16838
4-/2-channel high-brightness (HB) LED
drivers with integrated DC-DC controller
150mA/channel capability; 4.75V to 40V input
voltage; adaptive boost control
Fit in small board area and lowers BOM
cost
MAX16826
Programmable, 4-channel HB LED driver
with integrated DC-DC controller
4.75V to 24V input voltage; up to > 300mA/
channel current capability; I2C interface
Easily controllable from a microcontroller
MAX16809
16-channel LED driver with integrated
DC-DC controller
8V to 26.5V input voltage; 55mA/channel
current capability
Reduces BOM complexity
Low-power data/code authentication
Secure supervisors
Improves system security by protecting
encryption keys from intruders
LED backlighting
(Continued on next page)
*Future part—contact factory for availability.
www.digikey.com/maxim-industrial
53
Programmable logic controllers (PLCs)
Recommended solutions
Recommended solutions (continued)
Part
Description
Features
Benefits
LED backlighting (continued)
MAX8790A
6-channel white-LED (WLED) driver for LCD 4.5V to 26V input voltage; 15mA to 25mA (adj),
panel applications
full-scale LED current; adaptive boost control
Compact design
DS7505
Low-voltage, precision digital thermometer
and thermostat
±0.5°C accuracy from 0°C to +70°C; 1.7V to
3.7V operation; industry-standard pinout
Industry-standard pinout allows easy
accuracy upgrade and supply voltage
reduction from LM75
DS18B20
Precision 1-Wire digital temperature sensor
±0.5°C accuracy; 1-Wire interface; 64-bit,
factory-lasered ID code
Connects multiple precision temperature
sensors with less wire than any competitive
solution
MAX6602
5-channel precision temperature monitor
One local and four remote digital sensing
channels; ±1°C accuracy
Reduces board space compared to five
separate temperature sensors
MAX11800
Resistive touch-screen controller
FIFO; spatial filtering; SPI interface
Offloads host processor to perform other
functions
MAX11801
Resistive touch-screen controller
FIFO; spatial filtering; I2C interface
Offloads host processor to perform other
functions
MAX11802
Resistive touch-screen controller with SPI
interface
SPI interface
Reduces cost
MAX11803
Resistive touch-screen controller with I2C
interface
I2C interface
Reduces cost
MAX11811
Resistive touch-screen controller with
haptics driver
Integrated haptics driver; I2C interface
Conveniently adds touch feedback to
resistive touch screens
MAX16023/24
Battery-backup switchover ICs with
integrated regulated output
Low power; small TDFN package; integrated
regulated output
Conserve power
MAX6381
Single-voltage supervisor
Multiple threshold and timeout options
Versatile for easy design reuse; saves space
in small modules
MAX6495
72V overvoltage protector
Protection against transients up to 72V; small,
6-pin TDFN-EP package
Increases system reliability by preventing
component damage due to high-voltage
transients; saves space; easy to use
MAX6720
Triple-voltage supervisor
Two fixed and one adjustable thresholds
Integrates three voltage monitors to shrink
design size
MAX6746
Capacitor-adjustable watchdog timer and
reset IC
Capacitor-adjustable timing; 3µA supply current Versatile for easy design reuse; saves space
in small modules
Thermal management
Touch-screen controllers
Voltage supervisors
For a list of Maxim's recommended PLC solutions, please go to: www.maxim-ic.com/plc.
54
Maxim Industrial Solutions
Programmable logic controllers (PLCs)
Recommended solutions
Recommended solutions (continued)
Isolated power-supply functions
Part
Description
Features
Benefits
DC-DC converters and controllers
MAX5080/81
Step-down DC-DC converters with
integrated switch
4.5V/7.5V to 40V V IN; 1.23V to 32V VOUT; switch Save cost with integrated DC-DC
to pulse-skip mode at light loads; integrated
converters that power directly off an
high-side switch
industrial bus
MAX5072
Dual-output buck or boost converter with
integrated switch
4.5V to 5.5V or 5.5V to 23V V IN; 0.8V (buck) to Improves reliability with controlled inrush
28V (boost) VOUT; configure each output as buck current, thermal shutdown, short-circuit
or boost
protection
MAX15023
Wide 4.5V to 28V input, dual-output
synchronous buck controller
4.5V to 28V V IN; VOUT = 0.6V to 0.85 × V IN;
hiccup mode
Thermal shutdown and short-circuitprotection protect system
MAX15034
Single-/dual-output synchronous buck
controller for high-current applications
4.75V to 5.5V or 5V to 28V V IN; VOUT = 0.61V to
5.5V; 25A or 50A output
Thermal shutdown and monotonic start
protect devices, improve reliability
MAX15048/49
3-channel DC-DC controllers with tracking/
sequencing
4.7V to 23V V IN; VOUT = 0.6V to 19V; tracking
across the three outputs; power sequencing
Save space and costs by integrating three
switching controllers
Isolated power-supply controllers and converters
MAX5094/95
High-performance single-ended, currentmode PWM controllers
Adjustable frequency; high-voltage startup;
internal error amplifier; thermal shutdown
Enhance reliable operation of highperformance PLCs with short 60ns delay
from current sense to output
MAX5042
Two-switch, voltage-mode PWM power IC
with integrated power MOSFETs and hotswap controller
Adjustable frequency; high-voltage startup; internal error amplifier; synchronizable
frequencies; synchronous rectifier driver
Integrated hot-swap controller and
MOSFETs cut costs and connect directly to
48V bus; simplifies board design
MAX5070
Single-ended current-mode PWM controller
Adjustable frequency; high-voltage startup;
internal error amplifier
Enhances reliable operation with less than
half the delay of competing solutions from
current sense to output
MAX5069
High-frequency current-mode PWM
controller with accurate oscillator and dual
FET drivers
Adjustable frequency; high-voltage startup;
internal error amplifier; synchronizable
frequencies
Lowers BOM costs using a smaller inductor
and output filter capacitor for 100W
applications
MAX5014
Current-mode PWM controller with
integrated start up circuit
High-voltage startup
Lowers BOM cost and simplifies design;
eliminates the need for external startup
components for 75W applications
MAX256
3W primary-side transformer H-bridge driver Isolated power supply up to 3W
for isolated supplies
Simple open-loop circuit speeds powersupply design; reduces time to market
MAX5079
OR-ing MOSFET controller
Ultra-fast 200ns turn-off
Reduces cost/size/power in high-power
applications by replacing Schottky diodes
MAX5075
Push-pull FET driver with clock output and
integrated oscillator
Adjustable frequency; synchronizable
frequencies; undervoltage lockout (UVLO)
Lowers overall system cost of unregulated
isolated power supplies/modules that drive
PLCs
MAX5059
Parallelable, secondary-side synchronous
rectifier driver and feedback-generator
controller IC
Internal error amplifier; synchronizable
frequencies; synchronous rectifier driver;
thermal shutdown; UVLO
Simplifies design; lowers BOM costs with
integrated digital-output margining circuit
MAX15024/25
FET drivers
Single/dual operation; 16ns; high sink/source
current
Simplify design with a very low propagation
delay and a thermally enhanced package
MAX5048
MAX5054/55/56/57
MAX5078
FET drivers
4A to 7.6A; 12ns to 20ns; single/dual MOSFET
drivers
Increase flexibility for modular PLC
supplies with inverting/noninverting inputs
to control the MOSFET
MOSFET/rectifier drivers
(Continued on next page)
www.digikey.com/maxim-industrial
55
Programmable logic controllers (PLCs)
Recommended solutions
Recommended solutions (continued)
Part
Description
Features
Benefits
Thermal management
DS7505
Low-voltage, precision digital thermometer
and thermostat
±0.5°C accuracy from 0°C to +70°C; 1.7V to
3.7V operation; industry-standard pinout
Industry-standard pinout allows easy
accuracy upgrade and supply voltage
reduction from LM75
MAX6602
5-channel precision temperature monitor
Local and four remote digital sensing channels;
±1°C accuracy
Reduces board space compared to five
separate temperature sensors
MAX6509
Resistor-programmable temperature
switches
Resistor-programmable trip temperature; 6-pin
SOT23 package
Simple protection against damage from
overtemperature events
MAX6639
2-channel temperature monitor and PWM
fan controller
Internal and external temperature measurement; Closed-loop control over fan speed
closed-loop RPM control
minimizes noise and power
MAX16023/24
Battery-backup switchover ICs with
integrated regulated output
Low power; small TDFN package; integrated
regulated output
Conserve power
MAX6381
Single-voltage supervisor
Multiple threshold and timeout options
Versatile for easy design reuse; saves space
in small modules
MAX6495
72V overvoltage protector
Protection against transients up to 72V; small,
6-pin TDFN-EP package
Increases system reliability by preventing
component damage due to high-voltage
transients; saves space; easy to use
MAX6720
Triple-voltage supervisor
Two fixed and one adjustable thresholds
Integrates three voltage monitors to shrink
design size
MAX6746
Capacitor-adjustable watchdog timer and
reset IC
Capacitor-adjustable timing; 3µA supply current Versatile for easy design reuse; saves space
in small modules
Voltage supervisors
For a list of Maxim's recommended PLC solutions, please go to: www.maxim-ic.com/plc.
56
Maxim Industrial Solutions
Sensors
Sensors
Overview
Overview
Industrial processes use sensors
to monitor physical properties.
Examples include temperature in
a furnace, pressure in a chamber,
environmental humidity, gas or
liquid flows through pipes, weights
of ingredients, and current flow in
motor windings.
an electrical signal. Some transducers are resistive elements that
require external excitation to create
a measurable voltage. Other transducers generate their own voltages
or currents in response to physical
properties such as light, temperature,
or sound.
A complete sensor assembly
includes: a transducer (commonly
called a sensor); signal conditioning
and communications circuitry; a housing; and a connector. The
transducer converts physical properties such as weight, pressure,
temperature, humidity, or light to
The signals coming from transducers are usually very small and
require optimized interface circuits
to provide adequate gains without
introducing noise that reduces
accuracy. Sensor assemblies are
often located far from the digital
processing circuitry, so EMI protec-
TRANSDUCER /
BRIDGE
AFE
FILTER
ADC
tion, isolation, and low power are
often required. Besides the signal
chain, there are sometimes stringent
requirements for power management, communication (among
devices/systems), and secure data
transmission.
Maxim provides ICs that address all
aspects of the sensor signal chain,
from conditioning to capture, transmission to timing, and power to
precision. With Maxim, you will most
likely find the right solution for your
sensor application.
DIGITAL DOMAIN
COMMUNICATIONS
INTEGRATED SIGNAL CONDITIONER
Ve
R
–
–
–
+
+
+
REFERENCE
TOUCH
SCREEN
CompoNet®
R-∆R
HART®
ADC
R+∆R
R
μC
IO-LINK®
DIGITAL IO
OP AMPS
PRECISION
RESISTORS
PGA
TEMP
SENSORS
IA
PRECISION
RESISTORS
DIGITAL
POTENTIOMETERS
RS-485
FILTERS
= MAXIM SOLUTION
OP AMPS
REF
POWER
DAC
SUPERVISORS
TIMING
DAC
MISCELLANEOUS
EXCITATION
FEEDBACK
Block diagram of a basic sensor system for industrial processes. For a list of Maxim’s recommended sensor solutions, please go to: www.maxim-ic.com/sensor.
www.maxim-ic.com/sensor
www.digikey.com/maxim-industrial
59
Sensors
Pressure sensors and weigh scales (force sensing)
Pressure sensors and weigh scales (force sensing)
Overview
The two most common types of
strain gauges are the metal-foil type
used in a variety of weight/pressure
sensors and the semiconductorbased piezoresistive transducers,
widely used to measure pressure.
Compared to metal-foil-type transducers, piezoresistive transducers are
more sensitive with better linearity,
but have large temperature dependence and large initial offsets.
The need to detect and measure
pressure and weight is a very
common requirement for modern
industrial control and system monitoring. Pressure measurement is
especially important, as it is also used
indirectly to measure flow, altitude,
and other properties. Pressure- and
weight-measurement devices can
be regarded as “force sensors,” since
force is the property that affects the
transducers’ outputs. The applications for force sensors are vast and
range from vacuum gauges, to heavy
machinery weigh scales, industrial
hydraulic equipment, and manifold
absolute pressure (MAP) sensors for
internal-combustion engines. Each
application has its own diverse needs
for precision, accuracy, and cost. TRANSDUCER /
BRIDGE
Although there are several methods
and technologies for measuring
pressure and weight (force sensing),
the most commonly used measurement element is the strain gauge.
AFE
FILTER
In principle, all strain gauges react to an applied force by varying a
resistance value. Therefore, in the
presence of electrical excitation they
effectively convert a pressure or
weight to an electrical signal. Usually,
one, two, or four of these active
resistive elements (strain gauges)
are arranged in a Wheatstone bridge
configuration (sometimes called a
ADC
DIGITAL DOMAIN
INTEGRATED SIGNAL CONDITIONER
μC
ADC
ADC
OP AMPS
PGA
TEMP
SENSORS
PRECISION
RESISTORS
DIGITAL
POTENTIOMETERS
LEVEL
TRANSLATOR
REFERENCE
Reference
FILTERS
ISOLATION
IA
OP AMPS
DAC
REF
= MAXIM SOLUTION
EXCITATION
Block diagram of the signal chain in a force-sense application. For a list of Maxim’s recommended pressure-sensor solutions, please go to: www.maxim-ic.com/psi.
60
Maxim Industrial Solutions
Sensors
Pressure sensors and weigh scales (force sensing)
load cell) to produce a differential
output voltage in response to
pressure or weight.
Engineers can design a sensor module
that meets the unique requirements
of diverse force-sensing applications.
A successful design will include the
suitable sensing element for the
physical property and an appropriately designed signal chain.
Complete signal-chain
solutions
The sensor signal chain must handle extremely small signals in the presence of noise. Accurately
measuring changes in the output
voltage from a resistive transducer
requires circuitry that provides the
following electrical functions with
precision: excitation, amplification,
filtering, and acquisition. Some
solutions may also require the use of
digital-signal processing (DSP) techniques for signal manipulation,
error compensation, digital gain, and user programmability.
Excitation
Accurate and stable voltage or current
sources with low-temperature drift
are generally used for sensor excitation. The sensor output is ratiometric
(usually expressed in mV/V) to the
excitation source. Consequently,
the design typically has a common
reference for both the analog-todigital converter (ADC) and the
excitation circuitry, or it uses the excitation voltage as the reference
for the ADC. Additional ADC channels
can be used to measure the excitation voltage accurately.
Transducer/bridge
This part of the signal chain consists
of the strain-gauge transducers
arranged in a load cell (Wheatstone
bridge format), as briefly explained in
the overview section above.
www.digikey.com/maxim-industrial
Amplification and level translation—the analog front-end (AFE)
In some designs the transducer’s
output-voltage range will be very
small, with the required resolution
reaching the nano-volt range. In
such cases, the transducer’s output
signal must be amplified before it
is applied to the ADC’s inputs. To
prevent this amplification step from
introducing errors, low-noise amplifiers (LNAs) with extremely low offset
voltage (VOS) and low-temperature
and offset drifts must be selected.
A drawback of Wheatstone bridges
is that the common-mode voltage
is much larger than the signal of
interest. This means that the LNAs
must also have excellent commonmode rejection ratios (CMRRs),
generally greater than 100dB. When
single-ended ADCs are used, additional circuitry is required to remove
large common-mode voltages before
acquisition. Additionally, since the
signal bandwidth is low, the 1/f noise
of the amplifiers can introduce errors.
Chopper-stabilized amplifiers are,
therefore, often used. Some of these
stringent amplifier requirements can
be avoided by using a small portion
of the full-scale range of a very-highresolution ADC. Acquisition—the ADC
When choosing the ADC, look
at specifications like noise-free
range or effective resolution
which indicate how well an ADC
can distinguish a fixed input level.
Alternate terms might be noise-
free counts or codes inside the
range. Most high-accuracy ADC
data sheets show these specifications as a table of peak-to-peak
noise or RMS noise versus speed;
sometimes the specifications
are shown graphically as noise
histogram plots.
Other ADC considerations include
low-offset error, low-temperature
drift, and good linearity. For certain
low-power applications, speed
versus power is another important
criterion.
Filtering
The bandwidth of the transducer
signal is generally small and the
sensitivity to noise is high. It is,
therefore, useful to limit the signal
bandwidth by filtering to reduce
the total noise. Using a sigma-delta
ADC can simplify the noise-filtering
requirement because of the inherent
oversampling in that architecture
Digital Signal Processing (DSP)—
the digital domain
Besides the analog signal processing,
the captured signals are further
processed in the digital domain
for signal extraction and noise
reduction. It is common to find
focused algorithms that cater to
particular applications and their
nuances. There are also generic
techniques, such as offset and gain
correction, linearization, digital
filtering, and temperature- (and other dependent factors) based
compensation that are usually
applied in the digital domain.
Signal conditioning/
integrated solutions
In some integrated solutions, all
required functional blocks are integrated into a single IC commonly
called a sensor signal conditioner. A
signal conditioner is an applicationspecific IC (ASIC) that performs
compensation, amplification, and
calibration of the input signal,
normally over a range of temperatures. Depending on the sophistica-
tion of the signal conditioner, the
ASIC integrates some or all of the
following blocks: sensor excitation
circuitry, digital-to-analog converter
(DAC), programmable gain amplifier
(PGA), analog-to-digital converter
(ADC), memory, multiplexer (MUX),
61
Sensors
Pressure sensors and weigh scales (force sensing)
CPU, temperature sensor, and digital interface.
Two types of signal conditioners are
commonly used: analog signal-path
conditioner (analog conditioner)
and digital signal-path conditioner
(digital conditioner). Analog condi-
tioners have a faster response time
and provide a continuous-output
signal, reflecting changes on the
input signal. They generally have a
hardwired (inflexible) compensation
scheme. Digital conditioners, which
are usually microcontroller based,
have slower response times because
of latencies introduced by the ADC
and DSP routines. The ADC resolution should be reviewed to minimize
quantization errors. The biggest
benefit of digital signal conditioners
is the flexibility of the compensation
algorithms which can be adapted to
the user’s application.
www.maxim-ic.com/psi
62
Maxim Industrial Solutions
Sensors
Pressure sensors and weigh scales (force sensing)
Flexible ADCs interface with a wide range of sensors
MAX1415/MAX1416, MX7705
Benefits
Pressure sensors commonly have high temperature dependence.
Therefore, the design should monitor temperature while measuring
pressure. The MAX1415 features differential reference inputs which
allow ratiometric measurement of the 3V excitation voltage. The two
differential inputs allow pressure and temperature (using a resistance
temperature detector, RTD) to be monitored with a single ADC.
•• Distinguish signals better by matching
sensor’s output range to the ADC’s
input range
–– On-chip PGA allows as low as 20mV
full-scale range (FSR) to match sensor
output
•• High integration reduces design
complexity
–– Built-in self- and system-calibration
modes improve accuracy and shorten
design time
–– Built-in digital filter for 50Hz/60Hz
rejection removes unwanted power-line
interference
•• Simplify design with features
optimized for multichannel ratiometric/
bridge-type designs
–– Differential reference input for
ratiometric measurement common to
bridge-type circuits
–– Two differential channels measure
pressure and temperature (common
dependency)
V3
AIN1+
VS1
NPI-19 SERIES
NovaSensor®
PRESSURE SENSOR
MAX1415
AIN1−
SPI™
INTERFACE
AIN2+
VS2
AIN2−
REF+
REF−
HEL 777
RTD
R1
Flexible MAX1415 ADC interfaces with pressure and temperature sensors.
www.digikey.com/maxim-industrial
63
Sensors
Pressure sensors and weigh scales (force sensing)
Maintain high accuracy over time and temperature
MAX9617/MAX9618, MAX11200*
Benefits
One of the biggest challenges with interfacing to sensors is the
low signal levels. Since the signal bandwidth (BW) lies in low hertz
for many sensors, the 1/f noise of op amps is an important factor.
Maxim’s MAX9617/MAX9618 low-power (< 100µA) op amps offer the
industry’s lowest noise, autozero (42nV/√Hz) operation. These devices
have the best-in-class peak-to-peak noise of < 420nVP-P for 0.1Hz to
10Hz BW. Coupled with the MAX11200, industry’s leading low-power,
24-bit (21 noise-free bits) resolution, sigma-delta ADC, these op amps
form an ideal circuit for capturing low-frequency, low-amplitude
signals accurately.
•• Minimize system calibration over time
and temperature (MAX9617/MAX9618)
–– Autozero op-amp technology reduces
TCVOS to 120nV/°C
•• Provides the most accurate measurements at the lowest power (MAX11200*)
–– Highest resolution per-unit-power ADC
for sensors on a 4–20mA loop: 21 bits of
noise-free range at 10sps drawing close
to 200µA
–– Lowest < 780µW noise density for lowfrequency design
•• Distinguishes extremely small changes
over a wide range of pressure or weight
(MAX11200)
–– 21 bits of noise-free range identify
signals down to 500nV steps for
wide-range, high-accuracy sensor
applications
–– Industry’s lowest noise, autozero op amp
operation with < 420nVP-P noise from
0.1Hz to 10Hz
–– No 1/f component ensures low
distortion below 0.1Hz in the signal-
conditioning stage
CURRENT
REFERENCE
−
REF+
X 100
REF−
AIN+
+
AIN−
MAX11200*
MAX9617/
MAX9618
Circuit using the MAX9617/MAX9618 op amps and the MAX11200 ADC achieves high accuracy over time and temperature.
*Future product—contact factory for availability.
64
Maxim Industrial Solutions
Sensors
Pressure sensors and weigh scales (force sensing)
Low-cost, high-precision sensor signal conditioner simplifies sensor design
MAX1452
Benefits
The MAX1452 is a versatile analog sensor signal conditioner that
accepts output from all types of resistive elements. Its fully analog
signal path enables a fast response and also provides current or
voltage excitation for optimal design flexibility. Four integrated
16-bit DACs and a PGA provide high-resolution input compensation,
amplification, and calibration. The MAX1452 includes on-chip flash
memory and a temperature sensor that performs multitemperaturepoint compensation for accurate readings.
•• Reduces Bill of Materials (BOM) cost
–– High integration minimizes external
components, requires no external trim
components; to produce calibrated and
accurate output
•• Removes all systematic errors for a
highly accurate output
–– Fully analog signal path provides a
continuous output with no quantization
error
–– Four 16-bit DACs (76μV resolution)
provide compensation accuracy of
full-span output (FSO) and offset
–– Multitemperature compensation allows
calibration that approaches repeatability
of the input signal
•• Reduces product development time and
inventory complexity
–– Suitable for use with many types of
transducers and in multiple applications
–– Using same signal conditioner in
many applications allows reuse of the
application circuit –– Can be used in products requiring
voltage output or 4–20mA current loop
5V
30Ω
VDD
BDR
VDDF
INP
MAX1452
SENSOR
OUT
OUT
INM
1µF
0.1µF
0.1µF
VSS
GND
Low-cost and high-precision MAX1452 sensor signal conditioner in a ratiometric configuration.
www.digikey.com/maxim-industrial
65
Sensors
Pressure sensors and weigh scales (force sensing)
Low-power, low-noise, multichannel sensor signal processor saves cost and
board space
MAX1464
Benefits
The MAX1464 is a highly integrated, digital, multichannel sensor signal
conditioner optimized for industrial process-control and automotive
applications. Typical implementations include pressure sensing, RTD
and thermocouple linearization, weight sensing/classification, and
remote process monitoring with limit indication. The MAX1464
simplifies designs and improves manufacturing efficiency by accepting
sensors with either single-ended or differential outputs. It provides
comprehensive temperature compensation without requiring any
external trim components. A calibrated output signal can be driven
independently through an SPI-compatible interface, voltage-output
DACs, or PWM terminals. The MAX1464 integrates a 16-bit CPU; 4kB of
flash memory for a user-programmable compensation algorithm and
128 bytes for user information; and two general-purpose inputs/
outputs (GPIOs). It has a flexible dual op-amp output block and
supports 4–20mA applications.
•• Saves cost and board space by
interfacing directly with a microprocessor or control unit
–– SPI-compatible interface eliminates
need for interface stage
–– GPIO terminals facilitate instrument
control, system warning, and two-way
signaling
•• Multichannel functionality reduces
BOM cost, improves performance, and
saves space
–– Use one multichannel device instead of
multiple devices , so measurements are
more comparable and costs lowered
–– Highly integrated conditioner minimizes
component requirements and saves
board space
–– No external trim components required
for a calibrated and accurate output
•• Adaptable compensation algorithm
optimizes sensor performance
–– User can customize the compensation
algorithm suitable for the application
–– Compensation algorithm is stored in
on-chip nonvolatile (NV) flash memory
•• Reduces product development time
–– Flexible for use in products requiring
digital output, voltage output, PWM
output, or a 4–20mA current loop
–– Integrated microprocessor with only 16
instructions makes programming easy
–– Suitable for use with many types of
transducers
(Block diagram on next page)
66
Maxim Industrial Solutions
Sensors
Pressure sensors and weigh scales (force sensing)
Low-power, low-noise, multichannel sensor signal processor saves cost and
board space (continued)
5V
22Ω
VDD
INP1
VDDF
RREF
SENSOR
INM1
MAX1464
INP2
OUTNSM
OUT, BRIDGE
OUTNLG
OUT, RTD
GPION
SYSTEM
CONTROL UNIT
DIGITAL INTERFACE
INM2
RTD
VSS
RT*
0.1μf
0.1μf
100pf
100pf
GND
* RT is a resistor with a negligible tempco (TC) or a well-known TC .
The MAX1464 multichannel digital signal conditioner measures one differential and two single-ended inputs.
www.digikey.com/maxim-industrial
67
Sensors
Temperature sensing
Temperature sensing
Overview
Thermistors, RTDs, thermocouples,
and ICs are some of today’s most
widely used temperature-sensing
technologies. Each design approach
has its own strengths (e.g., cost,
accuracy, temperature range) which
make it appropriate for specific applications. Each of these technologies
will be discussed below.
Temperature sensing is critically
important for implementing three
key functions in industrial systems.
1. Temperature control, for
example in ovens, refrigeration,
and environmental-control
systems, depends on the
measurement of temperature to
make heating/cooling decisions.
3. Protection of components and
systems from damaging temperature excursions. Temperature
sensing determines the appropriate action to take.
2. Calibration of a variety of
transducers, oscillators, and
other components often varies
with temperature. Therefore,
temperature must be measured
to ensure the accuracy of sensitive
system components.
SENSOR AND
NETWORK
AFE
FILTER
In addition to the industry’s most
comprehensive line of dedicated
temperature-sensor ICs, Maxim
manufactures all of the components necessary to interface a
system to thermistors, RTDs, and
thermocouples.
ADC
DIGITAL DOMAIN
THERMOCOUPLE
μC
V
ADC
ADC
RTD
OP AMPS
PRECISION
RESISTORS
DIGITAL
POTENTIOMETERS
LEVEL
TRANSLATOR
TOUCH
SCREEN
REFERENCE
Reference
PGA
ISOLATION
THERMISTOR
IA
TEMP
SENSORS
REF
DAC
= MAXIM SOLUTION
EXCITATION
Block diagram of the signal chain in a temperature-sensing application. For a list of Maxim’s recommended temperature-sensor solutions, please go to: www.maxim-ic.com/-40+85.
68
Maxim Industrial Solutions
Sensors
Temperature sensing
Thermistors
Thermistors are temperaturedependent resistors, usually made
from semiconducting materials like
metal-oxide ceramics or polymers.
The most widely used thermistors
have a negative temperature co-
efficient of resistance and, therefore,
are often referred to as NTCs. There are also positive temperature co-
efficient (PTC) thermistors.
Thermistor characteristics include
a moderate temperature range
generally up to +150°C, although
some are capable of much higher
temperatures; low-to-moderate cost
depending on accuracy; and poor,
but predictable linearity. Thermistors
are available in probes, in surfacemount packages, with bare leads,
and in a variety of specialized
packages. Maxim also manufactures
ICs like the MAX6682 and MAX6698
that convert thermistor resistance to
a digital format. A thermistor is often connected to
one or more fixed-value resistors to
create a voltage-divider. The output
of the divider is typically digitized by
an ADC. The thermistor’s nonlinearity
can be corrected either by a lookup
table or by calculation.
with a precision, fixed resistor to
create a voltage-divider, or it can be
more complex, especially for widerange temperature measurements.
A common approach consists of a
precision current source, a voltage
reference, and a high-resolution ADC,
as shown in Figure 1. Linearization
can be performed with a lookup
table, calculation, or external linear
circuits.
Thermocouples
Thermocouples are made by joining
two wires of dissimilar metals. The
point of contact between the wires
generates a voltage that is approximately proportional to temperature.
There are several thermocouple
types which are designated by
letters. The most popular is the K type.
Thermocouple characteristics
include a wide temperature range
up to +1800°C; low cost, depending
RTD characteristics include a wide
temperature range up to +750°C,
excellent accuracy and repeatability,
and reasonable linearity. For Pt-RTDs,
the most common values for nominal
resistance at 0°C are 100Ω and 1kΩ,
although other values are available. Signal conditioning for an RTD can
be as simple as combining the RTD
www.digikey.com/maxim-industrial
Measuring temperature with a thermocouple is somewhat difficult
because the thermocouple’s output
is low. Measurement is further
complicated because additional
thermocouples are created at the
point where the thermocouple
wires contact the copper wires (or
traces) that connect to the signalconditioning circuitry. This contact
point is called the cold junction (see
Figure 2). To accurately measure
temperature with a thermocouple, a
second temperature sensor must be
added at the cold junction, as shown
in Figure 3. Then the temperature
measured at the cold junction is
added to the value indicated by the
measurement of the thermocouple
VOLTAGE
REFERENCE
PRECISION
CURRENT
SOURCE
INPUT
RTDs
Resistance temperature detectors
(RTDs) are resistors whose resistance
varies with temperature. Platinum
is the most common, most accurate
wire material; platinum RTDs are
referred to as Pt-RTDs. Nickel, copper,
and other metals can also be used to
make RTDs.
on package; very-low-output
voltage of about 40µV per °C for a
K-type device; reasonable linearity;
and moderately complex signal
conditioning, i.e., cold-junction
compensation and amplification.
ADC
(12 BITS TO 16 BITS)
TO MICROCONTROLLER
RTD
Figure 1. Simplified RTD signal-conditioning circuit.
COLD JUNCTION
THERMOCOUPLE
METAL 1
COPPER
WIRE
VOUT
METAL 2
COPPER
WIRE
Figure 2. Simple thermocouple circuit. The junction between metal 1 and metal 2 is the main
thermocouple junction. Other thermocouples are present where the metal 1 and metal 2 wires join
with the measuring device’s copper wires or PC-board (PCB) traces.
69
Sensors
Temperature sensing
voltage. The example circuit in Figure
3 shows one implementation, which
includes a number of precision
components.
In addition to all of the components shown in Figure 3, Maxim
manufactures the MAX6674 and
MAX6675 which perform the
signal-conditioning functions
for K-type thermocouples. These
devices simplify the design task and
significantly reduce the number of
components required to amplify,
cold-junction compensate, and
digitize the thermocouple’s output.
Temperature-sensor ICs
Temperature-sensor ICs take
advantage of the linear and predictable thermal characteristics of silicon
PN junctions. Because they are
active circuits built using conventional semiconductor processes,
these ICs take a variety of forms.
They include many features such as
digital interfaces, ADC inputs, and
fan-control functions that are not
available in other technologies. The
operating temperature range for
temperature-sensor ICs extends as
low as -55°C and as high as +125°C,
with a few products operating to
an upper limit of around +150°C.
Descriptions of common types of
temperature-sensor ICs follow.
Analog temperature sensors
Analog temperature-sensor ICs
convert temperature to voltage
or, in some cases, to current. The
simplest voltage-output analog
temperature sensors have just three
active connections: ground, powersupply voltage input, and output.
Other analog sensors with enhanced
features have additional inputs or
outputs, for example, comparator or
voltage-reference outputs.
Analog temperature sensors use the
thermal characteristics of bipolar
transistors to develop an output
voltage that is proportional to
temperature. Gain and offset are
applied to this voltage to provide a
convenient relationship between the
sensor’s output voltage and the die
temperature. Temperature accuracy
can be excellent. The DS600, for
example, is the industry’s most
accurate analog temperature sensor,
with guaranteed error less than
±0.5°C from -20°C to +100°C.
Local digital temperature sensors
Integrating an analog temperature
sensor with an ADC is an obvious
way to create a temperature sensor
with a direct digital interface. Such
a device is normally called a digital
temperature sensor or a local
digital temperature sensor. “Local”
THERMOCOUPLE
indicates that the sensor measures
its own temperature. This operation
contrasts with a remote sensor that
measures the temperature of an
external IC or a discrete transistor.
Basic digital temperature sensors
simply measure temperature
and allow the temperature data
to be read by a number of interfaces including 1-Wire®, I2C, PWM,
and 3-wire. More complex digital
sensors offer other features, such as
over-/undertemperature outputs,
registers to set trip thresholds for
these outputs, and EEPROM. Maxim
manufactures several local digital
temperature sensors, including the
DS7505 and DS18B20 that guarantee
accuracy of ±0.5°C over a wide
temperature range.
Remote digital temperature
sensors
A remote digital temperature sensor
is also called a remote sensor or a
thermal diode sensor. The remote
sensor measures the temperature
of an external transistor, either a
discrete transistor or one that is integrated on the die of another IC, as
shown in Figure 4. Microprocessors,
field-programmable gate arrays
(FPGAs), and ASICs often include one
or more sensing transistors, usually
called thermal diodes, similar to the
one shown in Figure 4.
VOLTAGE
REFERENCE
PRECISION
AMPLIFIER
TEMPERATURE
SENSOR
IN1
IN2
ADC
(12 BITS TO 24 BITS)
TO
MICROCONTROLLER
PRECISION RESISTORS
Figure 3. Example of a thermocouple signal-conditioning circuit.
70
Maxim Industrial Solutions
Sensors
Temperature sensing
There is an important advantage to
remote temperature sensors: they
allow you to monitor more than
one hot spot with a single IC. A
basic single remote sensor like the
MAX6642 in Figure 4 can monitor
two temperatures: its own and an
external temperature. The external
location can be on the die of a target
IC, as in Figure 4, or a hot spot on a
board that it monitors with a discrete
transistor. Some remote sensors
monitor as many as seven external
temperatures. Thus, eight locations,
consisting of ICs and board hot
spots, are monitored from a single
chip. Consider the MAX6602 as an
example. This temperature sensor
has four remote diode inputs so
it can monitor the temperatures
of a pair of FPGAs with integrated
thermal diodes, two board hot
spots using discrete transistors,
and the temperature of the board
at the MAX6602’s location. Both
the MAX6602 and the MAX6642
mentioned here achieve ±1°C
accuracy when reading external
thermal diodes.
+3.3V
VCC
CPU, ASIC,
FPGA
4.7kΩ
MAX6642
DXP
SMBCLK
2200pF
ON-CHIP
PN JUNCTION
SMBDATA
ALERT
SMBus™/I2C SERIAL
INTERFACE
INTERFACE
(TO MASTER)
GND
Figure 4. A remote temperature sensor, the MAX6642, monitors the temperature of a sensing transistor (or thermal diode) on
the die of an external IC.
www.maxim-ic.com/-40+85
www.digikey.com/maxim-industrial
71
Sensors
Temperature sensing
Simple, integrated RTD-to-digital conversion
MAX1402, MAX4236/
MAX4237
Any appreciable resistance in the RTD’s
leads will cause errors in temperature
measurement. Therefore, for long wire
lengths use a 3- or 4-wire connection
to eliminate lead-resistance errors. The
circuit in Figure A is a 4-wire RTD
interface using the MAX1402 oversampling ADC. The MAX1402 has two
matched current sources, which significantly reduce the IC count in an RTD
converter. One of the current sources
provides excitation current for the RTD,
in this case, a Pt100. Because the
excitation current does not flow
through the sense leads, lead resistance
will not affect the temperaturemeasurement accuracy. The second
current source drives a precision resistor
to generate the reference voltage for
the ADC, thereby eliminating the need
for an external voltage reference.
For best accuracy when using an
RTD, apply linearity correction to the
acquired data to compensate for the
Pt100’s nonlinearity. Also use gain
correction to compensate for both the
tolerance of the reference resistor and
mismatch between the current sources.
The digital linearity correction can be
avoided if a small amount of positive
feedback is applied to an amplifier
circuit, as shown in Figure B. The
resulting linearity error from -100°C to
+200°C is less than ±0.05°C. This circuit
does not compensate for long leads,
so it should be used when the RTD is
located near the measurement circuitry.
For more details, refer to Maxim’s
application note 3450, “Positive
Analog Feedback Compensates Pt100 Transducer.”
5V
V+
VDD
R5
3.01kΩ
200µA
OUT2
MAX1402
REFIN+
R2
11.8kΩ
MODULATOR
RREF
REFIN200µA
+
V1
R1
11kΩ
OUT1
5V
MAX4236
MAX4237A
VOUT
−
AIN1
R3
105kΩ
RTD
Pt100
100Ω
PGA
AIN2
R4
12.4kΩ
A = 1 TO 128
AGND
DGND
Figure A. Circuit diagram shows the MAX1402 ADC in a 4-wire
interface for a Pt100 RTD.
72
Figure B. A Pt100 linearizer circuit. Pt100 is compensated by one additional resistor. R2 provides
a small positive feedback.
Maxim Industrial Solutions
Sensors
Temperature sensing
Complete thermocouple interface designs eliminate external components,
use less space
DS600, MAX1416, MAX6133,
MAX6675
common-mode range extends 30mV below ground.
The thermocouple circuit shown in
Figure A uses the MAX1416 ADC
that allows direct interfacing with
thermocouples, thereby eliminating
external components and reducing
the overall footprint. The internal
programmable gain amplifier (PGA)
eliminates the need for an external
precision amplifier; self-calibration
avoids expensive calibration procedures during manufacture. The
MAX1416 accommodates negative
temperatures because its input Cold-junction temperature is
measured using a DS600 analog
temperature sensor located at the
thermocouple connector. With
±0.5°C accuracy, the DS600 provides
the most accurate cold-junction
compensation of any analog
temperature-sensor IC on the market. Adding the cold-junction
temperature to the temperature
measured by the ADC corrects for the
parasitic thermocouples created when
the thermocouple connector is linked to the system.
Figure B shows a fully integrated
thermocouple circuit using the
MAX6675 thermocouple-to-digital
converter, a complete thermocouple
interface IC. With the ADC, reference,
gain, and cold-junction compensation
all integrated, the MAX6675 measures
positive temperature values from a
K-type thermocouple and requires no
external components. Using the
MAX6675 thus reduces parts count,
design time, and system complexity.
The maximum measured temperature
is +1024.75°C. The 12-bit resolution
results in an LSB value of 0.25°C
(continued on next page)
5V
0.1μF
20pF
CLKIN
10μF
VDD
20pF
RESET
CLKOUT
PCC-SMP-K-R
ECS-49-20-1
5V
CS
AIN1+
THERMOCOUPLE
CONNECTOR
AIN1-
MAX1416
SCLK
CLOSE
PROXIMITY
AIN2+
VDD
DOUT
AIN2VOUT
DS600
CTG
GND
DIN
REF+
REF-
5V
DRDY
GND
IN
OUT
0.1μF
MAX6133
GND
Figure A. A thermocouple measurement circuit in which the MAX1416 measures the thermocouple output and the DS600
measures the cold-junction temperature.
www.digikey.com/maxim-industrial
73
Sensors
Temperature sensing
Complete thermocouple interface designs eliminate external components,
use less space (continued)
For more information on temperature sensing, please refer to Maxim’s Thermal
Management Handbook at: www.maxim-ic.com/thermal-handbook.
3.3V
VCC
0.1µF
SO
GND
MAX6675
SCK
TO MICROCONTROLLER
CS
T+
T-
Figure B. The MAX6675 is a complete thermocouple-to-digital converter for
K-type thermocouples.
74
Maxim Industrial Solutions
Sensors
Current, light, and proximity sensing
Current, light, and proximity sensing
Overview
These current-sensing techniques
employ current-sense amplifiers
which are available in multiple
configurations, or transimpedance
amplifiers (TIAs). Each type of current-sensing amplifier is
discussed below.
Current sensing is important in many
applications and can be categorized
into two popular approaches.
• In one approach current sensing
is commonly used with higher
currents and often in power-supply
monitoring. Typical applications
include short-circuit detection,
transient detection, and reversebattery detection.
Current sensing using
current-sense amplifiers
A variety of techniques are used
to measure current, but by far the
most popular is with a current-sense
resistor. The basic principle of this
approach is to amplify the voltage
drop across the current-sense resistor
by using an op-amp-based differential
gain stage, and then to measure
the resulting voltage. While discrete
components can be used to build the
amplifier circuit, integrated currentsense amplifiers have significant
advantages over discrete implementations: better temperature drift,
• Current sensing is also used in
applications that require much
lower levels of current detection
(down in the micro-amps), such as
photodiodes that generate a small
amount of current when exposed
to light. Common applications are
ambient light sensing, proximity
detection, and light absorption-/
reflection-based chemical process
monitoring. SENSOR AND
NETWORK
AFE
FILTER
smaller PC-board (PCB) area, and
the ability to handle wide commonmode ranges.
Most current-sensing applications employ either the low-side
or the high-side principle. In the
low-side technique the sense
resistor connects in series with the
ground path. The circuit deals with
ADC
DIGITAL DOMAIN
μC
ADC
ADC
SOURCE
LEVEL
TRANSLATOR
CURRENTSENSE AMP
TOUCH
SCREEN
REFERENCE
Reference
OP AMPS
PRECISION
RESISTORS
LOAD
FILTERS
TRANSCONDUCTANCE
AMPLIFIERS
ISOLATION
= MAXIM SOLUTION
Block diagram of the signal chain in a current-sensing application. For a list of Maxim’s recommended current-sensing solutions, please go to: www.maxim-ic.com/detect.
www.digikey.com/maxim-industrial
75
Sensors
Current, light, and proximity sensing
avoids extraneous resistance in the
ground plane, greatly simplifies the
layout, and generally improves the
overall circuit performance. The
variety of unidirectional and bidirectional current-sense ICs from Maxim
includes devices with and without
internal sense resistors.
a low-input common-mode voltage,
and the output voltage is ground
referenced. However, the low-side
sensing resistor adds undesirable
extraneous resistance in the ground
path. With the high-side principle,
the sense resistor connects in series
with the positive power-supply
voltage. Here the load is grounded, but the high-side resistor must cope
with relatively large common-
mode signals.
High-side current-sense amplifiers
from Maxim employ a currentsensing resistor placed between
the positive terminal of the power
supply and the supply input of the
monitored circuit. This arrangement
Light sensing with transimpedance amplifiers (TIAs)
The second most popular currentmeasurement technique uses an op
amp with very low input-bias current
like a TIA, which converts the current
input into a voltage output. This
principle works for much smaller
currents with large variations like
those generated by photodiodes in
light-sensing applications.
A simple photodiode is a very
accurate transducer for sensing
light. Light sensing is used in
many different applications from
power management based on
sunlight, to sophisticated industrial
process-control applications. Since
illuminance in a given situation can
vary over a broad range (e.g., from
20klx to 100klx), a wide dynamic
range can be a key requirement for a
light sensor. An integrated solution
like the MAX9635*, which integrates
a photodiode, amplifier, and analogto-digital converter (ADC), provides a
dynamic range of 0.03lx to 130,000lx.
Proximity sensing with a
photodiode
While proximity sensing can be
done in many ways, using a photodiode provides higher accuracy and
conserves more power than other
methods. When the light hits the
photodiode, a current is generated
proportional to the strength of
the light intensity. A buffer stage
with low-input noise and high
bandwidth transfers this current to
the rest of the system. An amplifier
with low input-current noise, such
as MAX9945, provides accurate
measurements.
www.maxim-ic.com/detect
*Future product—contact factory for availability.
76
Maxim Industrial Solutions
Sensors
Current, light, and proximity sensing
Improve efficiency and increase reliability by monitoring a system’s power
MAX9922/MAX9923, MAX11601, MAX11607,
MAX11613 families
Here is a very common circuit found in applications for power
monitoring. The MAX9923 current-sense amplifier amplifies the
differential voltage across the current-sense resistor with extremely
low offset and low noise.
The output of the MAX9923 and a resistor-divided output of the
supply is fed to a low-cost, 4-channel 12-bit ADC, the MAX11613.
While two independent supplies are shown here, the ADC could
be monitoring voltage and current on a group of supplies. The
MAX11601, MAX11607, MAX11613 families of ADCs are ideal for this
application as they provide a low-cost, small package (µMAX® or
QSOP) I2C solution with 4 to 12 channels.
Benefits
•• Monitor current directly at the supply
side for highly accurate sensing
–– The MAX9922 allows direct interface to
28V signals
–– The MAX9922/MAX9923 use a patented
spread-spectrum autozeroing technique*
to remove offset and eliminate drift over
time and temperature
–– 12-bit ADCs
•• Versatile and simple solutions
accommodate a range of performance
and cost-based requirements
–– Pin-compatible 8-, 10-, and 12-bit ADCs in
the same package
–– 4 to 12 ADC channels on a 2-wire I2C bus
VSENSE
BATT
1.9V TO
28V
RSB
3.3V
RS+
VDD
MAX9923T
MAX9923H
MAX9923F
ON
RLOAD
RS-
SHDN
OUT
1nF*
MAX11613
FB
REF
GND
OFF
VSENSE
BATT
1.9V TO
28V
RSB
3.3V
RS+
VDD
MAX9923T
MAX9923H
MAX9923F
ON
RLOAD
RS-
SHDN
GND
OUT
1nF*
FB
REF
OFF
*OPTIONAL NOISE REDUCTION
Circuit for monitoring a system’s power supplies.
*U.S. Patent #6,847,257.
www.digikey.com/maxim-industrial
77
Sensors
Current, light, and proximity sensing
Save power, reduce system cost and complexity with a 22-bit, integrated
ambient-light sensor
MAX9635*
Benefits
The MAX9635 is a highly integrated ambient-light sensor with digital
output. Its 1µA current consumption saves power in the system. The
integrated ADC and an I2C communication channel reduce cost by
eliminating external components. Space is also conserved, because
this integrated solution has a 2mm x 2mm footprint. The added functionality of an adaptive gain block makes it easier to integrate this
component into a system.
•• Minimizes power requirements
–– Ultra-low 1µA operating current
consumption
–– VCC is 1.7V to 3.6V and eliminates the
need for different supply rails
•• Adaptable for a wide variety of
applications
–– Wide 0.03lx to 130,000lx sense range
–– Adjustable conversion time provides
flexibility
•• High integration simplifies system
design
–– 6-bit adaptive gain control for
autoranging reduces design complexity –– Optical filters provide an optical
response similar to the human eye, and
block IR and UV light
VCC
PHOTODIODE
WITH OPTICAL FILTER
AND IR/UV REJECTION
6-BIT
ADAPTIVE
GAIN
SDA
DIGITAL LOGIC
SIGNAL
PROCESSING
AND I2C
-
SCL
A0
16-BIT
ADC
+
INT
N
MAX9635*
GND
Typical operating circuit for the 22-bit MAX9635 integrated ambient-light sensor.
*Future product—contact factory for availability.
78
Maxim Industrial Solutions
Sensors
Current, light, and proximity sensing
Get precise measurements in very harsh operating environments
MAX9918/MAX9919/MAX9920
Benefits
The MAX9918/MAX9919/MAX9920 current-sense amplifiers provide
uni-/bidirectional current sensing for very harsh environments where
the input common-mode range can become negative. The amplifiers
have a -20V to +75V common-mode operating range for measuring
the current of inductive loads. The combination of uni-/bidirectional
current measurement measures charge and discharge current into a
system. The 4.5V to 5.5V single-supply operation reduces cost of the
overall system.
•• Industrial-grade products withstand
very harsh operating environments
–– -20V to +75V input common-mode
operating range provides reliability
while measuring the current of inductive
loads
–– -40°C to +125°C automotive temperature
range
•• Integrated functionality reduces system
cost and shortens design cycle
–– Uni-/bidirectional current sensing
–– Single 4.5V to 5.5V supply operation
eliminates the need for a second supply
–– 400µV (max) input offset voltage (VOS)
–– 0.6% (max) gain accuracy error
VCC
VCC
VBATT
φ2B
φ1A
RSENSE
M
MAX9918
MAX9920
A
φ2B
φ1B
ADC
R2
μC
FB
RS+
RS-
OUT
INPUT-STAGE
LEVEL SHIFTER
R1
REFIN
ADJUSTABLE GAIN
SHDN
REF
GND
GND
Typical operating circuit for the MAX9918/MAX9920 current-sense amplifiers for harsh operating environments.
www.digikey.com/maxim-industrial
79
Sensors
Current, light, and proximity sensing
System diagnostics ensure longer up-time in harsh operating environments
MAX4211
Benefits
The MAX4211 is a full-featured, continuous current and power
monitor. The device combines a high-side current-sense amplifier,
1.21V bandgap reference, and two comparators with open-drain
outputs to make detector circuits for overpower, overcurrent, and/or
overvoltage conditions.
•• Real-time power and current
monitoring enhances system reliability
–– ±1.5% (max) current-sense accuracy
–– ±1.5% (max) power-sense accuracy
–– 4V to 28V input-source voltage range
•• Integrated functionality reduces system
cost and shortens design cycle
–– Two integrated uncommitted
comparators allow diagnostic alarm
–– Integrated 1.21V reference output
–– Three current/power-gain options
provide flexibility in any industrial
application
VSENSE
+
4V TO
28V
-
RSENSE
+
-
LOAD
RS+
RS-
VCC
2.7V TO
5.5V
+
-
IOUT
25:1
POUT
1.21V
REFERENCE
INHIBIT
REF
CIN1+
COUT1
CIN1-
LE
CIN2+
COUT2
CIN2-
MAX4211A
MAX4211B
MAX4211C
GND
Typical operating circuit for the MAX4211 power and current monitor for harsh
operating environments.
80
Maxim Industrial Solutions
Sensors
Current, light, and proximity sensing
Improve system accuracy over temperature and minimize the effects of harsh
environmental noise
MAX9939
Benefits
The MAX9939 is a differential-input, programmable-gain amplifier
(PGA). It features SPI™-programmable differential gains from 0.2V/V
to 157V/V; input offset-voltage compensation for on-demand calibration; and an output amplifier that can be configured either as a
high-order active filter or to provide a differential output. Using an
input level-shifting amplifier stage, the MAX9939 processes signals
both above and below ground.
•• Differential input/output configuration
minimizes harsh operating environmental noise
–– Processes signals above and below
ground using an input level-shifting
amplifier stage; is ideal for thermocouple applications
–– Integrates an amplifier for a differentialoutput configuration
•• Integrated functionality reduces system
complexity, maximizes flexibility and
system robustness
–– Optimized for high-signal bandwidth
–– Programmable gain with the SPI controls:
0.2V/V, 1V/V, 10V/V, 20V/V, 30V/V, 40V/V,
60V/V, 80V/V, 119V/V, and 157V/V
–– Embedded input protection to ±16V
–– Integrated amplifier for
RC-programmable active filter
–– Input offset-voltage compensation for
on-demand calibration
VCC
1μF
0.1μF
VCC
VCC
MAX9939
20kΩ
20kΩ
VCC/2
VCC/2
20kΩ
20kΩ
10kΩ
INA+
OUTA
A
RI
LVL
10kΩ
10kΩ
RF
INA-
ASIC
INB
VCC
10kΩ
10kΩ
GAIN
INPUTOFFSETVOLTAGE
TRIM
20kΩ
SPI REGISTERS
SCLK DIN
B
SHUTDOWN
20kΩ
ADC
OUTB
VCC/2
CS
CS
DOUT
SCLK
Functional diagram of the robust MAX9939 PGA.
www.digikey.com/maxim-industrial
81
Sensors
Current, light, and proximity sensing
Maximize system accuracy in photodiode and high-ohmic sensor applications
MAX9945
Benefits
The MAX9945 operational amplifier features an excellent combination
of low-operating power and low-input-voltage noise. MOS inputs
enable the MAX9945 to feature low 50fA input-bias currents and low
(15nV/√Hz) input-current noise. The MAX9945 simplifies the interface
between high-ohmic sensors or low-current TIA applications. •• Improves system’s signal-to-noise ratio
(SNR) for more accurate measurements
–– 50fA low input-bias current
–– 1fA/√Hz low input-current noise
–– 15nV/√Hz low noise
•• High-voltage robust design simplifies
mixed-voltage designs
–– 4.75V to 38V single-supply voltage range
–– ±2.4V to ±19V dual-supply voltage range
–– Rail-to-rail output-voltage swing
VCC
PHOTODIODE
IN-
OUT
MAX9945
SIGNAL
CONDITIONING/
FILTERS
ADC
IN+
VEE
Highly accurate light-sensor interface features the MAX9945 op amp.
82
Maxim Industrial Solutions
Sensors
Hall-effect sensors
Hall-effect sensors
Overview
MAG
NET
Hall-effect sensors are widely used
in applications for status, position,
angular, and proximity detection
and for smart-sensing systems.
Since Hall-effect sensors detect a
magnetic field, they can operate in
harsh environmental conditions.
Their robustness and reliability are
important benefits derived from a
magnetic field.
IC F
LUX
A
CU PP
R LI
R ED
EN
T
VOL HAL
TAG L
E
combines two Hall-effect sensors
and digital logic to provide position
and direction outputs. As an additional help for detecting mechanical
movements, single and dual Halleffect switches can integrate a
Hall-effect sensor, an amplifier, and
an output stage. A Hall-effect switch
can, for example, be placed on a
stationary part and a magnet placed
in a mechanical moving arm. When
the arm aligns with the stationary
part, the Hall-effect switch detects
Hall-effect sensors are used in motor
applications where the speed,
position, and direction of motors can be sensed and communicated to
the system for real-time feedback. If
there is an interruption to the motor,
the sensor detects it so corrective
action can be taken.
Typically, to detect the direction
of movement, two Hall-effect
sensors are used. Maxim’s MAX9641*
the position and forwards the information to the microprocessor.
Hall-effect sensors improve robustness and repeatability compared
to mechanical approaches. These
sensors provide better reliability than
photointerrupter-based systems
which are not reliable in dusty, humid environments.
www.maxim-ic.com/detect
*Future product—contact factory for availability.
www.digikey.com/maxim-industrial
83
Sensors
Hall-effect sensors
Simplify motion detection and system design with dual Hall-effect switch
MAX9641*
Benefits
The MAX9641 is an ultra-low-power, dual, Hall-effect switch with
adjustable threshold operation and selectable sampling frequency.
Three programmable sampling periods (160µs, 500µs, and 50ms)
provide flexibility for choosing the operating speed. The operating
point of the Hall-effect switch can be easily adjusted to three points
by setting the adjust pin. With logic communication built in, the
user can retrieve information about the speed and direction of the
magnet’s movement. Combining two Hall-effect sensors into one
chip reduces overall system cost.
•• Simplifies system design with enhanced
functionality
–– User-selectable sampling period
of 160µs, 500µs, and 50ms with an
adjustable RATE pin
–– The switch’s threshold point can be
easily chosen by setting the ADJ pin
•• Simplifies the measurement of speed
and direction
–– Dual Hall-effect sensors integrated in a
single IC
•• Reduces system cost
–– Information for both direction and
speed is gathered with a single IC
–– 1.7V to 5.5V supply voltage range is
compatible with many system designs
VDD
N
S
S
N
MAX9641*
MODE
GND
OUT
µC/FPGA/
CHIPSET
PROCESSOR
DIR
3.3V
OUT
DIR
Dual Hall-effect switch solution.
*Future product—contact factory for availability.
84
Maxim Industrial Solutions
Sensors
Sensor communications interface
Sensor communications interface
A sensor communicates its sensed
information with analog or digital
techniques. Analog techniques are
based on voltage or current loops.
Digital information is communicated
with CAN, CompoNet®, IO-Link®,
RS-485, and other data interfaces.
Also, when an object like a piston in
a valve reaches a predefined critical
distance, the sensor detects and
communicates this to the programmable-logic-controller (PLC) system
through a binary interface.
Sensor interfaces have to be robust
against all forms of mishandling and
EMI, since the industrial environments are harsh.
Binary sensors only transmit single-bit
information. Typically, the presence
or absence of an object is detected
and communicated with a logic level.
www.maxim-ic.com/sensor
www.digikey.com/maxim-industrial
85
Sensors
Sensor communications interface
Fault-protected RS-485 transceivers make equipment more robust
MAX13448E, MAX3440E–MAX3444E,
MAX13442E/MAX13443E/MAX13444E,
MAX3430
Benefits
In applications where power and data are distributed over the same
cable, there is a potential for miswiring, cable shorts, or surges on the
communication bus. Maxim’s RS-485 transceivers offer fault protection up to ±80VDC . DE
•• Flexible configurations interface with
multiple systems
–– Wide 3.3V to 5V supply range –– Interfaces with full- and half-duplex
systems
Y
DI
Z
A
DI
•• Reduce board space by 25% with
integrated fault-protection circuitry
–– Highest fault protection from an
integrated transceiver
–– Fault protection up to ±80V
B
Reduces
external
components,
saves up to
25% board
space
RE
ZENERS
POLYSWITCH
LIMITERS
•• High integration reduces bill of
materials (BOM) complexity and cost
–– Integrated slew-rate limiting for
error-free data transmission
–– True fail-safe operation
–– Hot-swap operation
•• Robust operation in harsh
environments
–– ±15kV ESD protection
VCC
DE
Y
DI
D
Z
MAX13448E
RO
A
R
B
N.C.
GND
RE
Part
VCC Supply (V)
Configuration
Fault Protection (V)
3.3 to 5
Full
±80
MAX3440E–44E
5
Half
±60
MAX13442E/43E/44E
5
Half
±80
3.3
Half
±80
MAX13448E
MAX3430
Maxim’s RS-485 family offers high levels of flexibility and integration.
86
Maxim Industrial Solutions
Sensors
Sensor communications interface
Reduce PCB footprint with an IO-Link/binary sensor interface
MAX14820*
Benefits
The MAX14820 is a transceiver with a 24V binary interface for sensors
and actuators. Designed for IO-Link device applications, it supports
all the specified IO-Link data rates. The MAX14820 contains additional 24V digital inputs and outputs (I/Os). Two regulators generate
common sensor signals and conditioning power requirements: 5V
and 3.3V. The drivers are configurable to PNP, NPN, and push-pull.
Configuration, monitoring, and alarms are accessed through an SPI™
interface. The device is thermally self-protected and all 24V interface
pins are protected against reverse-polarity, shorts, and ESD.
•• Industry’s smallest package for
compact designs
–– Tiny 2.5mm x 2.5mm WLP and 4mm x
4mm TQFN
–– Requires minimal external components
•• Integration of all high-voltage
functions optimizes sensor circuit partitioning, saves board space
–– Integrated high-voltage regulators
–– Undervoltage detection –– Two output drivers and two receivers
•• Single solution fits multiple application
requirements, reduces inventory
complexity
–– Suitable for sensors and actuators
–– Suitable for binary sensor applications
–– Dual outputs and inputs fit most sensor
needs
–– Dual output supplies power signal
conditioning
5V
0.1μF
3.3V
0.1μF
0.1μF
10kΩ
VCC
MICROCONTROLLER
GND
VL
GPIO2
UV
CS
SCLK
SDO
SDI
CS
SCLK
SDO
SDI
IRQ
WU
RX
RX
TX
TXC
RTS
TXEN
GPIO1
LO
TXQ V33
V5
LDOIN VP
VCC
1μF
L+
DO
MAX14820*
C/Q
GND
LI
1
2
3
4
L-
DI
The MAX14820 IO-Link/binary-sensor interface reduces PCB footprint.
*Future product—contact factory for availability.
www.digikey.com/maxim-industrial
87
Sensors
Recommended solutions
Recommended solutions
Pressure sensors and weigh scale
Part
Description
Features
Benefits
ADCs
MAX1415/16
MX7705
16-bit, low-power, 2-channel, sigma- Two differential channels; PGA; single-supply
delta ADCs
operation
Highly flexible ADC; interfaces with a wide range of
sensors
MAX1400/01/02/03
18-bit, 5-channel delta-sigma ADCs
Three differential channels; PGA; precision current
sources for excitation; burn-out detection
High integration produces a more precise sensor
that measures both pressure and temperature with
one ADC
MAX11040
24-bit, 4-channel, simultaneoussampling sigma-delta ADC
Cascadable up to 32 channels; 106dB SNR at
16ksps; overvoltage protection (OVP)
Eases design interface to sensors that require
multichannel accurate amplitude and phase
information
MAX11200*/01*/02*
Ultra-low-power, sigma-delta ADCs
21-bit noise-free range at 10sps; 3V supply;
0.45mW; four general-purpose inputs/outputs
(GPIOs)
21 bits of noise-free range with minimal impact on
power budget
Sensor signal conditioners
MAX1452
Low-cost, precision, analog sensor
signal conditioner
Multitemperature calibration; current and voltage
excitation; fast 150ns response; single-pin
programmable; 4–20mA applications
Provides a flexible signal-conditioning platform for
a wide range of sensor applications, thus reducing
inventory
MAX1464
Low-power, low-noise, multichannel, Integrates 16-bit ADC, DACs, and CPU;
digital sensor signal processor
programmable compensation algorithm; digital,
analog, and PWM outputs; 4–20mA applications
Accurate signal conditioner interfaces directly with
microcontroller to save space
MAX9617/18
Ultra-precision, zero-drift op amps
1.5 MHz gain bandwidth (GBW); 59µA supply
current; 10µV (max) zero-drift input offset voltage
(VOS); single and dual packaging versions
Provide high-precision measurements for a wide
variety of low-frequency applications
MAX9943/44
High-voltage, precision, low-power
op amps
Wide 6V to 38V supply range; 2.4 MHz GBW
Design flexibility for a wide range of applications
Amplifiers
For a list of Maxim’s recommended pressure-sensor solutions, please go to: www.maxim-ic.com/psi.
*Future part—contact factory for availability.
88
Maxim Industrial Solutions
Sensors
Recommended solutions
Recommended solutions (continued)
Temperature sensing
Part
Description
Features
Benefits
Thermal management
DS600
Precision analog-output temperature Industry’s highest accuracy analog temp sensor:
sensor
±0.5°C from -20ºC to +100ºC
Best cold-junction compensation accuracy for
superior thermocouple measurement
DS7505
Low-voltage, precision, digital
thermometer and thermostat
±0.5°C accuracy from 0ºC to +70ºC; 1.7V to 3.7V
operation; industry-standard pinout
Industry-standard pinout allows easy accuracy
upgrade and supply-voltage reduction from LM75
DS18B20
Precision 1-Wire digital temperature
sensor
±0.5ºC accuracy from -10°C to +85°C; 1-Wire
interface; 64-bit factory-lasered ID code
Connects multiple precision temperature sensors
with fewer wires than any competitive solution
MAX6675
K-type thermocouple-to-digital
converter
Built-in cold-junction compensation
Simplest thermocouple interface; no external
components needed
ADCs
MAX1300*/01/02*/03 16-bit, 8-/4-channel SAR ADCs with Input range from ±12V to 0 to 2.048V; ±16.5V
software-programmable input ranges overvoltage-protected inputs; PGA; internal
reference
Reduce design complexity when working with
sensors with multiple output ranges
MAX1415/16
MX7705
16-bit, low-power, 2-channel,
sigma-delta ADCs
Flexible ADC interfaces with a wide range of sensors
MAX1400/01/02/03
18-bit, 5-channel, sigma-delta ADCs Three differential channels; precision current
sources for excitation; burn-out detection
A single ADC simplifies temperature-sensor design
for accurate thermocouple and RTD measurement
MAX11200*/01*/02*
Ultra-low-power, sigma-delta ADCs
21-bit noise-free range at 10sps; 3V supply;
0.45mW; 4 GPIOs
21 bits of noise-free range with minimal impact on
power budget
MAX9617/18
Ultra-low-power, zero-drift op amps
1.5 MHz GBW; 59µA supply current; 10µV (max)
Provide high-precision measurements for a wide
zero-drift input offset voltage (VOS); single and dual variety of low-frequency applications
packaging versions
MAX9943/44
High voltage, precision, low power
op amps
Wide 6V to 38V supply range; 2.4 MHz GBW
Design flexibility for a wide range of applications
MAX9939
SPI programmable-gain amplifier
(PGA) with on-demand calibration
and differential in/out configuration
Input supports negative voltages; wide range of
gain configurations; input-error nulling feature
Calibration on-demand improves system accuracy;
minimizes harsh environmental noise
Two differential channels; PGA; single supply
Amplifiers
For a list of Maxim’s recommended temperature-sensor solutions, please go to: www.maxim-ic.com/-40+85.
*Future part—contact factory for availability.
www.digikey.com/maxim-industrial
89
Sensors
Recommended solutions
Recommended solutions (continued)
Light sensing
Part
Description
Features
Benefits
ADCs
MAX1168/67
MAX1162
16-bit, 200ksps, 8-/4-/1-channel
SAR ADCs
16-bits, no missing codes; single 5V supply;
unipolar 0 to 5V input range
Flexible and accurate solution for multichannel
applications
MAX11200*/01*/02*
Ultra-low-power, sigma-delta ADCs
21-bit noise-free range at10sps; 3V supply;
0.45mW; 4 GPIOs
Use lower power while enabling accurate
measurements over a 20klx to 100klx range
MAX9635*
Ambient-light sensor with integrated
ADC
1µA ultra-low power; 22-bit wide dynamic-range
with automatic gain control (AGC)
Integrated ambient-light sensor saves power; reduces
system cost and complexity
MAX9945
Low-noise, MOS-input, low-power
op amp
4.75V to 38V supply voltage range; low input-bias
current; low input-current noise
Low input-bias current (fA) maximizes system
accuracy
200mA output-drive capability; 10MHz GBW;
10µV/s high slew rate
Provide drive to allow extended distance between
sensors and acquisition system
Amplifiers
MAX4230–MAX4234 High-output-drive, rail-to-rail I/O op
amp series
MAX4475–MAX4478 Low-distortion, CMOS-input op amp 0.0002% THD+N; low input-bias current; 10MHz
series
GBW
Accurately reproduce the input signal for the ADC
*Future part—contact factory for availability.
90
Maxim Industrial Solutions
Sensors
Recommended solutions
Recommended solutions (continued)
Current sensing
Part
Description
Features
Benefits
ADCs
MAX11600–
MAX11605
Multichannel, low-power, ADCs with
I2C interface
Low cost; 8-/12-bit; 4-/8-/12-channels; differential Sense multiple currents and voltages at low cost
inputs; low power (6µA at 1ksps);I2C
MAX11606–
MAX11611
MAX11612–
MAX11617
MAX11618*–
MAX11625*
Multichannel, FIFO ADCs with an SPI Low cost; 8-/12- bit; 8-/12-/16-channels;
interface
differential inputs; internal FIFO; SPI
Sense multiple currents and voltages at low cost with
a family of SPI ADCs
MAX9918/19/20
Precision, uni-/bidirectional current- -20V to +75V input common-mode range (CMR);
sense amplifiers
400µV (max) input offset voltage (VOS); choice of
gains
Precise current monitoring for even negative
common-mode voltages; needs no additional
circuitry
MAX9922/23
Ultra-precision, high-side currentsense amplifiers
25µV (max) offset voltage (VOS); > 0.5% gain
accuracy; choice of gains
Allows precise current measurements even at very
small sense voltages
MAX9928F/29F
Ultra-small, uni-/bidirectional, highside current-sense amplifiers
-0.1V to +28V input CMRR with 20µA quiescent
supply current; choice of gains
Save space for battery-monitoring applications
MAX4211
High-side power and current monitor Real-time power and current monitor;
with diagnostics for state of health
programmable diagnostic detector
MAX11626*–
MAX11633*
MAX11634*–
MAX11637*
MAX11638*–
MAX11643*
Amplifiers
Integrated solution for current monitoring; speeds
design
For a list of Maxim’s recommended current-sensing solutions, please go to: www.maxim-ic.com/detect.
*Future part—contact factory for availability.
www.digikey.com/maxim-industrial
91
Sensors
Recommended solutions
Recommended solutions (continued)
Hall-effect sensors
Part
Description
Features
Benefits
Amplifiers
MAX9639*
Ultra-low-power, Hall-effect sensor
50ms sampling rate; 1.7V to 5.5V operation; three
threshold points of 1.5mT, 3mT, and 5mT
Integrated sensor and amplifier reduce cost
MAX9640*
Ultra-low-power, Hall-effect sensor
50ms sampling rate; 1.7V to 5.5V operation; sign
output
Reduces system cost by giving the direction of an
applied magnetic field
MAX9641*
Ultra-low-power, dual, Hall-effect
sensor
Selection of 160µs/500µs/50ms sample periods;
three threshold points of 1.5mT, 3mT, and 5mT;
gives direction and speed of magnet movement
Simplifies Hall-effect system by integrating
components with adjustable features
For a list of Maxim’s recommended position-sensing solutions, please go to: www.maxim-ic.com/detect.
Sensor communications interface
Part
Description
Features
Benefits
Transceivers
MAX14820*
IO-Link sensor actuator interface
MAX13442E/43E/44E Fault-protected RS-485 transceivers
Tiny 2.5mm x 2.5mm WLP and 4mm x 4mm TQFN
packages; dual 24V outputs and dual 24V inputs;
300mA drive capability; IO-Link wake-up detection
IO-Link/binary sensor interface reduces PCB
footprint
±80V fault-protected RS-485; half-duplex; 5V
(250kHz/10MHz)
Simplify design by eliminating external components
such as transient voltage suppressors (TVSs) and
overcurrent protectors
For a list of Maxim’s recommended sensor-communications solutions, please go to: www.maxim-ic.com/sensor.
*Future part—contact factory for availability.
92
Maxim Industrial Solutions
Motor control
Motor Control
Overview
Overview
DC motors: low cost and accurate
drive performance
Electric motors consume almost 50%
of the world’s electricity. With the
cost of energy rising steadily, industry
is focused on replacing inefficient
constant-speed motors and drives
with microprocessor-based, variablespeed drives. This new motor-control
technology will reduce energy
consumption by more than 30%
compared to the older drives. While
these variable-speed controllers add
cost to a motor, the forecasted
energy savings and increased motor
functionality should easily offset
those initial expenses within a few years.
A DC motor was among the first motor
types put to practical use, and it is still
popular where low initial cost and
excellent drive performance are
required. In its simplest form, the stator
(i.e., the stationary part of the motor) is
a permanent magnet, and the rotor
(i.e., the rotating part of the motor)
carries an armature winding connected
to a mechanical commutator which
switches current on and off to the
winding. The magnet establishes the
field flux which interacts with the
armature current to produce the
electromagnetic torque, thereby
enabling the motor to perform work.
The motor’s speed is controlled by
adjusting the DC voltage applied to the armature winding.
www.digikey.com/maxim-industrial
DC motors are also widely used in
servo applications where speed and
accuracy are important. To meet
speed and accuracy requirements,
microprocessor-based closed-loop
control and information about rotor
position are essential. Maxim’s
MAX9641* Hall-effect sensor provides
information about rotor position.
THREE-PHASE BRIDGE
MOTOR
GATE
DRIVER
HALL-EFFECT SENSOR
RESOLVER
ENCODER
Popular motor designs
The DC motor, brushless DC, and
AC induction motor are the popular
motor designs used in today’s industrial applications. Each of these
motor types has its own unique
characteristics, but they all operate
on the same basic electromagnetic
principle: when a conductor carrying
current, such as a wire winding, is
located in an external magnetic field
perpendicular to the conductor, then
the conductor will experience a force
perpendicular to itself and to the
external magnetic field.
Depending on the application, a
full-bridge, half-bridge, or just a
step-down converter is used to drive
the armature winding. The switches
in these converters are pulse-width
modulated (PWMed) to achieve the
desired voltage. Maxim’s high-side or
bridge-driver ICs like the MAX15024/
MAX15025 can be used to drive the
FETs in the full- or half-bridge circuit.
TEMP
SENSOR
LOGIC
CURRENTSENSE
AMPLIFIER
CURRENTSENSE
AMPLIFIER
ADCs
SPEED
DIRECTION
MICROCONTROLLER
TORQUE
DC-DC
POWER
RS-485
SUPERVISORS
= MAXIM SOLUTION
Block diagram of a typical industrial motor control.
For a list of Maxim’s recommended motor-drive solutions, please go to: www.maxim-ic.com/motordrive.
95
Motor Control
Overview
AC induction motors: simplicity
and ruggedness
An AC induction motor is popular in
industry because of its simplicity and
ruggedness. In its simplest form, this
motor is a transformer with the
primary-side voltage connected to
the AC-power-voltage source and the
secondary side shorted to carry the
induced secondary current. The name
“induction” motor derives from this
induced secondary current. The stator
carries a three-phase winding and the
rotor is a simple design, commonly
called a “squirrel cage,” in which the
copper or aluminum bars are shortcircuited at both the ends by castaluminum end rings. The absence of
rotor windings and brushes makes
this motor design especially reliable.
half bridges in which the top and the
bottom switch are controlled in a
complementary fashion. Maxim offers multiple half-bridge drivers like the MAX15024/MAX15025
which control the top and bottom
FETs independently.
Precise measurement of threephase motor current, rotor position,
and rotor speed are necessary for
efficient closed-loop control of
an induction motor. Maxim offers
many high-side and low-side current
amplifiers, Hall-effect sensors, and
simultaneous-sampling analogto-digital converters (ADCs) to
accurately measure these parameters
in the harshest environments.
A microprocessor uses data on the
current and position to generate
logic signals for the three-phase
bridge. A popular closed-loop
control technique called vector
control decouples the vectors of field
current from the stator flux so that it
can be controlled independently to
provide a fast transient response.
Brushless DC motors: high
reliability and high-output power
Rotor and stator of an induction motor.
When operated from the 60Hz voltage,
the induction motor operates at a
constant speed. However, when power
electronics and a microprocessorbased system are used, the motor’s
speed can be varied. The variablespeed drive consists of an inverter,
signal conditioner, and microprocessorbased control. The inverter uses three
A brushless DC (BLDC) motor has
neither commutator nor brushes, so
it requires less maintenance than a
DC motor. It also offers more output
power per frame size compared to
induction and DC motors.
The stator of the BLDC motor is quite
similar to that of the induction motor.
The BLDC motor’s rotor, however,
can take different forms, but all are
permanent magnets. Air-gap flux
is fixed by the magnet and is unaffected by the stator current. The
BLDC motor also requires some
form of rotor position sensing. A
Hall-effect device embedded in the
stator is commonly used to sense
the rotor’s position. When the rotor’s
magnetic pole passes near the Halleffect sensors, a signal indicates
whether the north or the south pole
passed. Maxim offers several Halleffect sensors like the MAX9641*,
which simplifies designs and reduces
system costs by integrating two
Hall-effect sensors and digital logic to provide both positional and
directional outputs of the magnet.
The importance of sensors,
signal conversion, and data
interfaces
Several types of sensors provide
feedback information in the motorcontrol loop. These sensors also
improve reliability by detecting
fault conditions that can damage
the motor. The following sections
examine the role of sensors in motor
control in greater detail. Specific
attention will be given to currentsense amplifiers, Hall-effect sensors,
and variable-reluctance (VR) sensors.
Other important topics include
monitoring and controlling multichannel currents and voltages with
high-speed analog-to-digital signal
conversion (ADCs), and the encoder
data interfaces needed for highaccuracy motor control.
www.maxim-ic.com/motordrive
* Future product—contact factory for availability.
96
Maxim Industrial Solutions
Motor Control
Monitoring and measuring current for optimal motor control
Monitoring and measuring current for optimal motor control
Current monitoring
Current is a common signal to be
sensed, monitored, and fed back
to the motor-control loop. Currentsense amplifiers make it easier to
monitor the current into and out
of the system with a high level of
precision. If current-sense amplifiers
are used, no transducer is needed,
as the electrical signal itself is being
measured. Current-sense amplifiers
detect shorts and transients, and
they monitor power and reversebattery conditions.
Current measurement
There is a variety of techniques to
measure current, but by far the most
popular uses a current-sense resistor.
In this technique the voltage drop
across the current-sense resistor is
first amplified by an op amp set up
in a differential gain stage, and then
measured. Traditionally, this approach
has been implemented with discrete
components. However, discrete
solutions also introduce some disadvantages such as the requirement
for matched resistors, poor drift, and
www.digikey.com/maxim-industrial
a larger solution area. Fortunately,
these multiple and varied disadvantages can be overcome by
integrating current-sense amplifiers into the design. Not only do
the amplifiers measure the current,
but they also sense the direction
of current, accommodate wide
common-mode ranges, and provide
more precise measurement.
Current measurement employs either
the low-side principle in which the
sense resistor connects in series with
the ground path, or the high-side
principle in which the sense resistor
connects in series with the hot wire. In
low-side measurement, the circuit has
a low-input common-mode voltage,
and the output voltage is ground
referenced. The low-side resistor
adds undesirable extraneous resistance in the ground path. In high-side
measurement, the load is grounded,
but the high-side resistor must cope
with relatively large common-mode
signals. High-side sensing also allows
detection of fault conditions such
as the motor case or winding that
shorts to ground.
High-side current-sense amplifiers
like the MAX4080/MAX4081 employ
a current-sensing resistor placed
between the positive terminal of
the power supply and the supply
input of the monitored circuit. This
arrangement avoids extraneous resistance in the ground plane, greatly
simplifies the layout, and generally
improves the overall circuit performance. Maxim’s unidirectional and
bidirectional current-sense ICs like
the MAX9918/MAX9919/MAX9920 are
available with or without internal sense
resistors. This variety of parts adds
considerable flexibility to designs
and simplifies part selection for a wide
variety of ADCs and applications.
97
Motor Control
Monitoring and measuring current for optimal motor control
Precise current measurements ensure better motor control
MAX9918/MAX9919/MAX9920
Benefits
The MAX9918/MAX9919/MAX9920 are current-sense amplifiers with
a -20V to +75V input range. The devices provide unidirectional/
bidirectional current sensing in very harsh environments where the
input common-mode range can become negative. Uni-/bidirectional
current sensing measures charge and discharge current in a
system. The single-supply operation shortens the design time and
reduces the cost of the overall system.
•• Provide reliable operation in harsh
motor-control environments
–– 400µV (max) input offset voltage (VOS)
–– -20V to +75V common-mode voltage
range provides reliability for measuring
the current of inductive loads
–– -40°C to +125°C automotive temperature
range
•• Integrated functionality reduces system
cost and shortens design cycle
–– Uni-/bidirectional current sensing
–– Single-supply operation (4.5V to 5.5V)
eliminates the need for a second supply
–– 400µV (max) input offset voltage (VOS)
–– 0.6% (max) gain accuracy error
VCC
VCC
VBATT
φ2B
φ1A
RSENSE
M
MAX9918
MAX9920
A
φ2B
φ1B
ADC
R2
μC
FB
RS+
RS-
OUT
INPUT-STAGE
LEVEL SHIFTER
R1
REFIN
ADJUSTABLE GAIN
SHDN
REF
GND
GND
The MAX9918/MAX9920 current-sense amplifiers provide precise uni-/bidirectional current sensing in very harsh environments.
98
Maxim Industrial Solutions
Motor Control
Sensing motor speed, position, and movement
Sensing motor speed, position, and movement
Overview
Hall-effect sensors are used to sense
the speed, position, and direction
of motors. With integrated device
logic, the sensors then communicate
that data to the system for real-time
feedback. The sensor also detects
and reports any interruption to
the motor so corrective action can
be taken. Typically, to detect the
direction of movement two Halleffect sensors are used.
Commutation can be synchronized
to Hall edges if the system has the
same number of Hall-effect devices as
motor phases, and if the mechanical
geometry of the Hall-effect devices
is correlated with the electrical
geometry of the motor phases.
Maxim’s MAX9641* combines two
Hall-effect sensors and sensor
signal conditioning to provide both
positional and directional outputs.
Hall-effect sensors can also be used
with special Hall-effect sensor
interface products like the MAX9621.
The interface devices provide several
functions: protect against supply
transients, sense and filter the current
drawn by the Hall-effect sensors, and
diagnose and protect against faults.
Hall-effect sensors improve robustness and repeatability, compared to
mechanical photointerrupter-based
systems which are compromised
in environments with dust and
humidity. Since Hall-effect sensors
detect the magnetic field produced
by a magnet or current, they can
operate continuously in such harsh
environmental conditions. In some applications vibration, dust,
and high temperature cause active
sensors to operate improperly. In
these situations passive elements
can be used to sense the motor’s
operation and feed that data to
the system with an interface IC.
Alternatively, variable-reluctance (VR)
sensors can be used in these extreme
operating conditions. VR sensors like the MAX9924–
MAX9927 have a coil to sense the
speed and rotation of motors. When
the toothed wheel of the shaft
attached to a motor passes by the
face of the magnet, the amount of
magnetic flux passing through the
magnet and, consequently, the coil
varies. When the tooth is close to
the sensor, the flux is at a maximum.
When the tooth is further away, the
flux drops off. The rotating toothed
wheel results in a time-varying flux
that induces a proportional voltage
in the coil. Subsequent electronics
then process this signal to get a
digital waveform that can be counted
and timed more readily. Integrated
VR-sensor interface solutions
possess many advantages over
other solutions, including enhanced
noise immunity and accurate phase
information.
*Future product—contact factory for availability.
www.digikey.com/maxim-industrial
99
Motor Control
Sensing motor speed, position, and movement
Simplify system design with flexible operating inputs
MAX9641*
Benefits
The MAX9641 is an ultra-low-power, dual Hall-effect switch. Three
programmable sampling periods of 160µs, 500µs, and 50ms give the
designer flexibility to choose the operating speed. By setting the
adjust pin, the MAX9641’s operating point can be easily adjusted
to three points which accommodate many different magnetic
materials. Integrating two Hall-effect sensors into one chip reduces
the overall system’s cost. The user retrieves the information about the
speed and direction of the magnet’s movement with built-in logic
communication.
•• Enhanced functionality simplifies
motor-control design
–– Select the sampling period of 160µsec,
500µs, and 50ms by simply adjusting the
RATE pin
–– Choose the threshold point of the switch
by setting the ADJ pin
VDD
N
S
S
N
MAX9641*
MODE
GND
OUT
•• High integration simplifies measurement
of speed and direction and reduces
system cost
–– Two Hall-effect sensors in a single IC
–– Direction and speed information is
gathered simultaneously
–– 1.7V to 5.5V supply voltage range is
compatible with many system designs
µC/FPGA/
CHIPSET
PROCESSOR
DIR
3.3V
OUT
DIR
Dual Hall-effect switch solution.
*Future product—contact factory for availability.
100
Maxim Industrial Solutions
Motor Control
Sensing motor speed, position, and movement
Highly accurate, reliable monitoring of motor speed and position with a sensor
interface
MAX9621
Benefits
The MAX9621 is a dual, 2-wire Hall-effect sensor interface with
analog and digital outputs. This device enables a microprocessor
to monitor the status of two Hall-effect sensors, either through the
analog output by mirroring the sensor current for linear information,
or through the filtered digital output. The input current threshold
can be to the magnetic field. The MAX9621 provides a supply current
to two 2-wire Hall-effect sensors and operates in the 5.5V to 18V
voltage range. The high-side current-sense architecture eliminates
the need for a ground-return wire without introducing ground shift.
This feature saves 50% wiring cost.
•• Integrated functionality eases motorcontrol design, reduces system cost
–– Select the analog or digital output
to monitor the Hall-effect sensor’s
condition
–– High-side current-sense architecture
eliminates the need for a ground-return
wire and saves 50% wiring cost
•• Reliable operation in a harsh
environment
–– Protects against up to 60V supply
voltage transients
–– Detects a short-to-ground fault
condition to protect the system
1.8V TO 5.5V
0.1μF
BATTERY: 5.5V TO 18V
OPERATING,
60V WITHSTAND
RPU
10kΩ
RSET
ISET
REFERENCE
RPU
10kΩ
BAT
REF
SLEEP-MODE
CONTROL
BAT
SLEEP
100kΩ
AOUT1
ADC
5kΩ
N
S
ECUCONNECTOR
DOUT1
IN1
REF
FILTER
0.01μF
MICROPROCESSOR
INPUT
SHORT
DETECTION
REMOTE
GROUND
BAT
MAX9621
AOUT2
ADC
5kΩ
IN2
N
S
DOUT2
0.01μF
REF
REMOTE
GROUND
FILTER
GND
Functional diagram of the MAX9621 Hall-effect sensor interface.
www.digikey.com/maxim-industrial
101
Motor Control
Sensing motor speed, position, and movement
Improve performance and reliability in motor applications with a differential VR
sensor interface
MAX9924–MAX9927
Benefits
The MAX9924–MAX9927 VR, or magnetic coil, sensor interface
devices are ideal for sensing the position and speed of motor shafts,
camshafts, transmission shafts, and other rotating wheel shafts.
These devices integrate a precision amplifier and comparator
with selectable adaptive peak threshold and zero-crossing circuit
blocks that generate robust output pulses, even in the presence
of substantial system noise or extremely weak VR signals. The
MAX9924–MAX9927 interface to both single-ended and differentialended VR sensors.
•• High integration provides accurate
phase information for precise sensing
of rotor position
–– Differential input stage provides
enhanced noise immunity
–– Precision amplifier and comparator
allow small-signal detection
–– Zero-crossing detection provides
accurate phase information
MOTOR BLOCK
VR SENSOR
MAX9924
DIFFERENTIAL
AMPLIFIER
ADAPTIVE/MINIMUM
AND
ZERO-CROSSING
THRESHOLDS
μC
INTERNAL/EXTERNAL
BIAS VOLTAGE
Simplified block diagram of the MAX9924 VR sensor interface to a motor.
102
Maxim Industrial Solutions
Motor Control
Monitoring and controlling multichannel currents and voltages
Monitoring and controlling multichannel currents and voltages
Overview
To monitor and control a motor,
multiple currents and voltages
need to be measured and the phase
integrity between the channels
preserved. Designers are faced
with two choices for the ADC
architecture: use multiple singlechannel ADCs in parallel, a design
that makes it very difficult to synch
up the conversion timing; or use a
simultaneous-sampling ADC. The
simultaneous-sampling architecture
uses either multiple ADCs in a single
package, all with a single conversion
trigger, or with multiple sampleand-hold amplifiers (also referred
to as track-and-hold amplifiers) on
the analog inputs. In the case of
multiple sample-and-hold amplifiers,
a multiplexer is still used between
www.digikey.com/maxim-industrial
the multiple analog inputs and the
single ADC. Simultaneous sampling
eliminates the need for complicated
digital-signal-processing algorithms.
Sampling speeds of 100ksps or more
are common for motor-control applications. At these speeds the ADC
continuously monitors the motor for
any indication of errors or potential
damage. At the first sign of trouble,
the system can correct itself or shut
down when necessary. If the ADC
does not sample fast enough, an
error condition might not be identified early enough to be addressed.
applications, however, 16 bits of
resolution are a more common
standard. A high-performance
16-bit ADC like the MAX11044 or
MAX11049 allows a system to achieve
better than 90dB of dynamic range.
The amount of dynamic measurement
range varies for each motor-control
application. In some cases 12 bits
of resolution are sufficient. For
the more precise motor-control
Maxim offers a broad portfolio
of simultaneous-sampling ADCs
designed for motor control. Devices
have both serial and parallel interfaces, and 12-, 14-, or 16-bit operation.
103
Motor Control
Monitoring and controlling multichannel currents and voltages
Resolve very fine motor adjustments and operate higher accuracy systems with
simultaneous-sampling ADCs
MAX11044/MAX11045/MAX11046
MAX11047/MAX11048/MAX11049
Benefits
The MAX11044–MAX11049 ADCs are an ideal fit for motor-control
applications that require a wide dynamic range. With a 93dB signalto-noise ratio (SNR), these ADCs detect very fine changes to motor
currents and voltages, which enables a more precise reading of
motor performance over time. The MAX11046/MAX11045/MAX11044
simultaneously sample eight, six, or four analog inputs, respectively.
All ADCs operate from a single 5V supply. The MAX11044–MAX11046
ADCs measure ±5V analog inputs, and the MAX11047–MAX11049
measure 0 to 5V. These ADCs also include analog input clamps
which eliminate an external buffer on each channel.
DSP-BASED DIGITAL
PROCESSING ENGINE
MAX11046
16-BIT
ADC
•• Industry-leading dynamic range allows
early detection of error signals
–– 93dB SNR and -105dB THD
•• Simultaneous sampling eliminates
phase-adjust firmware requirements
–– 8, 6, or 4-channel ADC options
•• Lower system cost by as much as 15%
over competing simultaneous-sampling
ADCs
–– High-impedance input saves costly
precision op amp
–– Bipolar input eliminates level shifter
–– Single 5V voltage supply
–– 20mA surge protection
•• Eliminate external protection
components, saving space and cost
–– Integrated analog-input clamps and
small 8mm x 8mm TQFN package
provide the highest density per channel IGBT CURRENT DRIVERS
16-BIT
ADC
16-BIT
ADC
16-BIT
ADC
16-BIT
ADC
IPHASE1
IPHASE3
IPHASE2
THREE-PHASE ELECTRIC MOTOR
POSITION
ENCODER
The MAX11046 ADC simultaneously samples up to 8 analog-input channels.
104
Maxim Industrial Solutions
Motor Control
Monitoring and controlling multichannel currents and voltages
Detect errant motor shifts quickly by sampling at 1.25Msps
MAX1377/MAX1379/MAX1383
Benefits
The MAX1377/MAX1379/MAX1383 integrate a pair of successive
approximation register (SAR) ADCs that simultaneously sample a pair
of differential inputs. This design allows a voltage and current pair
to be sampled with the phase integrity between the two channels
preserved. The MAX1377 (0 to 5V), MAX1379 (0 to 10V), and
MAX1383 (±10V) sample up to 1.25Msps, allowing constant monitoring of the motor’s health at various analog-input ranges. These ADCs
communicate over a 4-wire SPI™ serial interface that saves cost and
space on the external isolation components compared to similar
high-speed ADCs with parallel interfaces.
•• Preserve phase integrity, save space
–– Simultaneous sampling on multiple
channels
–– Two differential or four single-ended
input channels
•• Simplify data transmission, save cost
and space on isolators
–– 4-wire SPI interface reduces number of
isolation components needed compared
to ADCs with parallel data interfaces
•• Monitor constantly with a fast sampling
speed
–– Dual integrated ADCs sample at up to
1.25Msps
VL
AVDD
AIN1A
AIN1B
MUX
12-BIT
SAR
ADC1
T/H
MAX1377
MAX1379
MAX1383
OUTPUT
BUFFER
DOUT1
CS
REF
SERIAL
INTERFACE
AND TIMING
REFSEL
CNVST
SCLK
A=1
RGND
INTERNAL
REFERENCE
U/B
CONTROL
LOGIC
S/D
VL
AIN2A
MUX
12-BIT
SAR
ADC2
T/H
AIN2B
SEL
AGND
OUTPUT
BUFFER
DOUT2
DGND
The MAX1377/MAX1379/MAX1383 integrate two ADCs for true simultaneous sampling.
www.digikey.com/maxim-industrial
105
Motor Control
High-accuracy motor control with encoder data interfaces
High-accuracy motor control with encoder data interfaces
Overview
The accuracy with which a motor
needs to be controlled depends on
the system requirements. In some
applications the accuracy requirements are very high, as in industrial
robotics or in bottling. A welding
robot, for example, is expected to
operate with high speed and high
precision. Similarly, the motors in a
bottling factory must be controlled
accurately so that bottles are
stopped at the right position for
filling, capping, and labeling. To
control a motor precisely, the rotor’s
speed, direction, and position have
to be determined. These can be
monitored with analog sensors like
resolvers, synchros, RVDTs, or rotary
potentiometers. High accuracy is
obtained with the use of encoders
like optical encoders and Hall-effect
sensors. Encoders provide the
controller with incremental and/or
absolute shaft-angle information.
106
A motor controller, commonly implemented algorithmically by a digital
signal processor (DSP), calculates the
rotor’s present speed and angle. It
adjusts the actuating power stages to
achieve the desired response efficiently
and optimally. This feedback control
loop requires robust and reliable
information from the sensor, typically
communicated over long cables from
the encoder to the controller.
Incremental information is typically
transmitted to the controller by
quadrature signals, i.e., two signals
phase shifted by 90°. These signals
can be in analog form (sine + cosine)
or in binary form. Absolute position
information, in contrast, is only
communicated by a serialized binary
data stream through RS-482 or RS-422.
As the working environments are
harsh, the data paths need to be
robust and reliable. EMI levels are high,
which explains the use of differential
signaling. High temperatures are
commonly encountered due to the
proximity to the motor.
Maxim’s extensive range of RS-485/
RS-422 and PROFIBUS interface
devices are targeted for these
motor-control applications. Interface
devices like the MAX14840E highspeed RS-485 transceiver exhibit the
high-signal integrity and robustness
expected for stringent safety control
and for sustaining the up-time of
large capital investments.
Maxim Industrial Solutions
Motor Control
High-accuracy motor control with encoder data interfaces
Make equipment more robust with fault-protected RS-485 transceivers
MAX13448E, MAX3440E–MAX3444E,
MAX13442E/MAX13443E/MAX13444E, MAX3430
Benefits
•• Integrated fault protection to ±80VDC
allows smaller encoder designs
–– Saves board space and cost of discrete
protection circuitry
–– High-speed RS-485 requirements are
met despite fault protection
–– Reduces field returns due to
misconnection
•• Multiple configurations increase design
flexibility
–– 3.3V/5V versions allow modern
low-voltage supplies
–– Full- and half-duplex operation covers all encoder needs
–– 250kbps and 10Mbps versions support
modern encoder speed requirements
•• ESD protection up to ±15kV (HBM)
reduces cost and size
–– Reduces the need for external ESD
protection
In applications where power and data are distributed over the same
cable, there is a potential for miswiring, cable shorts, or surges on
the communication bus. Maxim’s fault-protected RS-485 MAX13448E,
MAX3440E, MAX13442E, and MAX3430 transceiver families offer fault
protection up to ±80VDC . Reduces
external components,
saves up to 25%
board space
DE
VCC
DE
Y
DI
DI
Z
Y
D
Z
MAX13448E
DI
A
RO
B
N.C.
A
R
B
GND
RE
RE
ZENERS
POLYSWITCH
LIMITERS
Part
MAX13448E
VCC Supply (V)
Configuration
Fault Protection (V)
3.3 to 5
Full
±80
MAX3440E–MAX3444E
5
Half
±60
MAX13442E–MAX13444E
5
Half
±80
3.3
Half
±80
MAX3430
Maxim’s RS-485 family offers high levels of integration which saves board space and cost.
www.digikey.com/maxim-industrial
107
Motor Control
High-accuracy motor control with encoder data interfaces
Extend cable lengths in harsh motor-control environments with high-speed
RS-485 transceivers
MAX14840E/MAX14841E
Benefits
The MAX14840E/MAX14841E are 3.3V high-speed (40Mbps), halfduplex RS-485 transceivers ideally suited for industrial applications
where extended-cable-length communication is required. The
MAX14840E features a symmetrical fail-safe receiver and larger
receiver hysteresis. It provides improved noise rejection and
improved recovered signals in high-speed and long-cable applications. The MAX14841E has true fail-safe receiver inputs, guaranteeing a logic-high receiver output when inputs are shorted or open. The MAX14840E/MAX14841E are ideal for harsh motorcontrol environments.
•• Improve reliability during handling
and installation in environments with
high-static charge
–– Industry’s highest ESD protection
–– ±35kV Human Body Model (HBM)
–– ±20kV IEC 61000-4-2 (Air Gap)
–– ±10kV IEC 61000-4-2 (Contact)
•• Rugged performance in housings near
motors running at high temperatures
and in the harshest environments
–– Wide -40°C to +125°C operating
temperature range
•• Allow smaller encoder enclosures
–– Space-saving tiny 8-pin (3mm x 3mm)
TDFN package
VCC
MAX14840E
MAX14841E
R
RO
B
RE
SHUTDOWN
DE
DI
A
D
GND
Functional diagram of the MAX14840E/
MAX14841E transceivers.
108
Maxim Industrial Solutions
Motor Control
High-accuracy motor control with encoder data interfaces
Transceiver meets PROFIBUS DP standards and protects
against ±35kV ESD
MAX14770E
Benefits
The MAX14770E PROFIBUS DP transceiver meets strict PROFIBUS
standards with a high-output-drive differential (greater than 2.1V)
and an 8pF bus capacitance. The high-ESD protection (±35kV, HBM),
high-automotive-temperature grade, and space-saving 8-pin TQFN
package make the MAX14770E ideal for space-constrained, harsh
industrial environments.
•• Easy to connect to PROFIBUS networks
–– Meets EIA 61158-2 Type 3 PROFIBUS DP
specifications
–– -40°C to +125°C temperature range for
use in extreme conditions
•• Space saving
–– Tiny 8-pin, 3mm x 3mm TDFN package
•• Industry’s highest ESD protection
improves reliability
–– ±35kV Human Body Model (HBM)
–– ±20kV IEC 61000-4-2 (Air Gap)
–– ±10kV IEC 61000-4-2 (Contact)
RO
R
RE
A
SHUTDOWN
B
DE
DI
D
MAX14770E
Block diagram of the MAX14770E.
www.digikey.com/maxim-industrial
109
Motor Control
Recommended solutions
Recommended solutions
Part
Description
Features
Benefits
ADCs
MAX11044/45/46
MAX11047/48/49
16-bit, 4-/6-/8-channel,
simultaneous-sampling SAR ADCs
93dB SNR; -105dB THD; 0 to 5V or ±5V inputs;
parallel interface outputs, all eight data results in
250ksps; high-input impedance ( > 1MΩ)
High-impedance input saves the cost and space of
external amplifier
MAX1377/MAX1379/
MAX1383
12-bit, 1.25Msps, 4-channel,
simultaneous-sampling SAR ADCs
0 to 5V, 0 to 10V, or ±10V inputs; 70dB SNR; four
Serial interface saves cost and space on digital
single-ended or two differential inputs; SPI interface isolators
MAX11040
24-bit, 4-channel, simultaneoussampling, sigma-delta ADC
117dB SNR; 64ksps; internal reference; SPI
interface; 38-pin TSSOP package
Reduces motor-control firmware complexity;
captures accurate phase and magnitude information
on up to 32 channels
MAX11103*
12-bit, 3Msps, 2-channel SAR ADC
73dB SNR; SPI interface; high 1.7MHz full linear
bandwidth; single-channel (SOT23) and 2-channel
(µMAX®, TDFN) options
Tiny SOT23, µMAX, and TDFN packages save
space; serial interface simplifies data transmission
MAX9918/19/20
75V precision current sources
-20 to +75V input sensing range
Wide dynamic range supports wide range of motor
current-sensing applications
MAX4080/81
75V uni-/bidirectional current
sources
High-input voltage; bidirectional current source
Monitor current direction (sink or source) across a
wide input-voltage range
MAX4210
Power and current-sense amp with
fault detection and alert flag
Continuously monitors power consumption and
system current levels with report out
Integrated functionality reduces design time in
motor-control applications
MAX9943/44
High-voltage, precision, low-power
op amps
Wide 6V to 38V supply range; 2.4 MHz gain
bandwidth (GBW); withstands 40V transient on
any pin
Robust performance in harsh environmental
conditions
MAX9945
Low-noise, MOS-input, low-power
op amp
4.75V to 38V supply voltage range; low input-bias
current; low input-current noise; withstands 40V
transient on any pin
Robust performance in harsh environmental
conditions
MAX9650/51
20V high-output-drive op amps
1.3A output current drive
Reliable and robust design; improve noise immunity
in motor-control loop
Integrated precision amplifier and comparator
for small-signal detection; user-enabled, internal
adaptive peak threshold or flexible external threshold
Accurately detect position and speed of motors and
turning shafts; improve performance and reliability
in motor applications
Current-sense amplifiers
Operational amplifiers
Variable-reluctance (VR) sensor interface
MAX9924–MAX9927
Reluctance (VR or magnetic coil)
sensor interface devices
Hall-effect sensor and interface
MAX9641*
Dual Hall-effect sensor
Three programmable sampling periods (160µs,
500µs, and 50ms); adjustable threshold levels
Simplifies motor-control designs; provides system
flexibility
MAX9621
Dual, 2-wire Hall-effect sensor
interface
Monitors the status of Hall-effect sensor either
through the analog output or through the filtered
digital output
Provides system design flexibility through analog
and digital outputs
DS7505
Low-voltage, precision digital
thermometer and thermostat
±0.5°C accuracy from 0ºC to +70ºC; 1.7V to 3.7V
operation; industry-standard pinout
Industry-standard pinout allows easy accuracy
upgrade and supply voltage reduction from LM75
MAX6675
K-type thermocouple-to-digital
converter
Built-in cold-junction compensation
Simplest thermocouple interface; no external
components needed
Thermal management
(Continued on next page)
*Future part—contact factory for availability.
110
Maxim Industrial Solutions
Motor Control
Recommended solutions
Recommended solutions (continued)
Part
Description
Features
Benefits
Voltage supervisors
MAX6381
Single-voltage supervisor
Multiple threshold and timeout options
Versatile for easy design reuse; SC70 package
saves board space
MAX6495
72V overvoltage protector
Protects against transients up to 72V; small 6-pin
TDFN-EP package
Increases system reliability by preventing
component damage from high-voltage transients;
saves space; easy to use
MAX6720
Triple-voltage supervisor
Two fixed and one adjustable thresholds
Integration shrinks design size and increases
reliability compared to multiple components
MAX6746
Capacitor-adjustable watchdog timer
and reset IC
Capacitor-adjustable timing; 3µA supply current
Versatile for easy design reuse; SOT23 package
saves board space
MAX6816/17/18
Single/dual/octal switch debouncers
±15kV ESD (HBM) protection High reliability; easy to use; ESD protection makes
designs more robust
MAX14840E
High-speed RS-485 transceiver
40Mbps data rates; ±35kV (HBM) ESD tolerance;
3.3V; +125°C operating temperature; small 3mm x
3mm TQFN package
High receiver sensitivity and hysteresis extend
cable lengths in harsh motor-control environments
MAX13448E
Fault-protected RS-485 transceiver
±80V fault protected; full-duplex operation; 3V to
5.5V operation
Makes equipment more robust and tolerant to
misconnection faults
MAX14770E
PROFIBUS transceiver
±35kV (HBM) ESD protection; -40°C to +125°C
temperature range; small 3mm x 3mm TQFN
package
Industry’s highest ESD protection; makes motor
control more robust
MAX3535E Isolated RS-485 transceiver
3V to 5V operation; 2500V RMS isolation; ±15kV ESD
(HBM) protection
Simple solution for isolating data and power supply
MAX253
Transformer driver for isolated power
supply for RS-485/PROFIBUS
interfaces
Single 5V or 3.3V supply; 0.4µA low-current
shutdown mode; pin-selectable 350kHz or 200kHz
frequency; µMAX package
Simple open-loop circuit speeds power-supply
design; shortens time to market
Save cost with integrated DC-DC converters that
power directly off an industrial bus
Interface transceivers
DC-DC converters and controllers
MAX5080/81
Step-down DC-DC converters with
integrated switch
4.5V/7.5V to 40V VIN; 1.23V to 32V VOUT; switch to
pulse-skip mode at light loads; integrated high-side
switch
MAX5072
Dual-output buck or boost converter
with integrated switch
4.5V to 5.5V or 5.5V to 23V V IN; 0.8V (buck) to 28V Improves reliability with controlled inrush current,
(boost) VOUT; configure each output as buck or boost thermal shutdown, short-circuit protection
MAX15023
Wide 4.5V to 28V input, dual-output,
synchronous buck controller
4.5V to 28V VIN; VOUT = 0.6V to 0.85 x V IN; hiccup
mode
Thermal shutdown and short-circuit protection for
the system
MAX15034
Single-/dual-output synchronous
buck controller for high-current
applications
4.75V to 5.5V or 5V to 28V V IN; VOUT = 0.61V to
5.5V; 25A or 50A output
Thermal shutdown and monotonic start protect
devices; improves reliability
MAX15048/49
3-channel DC-DC controllers with
tracking/sequencing
4.7V to 23V VIN; VOUT = 0.6V to 19V; tracking across Saves space and cost by integrating three switching
the three outputs; power sequencing
controllers
FET drivers
Single/dual operation; 16ns propagation delay; high Simplify design with a very low propagation delay
sink/source current; 1.9W thermally enhanced TDFN and a thermally enhanced package
package
MOSFET/rectifier drivers
MAX15024/25 FET drivers
MAX5048
MAX5054–MAX5057
MAX5078
4A to 7.6A; 12ns to 20ns; single/dual MOSFET
drivers
Increase flexibility with inverting/noninverting
inputs to control the MOSFET
For a list of Maxim’s recommended motor-drive solutions, please go to: www.maxim-ic.com/motordrive.
www.digikey.com/maxim-industrial
111
Motor Control
Recommended solutions
112
Maxim Industrial Solutions
Security and
surveillance
Security and surveillance
Digital video recorders (DVRs)
Digital video recorders (DVRs)
Overview
Analog CCTV security systems are moving to digital technology, and
video recording is leading this
transition. The analog VCR has
been replaced by digital video
recorders (DVRs) in security systems
that require video monitoring and
recording. DVRs now offer overwhelming advantages over analog
VCRs in security applications. Video
footage can be digitally recorded,
processed, and streamed over digital
networks at virtually any level of
image quality, including high definition (HD). Users now make use of
digital-only technologies such as
real-time analytics, scene search,
motion- and activity-detection
alarms, and remote access over
IP networks. The cost of storage
capacity on physical media such
as hard disk drives (HDDs), digital
versatile discs (DVDs), or networkattached storage (NAS) is a small
fraction of analog tape-based
recording cost. The use of digital
video recording and archiving also
offers permanent storage of video
footage with no loss of image quality
over time. All of these factors have
driven the security industry toward
adopting DVR as the standard for
video recording.
compression standards supported;
video quality of the record, stream,
and display modes; storage capacity;
and how many functions the system
can perform simultaneously.
DVR types
Video-compression
technologies
The security market has evolved
into multiple segments for DVR
systems. Embedded, hybrid, and
PC-based DVRs all require the
essential elements of video and audio
capture: analog-to-digital conversion,
compression, playback, and network
streaming. The embedded DVR is
a stand-alone piece of equipment
that accepts analog CCTV camera
inputs for compression and storage
on a local HDD. Hybrid DVRs accept
analog CCTV and IP camera inputs
as video sources. PC-based DVRs are
integrated into surveillance stations
with hardware compression add-in
cards or software compression
running on the PC. The distinguishing
features among different models are
the number of video input channels;
H.264 is the new industry standard
for video compression in security
DVRs. Prior generations used
MPEG-4 and even MJPEG for video
recording. H.264 has the advantage
of offering the highest compression
ratio, while maintaining excellent
video quality for security applications. H.264’s higher compression
ratio (up to two times better than
prior-generation technology) effectively increases storage capacity by
100%, producing smaller file sizes
and, therefore, longer recording time
on a fixed-capacity storage device.
In addition, the use of H.264 allows
high-quality images to be transmitted over networks at very low bit
rates. Security systems that involve
multiple cameras can quickly exceed
USB
PROTECTION
PPC AND PERIPHERALS
ETHERNET
HDDs
HOST BUS AND GLUE LOGIC
MEMORY
H.264 CODEC
4 D1 ENCODERS
4 CIF ENCODERS
MEMORY
H.264 CODEC
4 D1 ENCODERS
4 CIF ENCODERS
MEMORY
H.264 CODEC
4 D1 ENCODERS
4 CIF ENCODERS
MEMORY
H.264 CODEC
4 D1 ENCODERS
4 CIF ENCODERS
POWER
SUPPLY
MEMORY
H.264 CODEC
8 D1 DECODERS
MEMORY
SERIAL
INTERFACE
CLOCK
H.264 CODEC
8 D1 DECODERS
OSD
AUDIO
FPGA AND MEMORY
ANALOG AUDIO/
VIDEO FRONT-END
ANALOG AUDIO/
VIDEO FRONT-END
ANALOG AUDIO/
VIDEO FRONT-END
ANALOG AUDIO/
VIDEO FRONT-END
FPGA
AUTHENTICATION
4 A/V INPUTS
4 A/V INPUTS
4 A/V INPUTS
4 A/V INPUTS
MAXIM SOLUTION =
SPEAKER
OR
HEADPHONES
HD DISPLAY
Functional block diagram of a security DVR system. For a list of Maxim's recommended solutions for security DVR designs, please go to: www.maxim-ic.com/DVR.
www.digikey.com/maxim-industrial
115
Security and surveillance
Digital video recorders (DVRs)
the available network bandwidth
without efficient compression. DVR
system designs without H.264 often
rely on reduced-frame-rate or lower
resolution recording techniques that
degrade picture quality in order to
increase recording time and reduce
video bit rates. Older codec formats
(MPEG-4 and MJPEG) are often still required for legacy support, but the industry’s trend to adopt H.264 as the primary codec in DVR is well
under way. Maxim’s family of H.264 processors supports MJPEG recording
and playback for backward compatibility with prior-generation equipment.
DVR system requirements
Security video applications are
moving to higher recording and
display resolutions. CIF resolution
recording (NTSC 360 x 240) was used
extensively in early generation DVRs
to produce digital video quality
comparable to the analog VCR that
it replaced. Low-resolution CIF was
also well suited to first-generation
codec technology (MJPEG/MPEG-4)
that cannot produce acceptable
compression ratios at higher resolutions. The market requirement today
and moving forward is standarddefinition (D1 NTSC 720 x 480) or
“DVD-quality” video recording.
Standard definition (SD) represents
a fourfold performance increase
in system processing power per
channel as compared to CIF. Stateof-the-art H.264 codec technology is
used at D1 resolution and above to
ensure efficient compression ratios.
Maxim’s family of H.264 processors
allows programmable video resolutions for recording at any level of
quality required.
Another trend in security and surveillance video is the requirement for
full-frame-rate video recording
and storage. Full frame rate for an
analog CCTV camera is 30 framesper-second (fps) in NTSC and 25fps in
PAL. Real-time video recording represents a twofold to fourfold increase
in processing power required per
channel versus DVR designs that
record at reduced frame rates such as
7.5fps (25% in NTSC) or 15fps (50% in
NTSC). A powerful, scalable system
architecture is required to meet the
processing requirements of new
DVR designs.
Many video security systems today
are hybrid designs of analog CCTV
equipment and digital network
technologies that have built up over
time. Preexisting digital equipment
based on older codec technologies
(MJPEG/MPEG-4) creates the need
for transcoding between formats in
new equipment. For example, the
video from an existing IP camera
with MJPEG compression must be
re-encoded to H.264 in the DVR
for efficient storage and network
bandwidth usage. DVR designs today
must accommodate multiformat
digital video input (MJPEG/MPEG-4/
H.264) to preserve investments made
in earlier generation equipment.
Maxim’s family of H.264 processors
supports video decoding in MJPEG
and MPEG2, prior to re-encoding to
H.264, for recording and streaming.
www.maxim-ic.com/DVR
116
Maxim Industrial Solutions
Security and surveillance
Digital video recorders (DVRs)
H.264 video codec system-on-a-chip (SoC) simplifies multichannel DVR system designs
while providing excellent video quality
MG3500
Benefits
The MG3500 is a highly integrated, HD or multichannel SD, H.264
codec SoC ideally suited for the security DVR market. It offers a
fully compliant baseline, main, and high-profile HD H.264 codec;
MJPEG codec; video preprocessors and postprocessors for scaling
and compositing; 240MHz ARM9™ CPU; and a host of peripherals
including Gigabit Ethernet MAC, USB OTG, SD™ card, CompactFlash®
memory, IDE, CE-ATA, SDIO, and MMC.
•• Superb video-quality recordings at any
resolution for improved identification
–– High, main, and baseline profile H.264
video codec
–– Flexible recording resolution up to 1920 x 1080i (p30)
–– Fully programmable video resolutions
and frame rates
•• Simplified multichannel system design
lowers design cost
–– 4 D1 + 4 CIF encoders per MG3500 in
encoding path
–– Simultaneous primary (recording) and
secondary (streaming) channel encoding
–– 8 D1 decoders per MG3500 in playback
decoding path
•• Integrated on-chip peripherals reduce
board size and manufacturing cost
–– 10/100/Gigabit Ethernet MAC
–– USB On-The-Go
–– NAND/NOR/SD/SDIO/MMC/CF/CE-ATA/IDE
interfaces
(Continued on next page)
MASTER/SLAVE HOST I/F
NAND/NOR/CF/IDE
16 DATA, 23 ADDRESS
MG3500
SDRAM
DDR2
1 OR 2 CHIPS
HIGH-SPEED BITSTREAM
SDRAM
CONTROLLER
SLAVE HOST/
BRIDGE
BITSTREAM I/F
AES/SHA
VOP
HD/SD
VIDEO I/O
ITU-R BT.1120 OR
ITU-R BT.656 (2x)
VIDEO INPUT
ITU-R BT.1120 OR
ITU-R BT.656 (2x)
2 STEREO
INPUTS
3 STEREO
OUTPUTS
AUDIO
ADCs AND
DACs
SD/MMC
CONTROLLER
SDIO/MMC/
CE_ATA
ARM926™
HD H.264 CODEC
HD MPEG-2 DECODER
HD JPEG CODEC
VIP-1
HD/SD
VIP-2
HD/SD
VIDEO MME
I2S
AUDIO/SYSTEM MME
CLOCKS
XTAL
MASTER HOST
ETHERNET MAC
ETHERNET
PHY
USB
WITH PHY
HI-SPEED USB
PWM
PWM (3x)
SERIAL I/O
UART (2x)
SERIAL I/O
TWI/SPI™ (2x)
ETHERNET
10/100/GigE
JTAG
MG3500 functional block diagram
www.digikey.com/maxim-industrial
117
Security and surveillance
Digital video recorders (DVRs)
H.264 video codec system-on-a-chip (SoC) simplifies multichannel DVR system designs
while providing excellent video quality (continued)
Benefits (continued)
•• Lowest power consumption per video channel in the industry
reduces heat buildup and overall operating cost
–– 500mW total power consumption
•• Complete development environment drastically reduces time
to market
–– Hardware evaluation boards available
–– Includes predeveloped software: Linux® operating system,
firmware, drivers
118
Maxim Industrial Solutions
Security and surveillance
Digital video recorders (DVRs)
Video decoder provides superior video quality
MAX9526
Benefits
The MAX9526 low-power video decoder was designed to support
multiple video (NTSC/PAL) standards, making it ideal for security and surveillance systems. It integrates true 10-bit processing, 54MHz
sampling (4x oversampling), anti-aliasing filtering, DC restoration,
automatic gain control (AGC), and 2:1 input multiplexing into a
compact, high-performance package capable of operating in a
variety of security system environments.
•• Provides superior video quality for
improved identification
–– True 10-bit decoding
–– 54MHz sampling (4x oversampling)
•• Low power consumption reduces
heat buildup and operating costs for
compact designs and portable/battery
backup
•• Programmable configuration eases
design and time to market
–– Only 16 registers required for full configurability and status indicators
•• Flexibility of operation allows one
design to serve multiple markets
–– Widest temperature range (-40°C to
+125°C) for the harshest environments
–– 1.8V/3.3V (typ) digital I/O supply voltage
–– Supports multiple analog video
standards for compatibility with a
variety of video inputs
•• Simple design speeds time to market
–– 1.8V operation
–– Integrated functionality results in few
external components, so physical design
is smaller and less prone to error
AGC
I2C AND LOGIC
DC
RESTORE
10-BIT
ADC
Y
PROC
C
PROC
OUTPUT
FORMATTER
STANDARD
ANALOG
VIDEO INPUT
Y/C
SEPARATION
MAX9526
INDUSTRY-STANDARD,
DIGITAL COMPONENT
VIDEO OUTPUT
(ITU-R BT.656) FOR
DIGITAL PROCESSING
PLL
MAX9526 digital output processing
www.digikey.com/maxim-industrial
119
Security and surveillance
Digital video recorders (DVRs)
Recommended solutions
Part
Description
Features
Benefits
Video codec
MG3500
H.264 video codec SoC
Video formats: HD 1080p30 H.264 codec, MJPEG
codec; audio formats: AAC, AMR, Dolby ®, G.7xx,
MP1/2/3; HD MPEG-2 decoder, 4 D1 + 4 CIF H.264
encoders or 8 D1 H.264 decoders
Superb video-quality recordings at any resolution
for improved identification; complete development
environment drastically reduces time to market
Low-power, high-performance NTSC/
PAL video decoder
Supports all NTSC and PAL standards; true 10-bit
digital processing; 2:1 video input mux
Superior video quality provides improved
identification; configuration method speeds design
time
MAX9652–54
3.3V, HD/SD triple-channel filter
amplifiers with shutdown
2V/V gain; 42MHz passband for HD with 50dB
attenuation at 109MHz
Allow design flexibility where switchable HD/SD
operation is required; shutdown mode saves power
MAX9586–89
Single/dual/triple/quad, SD video
Low power; small size; 8.5MHz passband; 55dB
filter amplifiers with AC-coupled input attenuation at 27MHz
buffers
Integrated solution saves PCB area
MAX9507
1.8V, DirectDrive ® video filter
amplifier with load detection and dual
SPST analog switches
Dual SPST analog switches controlled through I2C
interface; DirectDrive sets video-output level near
ground; internal gain of 8V/V; load detection and
reporting
Integrated switching functionality simplifies design;
DirectDrive eliminates output capacitance, thus
reducing cost and saving space
16-bit audio voice codec
Ultra-low power, mono codec; programmable digital
filter
Complete audio solution saves development time
MAX8654
Step-down switching regulator
25mΩ RON; 8A internal switch; 4.5V to 14V input;
6mm x 6mm, 36-pin TQFN
Reduces space requirements when implementing
power supplies requiring a high-current output
MAX15035
Step-down regulator
Fully integrated; 4V to 26V
Compact solution for small form-factor applications
MAX1970
Dual step-down converter
2.6V to 5.5V input; 750mA output current; power-on
reset (POR); 180° out-of-phase operation
Saves space by reducing input capacitance
Video decoder
MAX9526
Video amplifiers
Audio codec/DAC
MAX9860
Power ICs
USB ESD-protection IC
MAX4987
Overvoltage-protection controller with
USB ESD protection
Integrated low-RON (100mΩ) nFET switch; overcurrent Provides ESD protection for Hi-Speed USB I/O,
protection (autoretry); 1.5A (min) internal overcurrent increasing system reliability
protection
USB current-limited switch
MAX8586
USB current-limit switch
3mm x 3mm; 2.7V to 5.5V; 20ms fault blanking
Protects against power faults, increasing system
reliability while saving space
DS28E01-02
1-Wire ® SHA-1 bidirectional
authenticator with 1Kb of EEPROM
Single, dedicated contact operation; SHA-1 secure
authentication and data protection; 1Kb of EEPROM
Crypto-secure to prevent copying of FPGA design;
single FPGA I/O pin for operation
DS28E10*
1-Wire SHA-1 authenticator with 224b of Single-contact operation; unidirectional SHA-1
one-time programmable (OTP) EPROM authentication
FPGA authenticators
Lowest cost solution for SHA-1 authenticator
(Continued on next page)
* Future product—contact factory for availability.
120
Maxim Industrial Solutions
Security and surveillance
Digital video recorders (DVRs)
Recommended solutions (continued)
Part
Description
Features
Benefits
RTCs
DS1315
Phantom time chip
Real-time clock (RTC); nonvolatile memory controller
Integrated clock and memory controller save space
and provide design flexibility; phantom interface
allows communication over parallel bus with no
address space requirements
DS1500
Watchdog timekeeper with nonvolatile
memory control
Programmable watchdog timer; time-of-day alarm;
power-control circuitry
Integrated clock and memory controller save space
DS1685
Multiplexed-interface real-time clock
64-bit unique serial number; 242 bytes of batterybacked NV SRAM
Simplifies adding a unique ID to a design while
providing extra battery-backed memory
MAX6381–90
Single-voltage monitors
Low power; SC70; various reset thresholds and
timeouts
Save space, save power, and increase reliability
with no external components
MAX6443–52
Voltage monitors with extended setup
delay pushbutton
Extended pushbutton setup delay (6 seconds); manual Increases reliability by avoiding accidental resets;
reset
increases performance by allowing system to be
reset by external pushbutton
MAX16056–59
Ultra-low-power reset + watchdog ICs
125nA supply current; capacitor-adjustable reset;
watchdog timeout delays
Supervisory ICs
Save power and battery life; use one IC across
multiple applications with adjustable timeouts
For a list of Maxim's recommended solutions for security DVR designs, please go to www.maxim-ic.com/DVR.
www.digikey.com/maxim-industrial
121
Security and surveillance
Digital video recorders (DVRs)
122
Maxim Industrial Solutions
Security and surveillance
IP cameras
IP cameras
Overview
Low-power camera designs can be
powered over Ethernet (PoE) without
additional power sources. By using the
same cable to transmit both data and
power, PoE installations can substantially reduce cabling costs. In some
cases, wireless networks such as Wi-Fi®
can be used to replace Ethernet, thus
easing camera placement. This is especially true of home security cameras
where Ethernet wiring may not be
readily available, and where “cloud
computing” DVR applications replace
physical DVRs.
IP cameras use the Internet protocol
(IP) to transmit audio and video data,
along with control signals, over
Ethernet links in closed-circuit television (CCTV) systems. They offer
numerous advantages over traditional
analog security cameras, which
typically transmit an analog NTSC/PAL
signal over coaxial cable. Unlike analog
cameras, IP cameras support high-
definition (HD) images, intelligent
analytics, local video storage, and
remote control.
Multistream H.264 and
Motion-JPEG compression
Video compression is performed in
the IP camera together with analytic
functions, video encryption (to stop
hackers), and encapsulation of video
data into Ethernet packets. The
compressed video stream is usually
sent to a hybrid digital video recorder
(DVR) or network video recorder
(NVR) for storage, playback, and
display. The use of an IP network for
video monitoring can enable security
staff to be located at geographically
remote locations, allowing centralized control over security cameras
across campuses or multiple sites
using pan-tilt-zoom (PTZ) commands
sent over the IP network. The H.264 video compression
standard provides approximately
twice the compression of the
previous MPEG-4 standard for the
same video quality. Within the
H.264 standard, the “high” profile
defines the highest video quality
with the lowest bit rate, making it
especially relevant for applications
such as video security. Achieving
very-low-latency (delay) encoding
minimizes the response time from
security personnel. Meanwhile, highdefinition video encoding enables
the IP camera to capture details such
MICROPHONE
ADC/DAC
128MB DDR2
COMPOSITE
ETHERNET
POWER
SUPPLY
10/100
ETH PHY
PoE
POWER
SUPPLY
POWER
SUPPLY
CMOS
SENSOR
VIDEO
DECODER
H.264
CODEC
SoC
CONFIG
SWITCH
UART
XCVR
UART
SPEAKER
VIDEO
ENCODER
COMPOSITE
NAND
FLASH
RTC
SUPERVISOR
TEMP SENSOR
SPEAKER
AMP
DBG
UART
GPIO
HEADER
SD CARD
SLOT
INTERFACE
PROTECTION
= MAXIM SOLUTION
USB HOST
CONNECTOR
IP camera block diagram. For a list of Maxim's recommended solutions, please visit: www.maxim-ic.com/IPcamera.
www.digikey.com/maxim-industrial
Mobicam3 720p H.264/M-JPEG IP camera reference design
as facial features and license plates
for enhanced security imaging. Since
network bandwidth may be limited,
systems can require the ability to
encode/record one HD stream over
a local area network (LAN) while
simultaneously streaming a lower
resolution feed for remote viewing
over a wide area network (WAN).
In addition to H.264, many security
systems require backward compatibility with existing equipment that
does not support H.264. The MotionJPEG (M-JPEG) standard can provide
backward compatibility in such
systems, as well as the ability to take
high-resolution lossless snapshots.
Specifically, it supports simultaneous
encoding of H.264 video for uninterrupted video recording while
capturing JPEG still images, which
may be driven by specific events.
Analytics
Video analytics is the process of
analyzing video data and making
decisions based upon it. Supporting
analytics in software within the
camera enables actions to be taken
immediately based on specific events
and without the need for inputs from
security personnel. For example, an
alarm may be sounded if the camera
detects that a person has crossed
into a secure area. Analytic functions
include motion detection, trip wire,
and image tracking. All of these
functions need to be configurable
from the PC-based security management software using an intuitive
graphical user interface (GUI).
123
Security and surveillance
IP cameras
Embedded Linux® software
and networking
IP cameras need to provide the capability for streaming video to multiple
clients. For example, Maxim’s IP
camera reference design (Mobicam3)
supports up to 16 clients and both
the real-time transport protocol (RTP)
and the real-time streaming protocol
(RTSP). The following Ethernet
protocols are also supported: HTTP,
DHCP, SMTP, TCP/IP, UDP, TFTP,
FTP, NTP, and UPnP™. Streams can
be encrypted using AES or SHA
encryption to prevent hacking or
tampering.
Mobicam3: IP camera reference design kit
Mobicam3 is a complete, copyready, IP camera reference design
kit based on Maxim’s MG2580
720p H.264/M-JPEG codec system
on a chip (SoC). The design kit
includes the camera, hardware
design files, software development
kit (SDK), and demo version of
eInfochips’ video security management software. Maxim’s SDK
provides a quick start to developing an IP camera. It gives the user
low-level firmware, Linux distribution, test applications, example
code, and development tools to
easily configure and customize a
complete product.
Key camera hardware
features
PC-based video security
management software
• Small form factor: 44mm x
100mm
• Based on the MG2580 H.264 IP
camera SoC
• Power over Ethernet (PoE)
• High-quality C-mount lens
• Local video monitor output
• Bidirectional audio
• USB and microSD™ storage
• Optional I/O board for advanced
features
• Embedded analytics
• Remote-firmware upgradeable
• Auto-iris
• Mechanical PTZ (RS-485)
The Mobicam3 reference design is
supplied with a complete PC-based
video security management demo
application for configuring and
viewing media streams from the
camera. Full binary and source
code versions of the software are
available for license from eInfochips. The application includes
the following major functions to
enable the rapid development of a
complete security system:
• Multicamera control and viewing
• Scheduled recording and
playback
• Analytics including trip wire,
motion detection, and object
tracking
• Event logging
• Snapshots and alarms
• Electronic pan-tilt-zoom (ePTZ)
control
Screenshot of the video security management software showing the multicamera decoding and configuration interface.
www.maxim-ic.com/IPcamera
124
Maxim Industrial Solutions
Security and surveillance
IP cameras
High-definition H.264 codec SoC supports multistream applications with intelligent
analytics
MG2580
Benefits
Maxim’s Mobicam3 IP camera reference design uses the MG2580
codec SoC to perform multistream H.264 compression, M-JPEG
compression, analytics, AES/SHA video encryption, and Ethernet
communication functions on a single chip. The MG2580 can
compress three H.264 streams simultaneously at CIF, D1, and 720p
resolutions. Simultaneous M-JPEG video or JPEG still-image capture is also supported.
•• Highly integrated system reduces part
count, simplifies design, and reduces
camera size
–– Integrated ARM9 CPU, Ethernet, and USB
–– Audio codecs: G.722, AMR, AAC, and
MP1/2/3
–– ePTZ support
The MG2580 includes a fully programmable audio processor and
offers support for full-duplex G.722/AAC audio with the ability to
select both sample and bit rates. The full-duplex operation enables
two-way voice communication with people at the camera location.
AES and SHA encryption are performed in dedicated hardware for
the highest performance. The ARM9™ processor in the MG2580 is not
required for audio or video encoding, allowing it to be used solely for
networking and applications.
•• Multistream, high-profile video
encoding for the highest image quality
–– High, main, and baseline H.264 1280 x
720p30 codec
–– M-JPEG codec, up to 12MP
–– Triple-stream encoding: 720p plus CIF
or D1 H.264, and M-JPEG simultaneous
encoding
•• Embedded analytics reduce software
development time
–– Motion detection
–– Trip wire
–– Image tracking
MASTER/SLAVE HOST I/F
NAND/NOR/CF/IDE
16 DATA, 23 ADDRESS
MG2580
DDR2 (2x)
SDRAM
CONTROLLER
SLAVE HOST/
BRIDGE
BIT STREAM I/F
AES/SHA
VOP
HD/SD
720p H.264 CODEC
M-JPEG CODEC
VIP-1
HD/SD
VIDEO OUTPUT
ITU-R BT.656
ETHERNET MAC
USB
WITH PHY
VIP-2
HD/SD
AUDIO
ADCs AND
DACs
SD/MMC
CONTROLLER
VIDEO MME
I2S
AUDIO/SYSTEM MME
CLOCKS
XTAL
SDIO/MMC/
CE_ATA
ARM926
VIDEO INPUT
ITU-R BT.656
STEREO
INPUTS
STEREO
OUTPUTS
MASTER HOST
ETHERNET
PHY
ETHERNET
10/100
USB 2.0
PWM
PWM (3x)
SERIAL I/O
UART (2x)
SERIAL I/O
TWI/SPI (2x)
JTAG
Functional diagram of the MG2580.
www.digikey.com/maxim-industrial
125
Security and surveillance
IP cameras
Recommended solutions
Part
Description
Features
Benefits
Video codec
MG2580
H.264 HD codec SoC
H.264 and M-JPEG encoding, ARM9 processor,
Ethernet, USB, audio codecs (G.722, AMR, AAC,
MP1/2/3)
Highly integrated system reduces part count,
simplifies design, and reduces camera size
Low-power, high-performance NTSC/
PAL video decoder
Supports all NTSC and PAL standards, true 10-bit
digital processing, 2:1 video input multiplexer
Easy to configure yet flexible for multiple modes of
operation
MAX9860
16-bit mono audio codec
1.8V single-supply operation, mono codec with
programmable digital filter
Provides a complete audio solution in a small 4mm x
4mm TQFN package
MAX9718
Low-cost, mono, 1.4W differential
audio power amplifier
Class AB gives superior THD+N down to 0.002%
Simple, high-fidelity solution
ESD-protection arrays for high-speed
data interfaces
Low (5pF) capacitance; 2-, 3-, 4-, and 6-channel
options; ±15kV ESD protection
Tiny UCSP™ and WLP packages save space
Single USB switch with autoreset and
fault blanking
3mm x 3mm package, 2.7V to 5.5V supply
Selectable active-high/active-low control logic and
shutdown control provide design flexibility for use in
many designs
MAX5941/
MAX5942
IEEE � 802.3af-compliant PoE
interface/PWM controllers for
powered devices (PDs)
Single-chip solutions integrate 802.3af PD interface
and PWM; adjustable UVLO allows operation with
legacy PSE systems; surface-mount, 16-pin SO
package
802.3af-compliant PoE power supplies are highly
integrated, minimizing required space while reducing
build cost
MAX5969A/
MAX5969B
IEEE 802.3af/at-compliant PD
interface controllers with integrated
power MOSFET
IEEE 802.3af/at compliant; 100V absolute maximum
rating; simplified wall-adapter interface; thermally
enhanced, 3mm x 3mm, 10-pin TDFN
Simplify design of PDs that draw power from either a
PoE cable or a wall adapter
MAX15000/
MAX15001
Current-mode PWM controllers with
programmable switching frequency
Programmable switching frequency up to 625kHz;
digital soft-start eliminates output-voltage overshoot
and guarantees monotonic rise during power-up;
10-pin µMAX� package
Enable the implementation of very small power
supplies for PoE
MAX8667
4-channel PMIC with two step-down
converters and two low-input LDOs
2.6V to 5.5V supply, 1.2A and 600mA step-down
DC-DCs, 3mm x 3mm TQFN, 1.5MHz switching
frequency
High frequency allows for tiny external components,
thereby reducing overall power-supply size
MAX15022
Dual switching DC-DC converter with
dual LDO
500kHz to 4MHz switching frequency, 180° out-ofphase operation, 5mm x 5mm 28-pin TQFN
Simplifies design, saves space, and reduces cost
MAX8635
Dual 300mA LDO
Independent shutdown, low 90mV dropout at 100mA
load
Pin-programmable output voltage makes
configuration easy while providing flexibility for use
across many designs
Video decoder
MAX9526
Audio amplifiers
Interface protection
ESD protectors
MAX3203E–
MAX3206E
Current-limited USB switch
MAX1946
PoE controllers
Power ICs
(Continued on next page)
126
Maxim Industrial Solutions
Security and surveillance
IP cameras
Recommended solutions (continued)
Part
Description
Features
Benefits
Real-time clocks (RTCs)
DS1340
I2C RTC with trickle charger
Automatic backup power switching
DS1390
Low-voltage SPI™/3-wire RTC with
trickle charger
Automatic backup power switching, time-of-day alarm Reliable timekeeping during power-supply
interruptions
DS1318
44-bit binary counter
Resolution of 244µs; counter can be configured as an
event counter or RTC
Reliable event tracking during power-supply
interruptions
MAX6736–
MAX6745
Dual-/triple-voltage monitors
SC70 package, 6µA supply current
Conserve battery life; save board space compared to
using multiple single-voltage monitors
MAX6381–
MAX6390
Single-/dual-voltage monitors
1.8V to 5V supply, 3µA (typ) at 1.8V, SC70, various
reset thresholds and timeouts
SC70 package saves board space; no external
resistors or capacitors required
MAX16056–
MAX16059
Ultra-low-power reset + watchdog ICs 125nA supply current, capacitor-adjustable reset and
watchdog timeout delays
MAX16054
Pushbutton on/off controller
±15kV ESD protection, SOT23 package, 7µA quiescent ESD protection increases reliability; SOT23 package
current
saves board space
MAX6443–
MAX6452
Voltage monitors with extendedsetup-delay pushbutton
Extended pushbutton setup delay (6s), single or dual
manual-reset inputs
Increase reliability by avoiding accidental resets
1.8V to 5.5V operation, 13µA (max) supply current,
SC70 package
Provides temperature sensing while minimizing
power drain
Reliable timekeeping during power-supply
interruptions
Supervisors
Save power and battery life; adjustable timeouts
allow designers to use one IC across multiple
applications
Temperature sensors
MAX6613
Low-voltage analog temperature
sensor
MAX6631
Low-power digital temperature sensor ±1°C accuracy from 0°C to +70°C, 50µA (max) supply Minimizes power consumption
current
DS7505
Low-voltage, ±0.5°C accurate digital
thermometer and thermostat
±0.5°C accuracy from 0°C to +70°C, 1.7V to 3.7V
operation, industry-standard pinout and registers
Industry-standard pinout allows easy accuracy
upgrade and supply voltage reduction from LM75
For a list of Maxim's recommended solutions, please visit: www.maxim-ic.com/IPcamera.
www.digikey.com/maxim-industrial
127
Security and surveillance
IP cameras
128
Maxim Industrial Solutions
LED lighting
Lighting
LED lighting
LED lighting
The expanding role for
LED lighting
Light-emitting diodes (LEDs) are a
rapidly evolving technology and
are becoming viable for many
general lighting applications, usually
referred to as solid-state lighting.
The most relevant examples of LED
lighting applications are indoor
uses in commercial, industrial, and
residential environments; outdoor
applications like street lights and
parking lights; and architectural and
decorative lighting where LEDs were
initially adopted because of their
ability to emit the whole spectrum of colors.
LEDs have been an effective solution
for architectural lighting for some
time. Today LEDs are penetrating the mainstream general lighting
market, thanks to their higher
performance compared to other
lighting technologies:
• They have a much longer
lifetime than other lighting
technologies. LEDs can operate
for 50,000 hours versus 1,000
to 2,000 hours for incandescent
lamps and about 5,000 to 10,000
hours for compact fluorescent
lights (CFLs). This markedly longer
lifetime makes LEDs ideal for many
commercial and industrial lighting
applications where the labor cost
to replace a lamp is high.
• Their energy efficiency is
superior to incandescent and
halogen lamps, and often
equivalent to fluorescent lamps.
Additionally, the efficacy of LEDs
is continuously improving; the
efficacy of white LEDs (WLEDs)
is now forecasted to improve by
about 50% over the next three to
four years.
www.digikey.com/maxim-industrial
• They have a small form factor.
LEDs fit in some form factors like
MR16 and GU10 lamps where CFLs
do not.
• They can be dimmed with the
appropriate driver. Fluorescent
lamps pose technical limitations
when the application requires
dimming. Although conventional
LED designs have encountered
similar issues, innovative LED
drivers from Maxim are compatible with triac and trailing-edge
dimmers.
• They emit a very directional
light. Unlike other lighting technologies, LEDs are more appropriate
for applications like narrow-angle
reflector lamps that require a very
directional light.
These LED lamps must fit in the
existing form factor and be compatible with the existing infrastructure.
LEDs for remote-controlled lighting
allow greater flexibility in dimming
and changing the color of the light.
Moreover, the use of wireless or
powerline-communication (PLC)
remote controls facilitates even more new LED applications.
LED retrofit lamps
Many would argue that the LED
retrofit lamp market is the fastest
growing application for LED lighting
today. The reason for this fast growth
is actually quite straightforward:
these lamps do not require a new
• Their efficacy improves at lower
temperatures. The efficacy of
fluorescent lamps degrades at
lower temperatures. In contrast,
LEDs are ideal for applications with
a low ambient temperature like
refrigerator lighting.
• It is very easy to change the
color of their emitted light. This
makes RGB LEDs ideal for applications like architectural and mood
lighting where the color of the
light must change in real time.
In summary, LEDs offer many advantages over incandescent lamps and
fluorescent lamps. Consequently,
designers continue to find more
applications for LED lighting, but
that discussion could consume us
for a long while. This review will
focus on only two, but quite timely,
applications: LED retrofit lamps and
remote-controlled LED lighting.
LED retrofit lamps are made to
replace incandescent, halogen, or
fluorescent lamps in the same socket.
PAR20
PAR20 product photo courtesy of LEDtronics, Inc.
LuxDot™
LuxDot is a trademark of LedEngin, Inc. Photo courtesy of
LedEngin, Inc.
131
Lighting
LED lighting
electrical infrastructure (i.e., cabling, transformers, dimmers,
and sockets), a significant
advantage for LED technology.
Fitting an LED lamp into the existing
infrastructure challenges the
designer in two principal ways:
1. The form factor. Retrofit lamps
must fit in the form factor of the
previous light source.
2. Electrical compatibility.
Retrofit lamps must work
correctly and without light
flicker in the existing electrical
infrastructure.
We shall discuss each challenge in turn.
Fitting the existing form factor
The existing form factor imposes
both a physical limitation (i.e.,
the driver board has to be small
enough) and a thermal limitation
on a retrofit lamp. These limitations
pose challenges for the design of a
replacement lamp (e.g., PAR, R, and
A form factors), challenges that are
particularly hard to overcome for
smaller form factors like MR16 and GU10.
While size is important for a retrofit,
thermal limitation is often more
critical. LEDs emit only visible light;
they do not irradiate energy at
infrared wavelengths like other technologies. Thus while LEDs are more
energy efficient than incandescent or
halogen lamps, they dissipate much
more heat through thermal conduction
in the lamp.
Thermal dissipation is also the main
limiting factor for the amount of light
that a lamp can produce. Today’s
LED technology in retrofit lamps can
barely achieve a level of brightness
that is acceptable for the mainstream
market. Pushing the limits of brightness and, consequently, thermal
design are essential for designing a
commercially successful product.
132
A corollary issue to the thermal dissipation is the lifetime of the driver
board. To emit more light, the lamp
must work at a fairly high temperature (+80°C to +100°C). At these
temperatures, the lifetime of the
driver board can limit the operation
of the whole lamp. Electrolytic capacitors are, in particular, the biggest
challenge. Since they dry quickly at
those temperatures, the operation
of those capacitors is limited to no
more than a few thousand hours, and
this becomes the limiting factor for
the whole lamp. Since longevity is
a major selling point for LED lamps,
managing the relatively short lifetime
of electrolytic capacitors is a major
issue for the lamp designer.
dimmer. Triac dimmers are designed
to work well with incandescent and
halogen lamps, which are perfectly
resistive loads. With LED retrofit
lamps, however, the LED driver is
generally a very nonlinear and not
purely resistive load; its input bridge
rectifier typically draws brief, highintensity peaks of current when the
AC input voltage is at its positive and
negative peaks. This LED behavior
does not allow the triac dimmer to
work properly, because it provides
neither the needed start current
nor the hold current. As a result, the
dimmer does not start properly or
turns off while operating, and the
LED lamp light flickers in an unacceptable way.
Maxim has developed unique LED
solutions for both 120VAC/230VAC
input and 12VAC input retrofit
lamps. These LED solutions do not
require electrolytic capacitors on
the board. This extends the lifetime
of the lamp from typically less than
10,000 hours to up to 90,000 hours.
Not having electrolytic capacitors
also reduces the size of the solution,
so the driver board fits the small
retrofit form factor.
The electrical infrastructure is even
more complicated for 12VAC input
lamps, because an electronic transformer and trailing-edge dimmer
can be connected at the lamp’s input.
Again, a 12VAC input lamp driver that
uses the traditional bridge rectifier
and DC-DC converter topology
flickers because of incompatibility
with the transformer and dimmer.
Maxim’s LED solutions for 120VAC/
230VAC and 12VAC input lamps use a
single-stage conversion. By shaping
the input current so that the light
does not flicker even when dimmed,
these solutions are compatible with
triac and trailing-edge dimmers
and electronic transformers. No
other solutions for MR16 lights offer
this feature; few solutions for PAR,
R, and A lamps offer it. In addition,
these solutions provide better
Matching the electrical
infrastructure
Retrofit LED lamps must work
correctly in infrastructures that
include cut-angle (triac or trailingedge) dimmers and electronic
transformers.
Working off the 120VAC/230VAC line,
the lamp can be preceded by a triac
AC SUPPLY
120VAC/230VAC
AC SUPPLY
ELECTRONIC
TRANSFORMER
LEDs
12VAC
LED DRIVER
LEDs
120VAC/230VAC
LED DRIVER
= MAXIM SOLUTION
Block diagram for MR16 (top) and offline (bottom) lamps.
For a list of Maxim's recommended LED-lighting solutions, please go to: www.maxim-ic.com/lighting.
Maxim Industrial Solutions
Lighting
LED lighting
than 0.9 power-factor correction
and require a very limited number
of external components. No electrolytic capacitors are required,
which considerably extends the
lifetime of the driver circuit working
in a hot environment. Both the
120VAC/230VAC and 12VAC solutions
employ the MAX16834 IC, and are
available for evaluation and use in
mass production. They are both
proprietary to Maxim, which is the
only supplier to provide this combination of advantages.
Remote-controlled
applications in street,
parking, and indoor lights
with a wireless link, or they can be
controlled through existing power
lines using PLC technology.
an indoor residential application,
something in the range of 30m is
sufficient. Street lighting can require
a range of several kilometers.
PLC technology allows communication over a long range, but this can
be problematic when breakers or
transformers on the AC line do not
allow the communication to flow
freely. While wireless communications do not have this problem, the
wireless communication range can be
limited if free bands are used. A mix
of both technologies can sometimes
be the best solution: powerline
connections for devices that are
not separated by transformers, and
wireless connections to bypass
transformers.
• Low power consumption. An
important selling point of LEDs
is their high energy efficiency.
It is important that an LED lamp
consume the least power possible
when the light is off and only the
communication circuit is active.
• The communication rate. Some
lighting applications require only a
low communication bit rate (i.e., a
few kbps) to control light dimming
and perhaps read possible faults.
Architectural lighting, however,
can sometimes require a high data
rate, even 100kbps. An example
can be a wall-washer application
where many lights are controlled
through a single bus and the colors
change continuously.
The main design requirements for
remote-controlled LED lighting
solutions are:
• The communication range, which
is dictated by the application. For
As stated above, LEDs offer more
design flexibility for dimming and changing the light color. This
versatility makes them ideal for
applications like architectural
lighting, indoor ambient lighting,
and dimmable, energy-efficient
street and outdoor lighting. All these
applications require a technology to
control the LED light remotely. For
the application to be successful in the
marketplace, the cost of upgrading
the lighting infrastructure to new LED
technology must be minimized. Not
surprising, solutions that can reuse
the present infrastructure will likely be
the first to penetrate the market.
When converting to remotecontrolled LED lighting, the most
costly infrastructure upgrade to anticipate is the wiring to control the LED
lights. Fortunately, two technologies
can negate the need for that costly
upgrade: LED lamps can be controlled
www.digikey.com/maxim-industrial
AC-DC POWER
SUPPLY
ANTENNA
WIRELESS
DOWNCONVERTER/
RECEIVER
LDO
BASEBAND DIGITAL
COMMUNICATION
PWM DIMMING
= MAXIM SOLUTION
MICROCONTROLLER
LED CURRENT CONTROL
FAULT DETECTION
LEDs
LED DRIVER
Block diagram of a typical wireless-controlled lighting system.
AC-DC
CONVERTER
12V/24V/48V SUPPLY
LDO
TRANSFORMER
AC SUPPLY
= MAXIM SOLUTION
LINE
DRIVER
ANALOG
FRONTEND
1.8V/3.3V/5V
SUPPLY
LED CURRENT CONTROL
BASEBAND CHIP/
PWM DIMMING
MICROCONTROLLER FAULT DETECTION
LEDs
LED DRIVER
Block diagram of a typical PLC-controlled lighting system.
For a list of Maxim's recommended LED-lighting solutions, please go to: www.maxim-ic.com/lighting.
133
Lighting
LED lighting
• Low costs. This is true for most
lighting applications.
A remote-controlled lamp often
includes a microcontroller, either as
a discrete component or integrated
in another IC. Unless a complex
communication protocol is adopted
with a complex stack (e.g., ZigBee®),
a basic microcontroller is typically
sufficient. The microcontroller’s
duties will typically include decoding
of the communication protocol,
generation of dimming signals for
the LED driver, reading faults, and
controlling the lighting effects of the
lamp (e.g., theater dimming).
For wireless communication in
lighting applications, Maxim offers
the MAX1473 receiver and the
MAX1472 transmitter. These products
allow communication in the 300MHz
to 450MHz free bands, over a range
of 30m to 50m in an indoor environment. The MAXQ610 microcontroller
offers all the required features at a
low cost.
ting data over distances up to 10km and at data rates up to 100kbps. This range makes the parts ideal for street-lighting applications. A microcontroller with PWM outputs to control the PWM dimming input of
the LED driver is integrated into the
MAX2990. This feature eliminates the
need for another circuit to generate
this signal.
For PLC, Maxim’s solution includes
the MAX2991 analog front-end (AFE)
and the MAX2990 baseband
processor. These devices form a
powerline transmitter/receiver
chipset that is capable of transmit-
www.maxim-ic.com/lighting
134
Maxim Industrial Solutions
Lighting
LED lighting
Industrial-grade LED drivers reduce external component count
MAX16822/MAX16832
Benefits
The MAX16822/MAX16832 are high-input-voltage, buck-mode,
high-brightness (HB) LED drivers for up to 1A or 500mA current. With
hysteretic control of the LED current, they do not need a compensation circuit. They require very few external components, thus reducing
BOM cost and board area substantially compared to other solutions.
A switching MOSFET is included, and they feature an analog dimming
input with a nonlinear behavior for thermal foldback.
•• Low external component count and low
BOM cost
–– Hysteretic current control eliminates the
need for external compensation
–– Integrated switching MOSFET: up to
1A (MAX16832) or 500mA (MAX16822)
output current
–– Low 1µF input capacitor
•• Industrial-grade devices, ideal for
rough environments
–– 6.5V to 65V input range is compatible
with 12V/24V/48V inputs, and robust for
input voltage spikes
–– -40°C to +125°C operating temperature
range
–– High-power-dissipation capability in
an 8-pin SO-EP package (MAX16832)
for environments with high ambient
temperatures
–– Thermal-foldback input protects LEDs in case of overheating
VIN
RSENSE
L
CIN
TEMP_I
CS
IN
GND
PGND
MAX16822
MAX16832
DIM
LX
LX
Typical operating circuit for the MAX16822/MAX16832.
www.digikey.com/maxim-industrial
135
Lighting
LED lighting
HB LED drivers reduce BOM cost
MAX16819/MAX16820
Benefits
The MAX16819/MAX16820 are buck-mode HB LED drivers featuring
an external switching MOSFET for applications with more than 1A
current. They provide hysteretic control of the LED current so that
they do not need a compensation circuit. They require very few
external components, are low in cost, and are available in a small
package size (3mm x 3mm). These are dependable products for the
harsh operating environment of industrial applications.
•• Low external component count and low
BOM cost
–– Hysteretic current control needs no
external compensation
–– Simple, low-cost ICs
•• Ideal for applications with a limited
board area
–– Small, 3mm x 3mm, 6-pin TDFN package
•• Industrial-grade product for harsh
operating environments
–– 4.5V to 28V input voltage range
–– -40°C to +125°C operating temperature
range
VIN
RSENSE
L
CIN
CVCC
IN
CSN
DIM
VCC
MAX16819
MAX16820
DRV
GND
Typical operating circuit for the MAX16819/MAX16820.
136
Maxim Industrial Solutions
Lighting
LED lighting
Highly flexible HB LED driver provides ideal light intensity over widely varying
ambient-light conditions
MAX16834
Benefits
The MAX16834 is a highly flexible HB LED driver that can work in
buck, buck-boost, boost, SEPIC, and flyback configurations. It uses
current-mode control of the LED current. By including a driver for a
dimming pass MOSFET, it allows a 3000:1 PWM dimming range. With
its unmatched flexibility, this driver is used for Maxim’s proprietary
solutions for MR16 and offline (PAR, R, A, GU10) retrofit lamps.
•• Ideal for environments with widely
varying ambient light
–– Wide PWM dimming ratio: up to 3000:1
ratio at 200Hz dimming frequency
•• Very flexible—a single IC can work
for many different applications, thus
reducing inventory
–– For buck-boost, boost, SEPIC, flyback,
and high-side buck configurations
–– Analog and PWM dimming inputs
–– Highly flexible, it is used for Maxim’s
MR16 and offline solutions
•• Industrial-grade product provides
a fault-safe solution for rough
environments
–– Shorted- and open-LED protection
–– -40°C to +125°C operating range
VIN
C1
L1
R1
LV
FLT
IN
NDRV
D1
LED+
C3
Q1
LEDs
UVEN
HV
C2
SC
R4
CS
ON
MAX16834
OFF
PWMDIM
R3
LED-
RT/SYNC
C5
Q2
DIMOUT
R2
VCC
C4
REF
SENSE+
OVP+
R6
CLV
R5
REFI
COMP
SGND
PGND
C7
R8
R9
R10
C6
R7
Typical operating circuit for the MAX16834.
www.digikey.com/maxim-industrial
137
Lighting
LED lighting
16-bit MAXQ® microcontroller greatly extends battery life in portable equipment
MAXQ610
Benefits
The MAXQ610 is designed for low-cost, high-performance, batterypowered applications. This 16-bit, RISC-based microcontroller has
a wide operating range (down to 1.7V) for long battery life and
ultra-low power consumption. Its anticloning features and secure
MMU enable you to protect your IP.
•• Ultra-low supply current minimizes
power consumption
–– Active mode: 3.75mA at 12MHz
–– Stop mode: 200nA (typ), 2.0µA (max)
Application partitioning
and IP protection
VDD: 1.7V to 3.6V
16-BIT MAXQ
RISC CPU
REGULATOR
VOLTAGE
MONITOR
GPIOs
16-BIT TIMER
•• Secure MMU supports multiple
privilege levels, protects code from
unauthorized access
IR TIMER
AND DRIVER
4kB ROM
SECURE MMU
CLOCK
64kB FLASH
SPI™
WATCHDOG
2kB SRAM
USART0
16-BIT TIMER
8kHz NANORING
USART1
MAXQ610
Block diagram for the MAXQ610.
138
Maxim Industrial Solutions
Lighting
LED lighting
Recommended solutions
Part
Description
Features
Benefits
LED power
MAX16822
500mA, buck, switch-mode driver with
integrated MOSFET
6.5V to 65V input; LED current thermal foldback; few
external components
Small board area; low BOM cost
MAX16832
1A, buck, switch-mode driver with
integrated MOSFET
6.5V to 65V input; LED current thermal foldback; few
external components
Small board area; high-power-dissipation
package reduces need for heatsink
MAX16820
Buck, switch-mode driver
External MOSFET; > 1A output; no compensation circuit
Flexible with few external components
MAX16834
Boost and buck-boost driver
Internal driver for PWM dimming MOSFET; analog
dimming input
3000:1 dimming range; supports multiple
topologies; ideal for triac-dimmable lighting
MAX16826
Programmable, 4-channel HB LED driver
with integrated DC-DC controller
4 channels; 4.75V to 24V input voltage; up to 300mA/
channel current capability; I2C interface
Easily controlled by a microcontroller
Low-quiescent current, high-voltage linear
regulators
Low 31µA quiescent current; wide 4V to 72V input
voltage range; active-low RESET with fixed or adjustable
thresholds; small, thermally-enhanced 1.9W, 3mm x 3mm
TDFN package
Low quiescent current improves energy
savings
Low-power, 16-bit microcontroller
1.7V to 3.6V supply range; up to 32 GPIOs; wakeup timer
Extends battery life; low cost
LDO
MAX6765–
MAX6774
Microcontroller
MAXQ610
Powerline controllers
MAX2990
10kHz to 490kHz OFDM-based PLC modem Combines the physical layer (PHY) and media access
controller (MAC) to provide a data rate of 100kbps over
the powerline
High-reliability data communications
MAX2991
Integrated AFE receiver for PLC
Optimized to operate with the MAX2990; on-chip bandselect filter, VGA, and a 10-bit ADC for the Rx path
High receiver sensitivity for long-range
communication
MAX1472
300MHz to 450MHz, low-power, crystal
based, ASK transmitter
Crystal based; low power; 3mm x 3mm package
Superior performance; long battery life;
compact
MAX1473
300MHz to 450MHz ASK receiver with
automatic gain control (AGC)
High sensitivity and AGC; 5mm x 5mm package; single
supply
Long range; low solution cost; compact
RF ICs
For a list of Maxim's recommended LED-lighting solutions, please go to: www.maxim-ic.com/lighting.
www.digikey.com/maxim-industrial
139
Lighting
LED lighting
140
Maxim Industrial Solutions
Related functions
Related functions
Trim, calibrate, and adjust
Trim, calibrate, and adjust
Making industrial equipment
accurate, safe, and affordable with electronic
calibration
We demand safety in our factories.
Customers expect quality products,
which require accurate manufacturing equipment. At the same time,
equipment must be affordable. How
can manufacturers deliver “perfect”
equipment at a reasonable price? In a
word, calibration. Electronic calibration enables the remote calibration
and testing of field devices such as
sensors, valves, and actuators. Because
field devices and programmable logic
controllers (PLCs) are size constrained,
they benefit from the small size of electronic calibration devices.
All practical components, both
mechanical and electronic, have
manufacturing tolerances. The more
relaxed the tolerance, the more
affordable the component. When
components are assembled into a
system, the individual tolerances
sum to create a total system error
tolerance. Through the proper
design of trim, adjustment, and calibration circuits, it is possible to
correct these system errors, thereby
making equipment safe, accurate, and affordable.
Calibration can reduce cost in many
areas. It can be used to remove
manufacturing tolerances, specify
less-expensive components, reduce
test time, improve reliability, increase
customer satisfaction, reduce
customer returns, lower warranty costs,
and speed product delivery.
Digitally controlled calibration
devices and potentiometers (pots)
are replacing mechanical pots in
many factory settings. This digital
approach results in better reliability
and improved employee safety. This
www.digikey.com/maxim-industrial
increased dependability can reduce
product liability concerns. Another
advantage is reduced test time and
expense by removing human error.
Automatic test equipment (ATE) can
perform the test functions quickly
and precisely, time after time. In
addition, digital devices are insensitive to dust, dirt, and moisture, which
can cause failure in mechanical pots.
Testing and calibration fall into three
broad areas: production-line final
testing, periodic self-testing, and
continuous monitoring and readjustment. Practical products may
use some or all of the above test
methods.
Compensating for component
tolerances using final-test
calibration
Final-test calibration corrects for
errors caused by the combined
tolerances of many components.
One or more adjustments may be
required to calibrate the device under test (DUT) to meet a manufacturer’s specifications.
To provide a simple example, we
will say that this equipment uses
resistors with five percent tolerance
in several circuits. In design, we
simulate the circuits and perform
Monte Carlo testing. That is, we
randomly change the resistor values
within the tolerance limits to explore
their effects on the output signal.
The simulation results in a family
of curves that show the worst-case
errors that the resistor tolerances
cause. With this knowledge, the
designer decides to use the circuits
as-is and to simply adjust the offset
and span (gain) during final test to
meet system specifications. So, we
make measurements in the final
production test and have a human
set the span and offset using two
mechanical pots. Calibration is
complete, but have we solved the
problem, masked the problem, or
added a bigger unknown?
Experienced production engineers
know human error is a real issue.
Unintentional slips can ruin the
best of plans. Asking a human to
perform a boring, repetitive task is
asking for problems. A better way is
to automate such a task. Electrically
adjustable calibration devices enable
quick automatic testing, which
improves repeatability, reduces cost,
and enhances safety by removing the
human-error factor.
Improving reliability and
long-term stability by poweron self-test and continuous/
periodic calibration
Manufacturing tolerances are
compensated for by calibration
during the final production test, and
that data is utilized when a system
is powered up. Environmental
parameters in the field also create
a need for test and calibration.
Such environmental factors include
temperature, humidity, and circuit
component aging (drift), which result
in signal span and offset errors. Some
circuits contain control or average
information, which can be periodically memorized. These factors are
accounted for with a combination of
self-test at power-up and periodic or
continuous testing. The field testing
may be as simple as sensing temperature and compensating accordingly,
or it may be more complex.
Many products include an internal
microprocessor, which can aid
testing. For example, a weight scale
can compensate for the weight of the
product package, such as a plastic
bag or glass jar. Subtracting the
weight of the package (tare weight)
143
Related functions
Trim, calibrate, and adjust
from the gross weight is necessary to
accurately measure the net weight of
the material on the scale. Because the
weight of the package may change
over time due to manufacturing
variation or a change of vendors,
it is desirable to update the tare or
container weight from time to time.
Another example is using a switch to
short an amplifier input to ground
to measure offset voltage. This could
be done during power-on self-test to
compensate for component aging.
Alternatively, it can be performed
periodically to compensate for
temperature-induced drift. If the
temperature drift is predictable and
repeatable, a microprocessor can aid
testing by measuring temperature
and controlling the calibration device
in an open-loop manner.
System gain errors can be calibrated
by switching a known signal into
the equipment at an early stage and
measuring the output level. This is
done at power-up or periodically
during lulls in operation.
Enabling accurate automated
adjustments with calibration
DACs and pots
Calibration digital-to-analog converters (CDACs) and calibration digital
pots (CDPots) share some unique
attributes that enable trimming,
adjustment, and calibration. The
first advantage is internal nonvolatile memory, which automatically
restores the calibration setting
during power-up. Figure 1 illustrates
a second advantage: the ability to
customize the calibration granularity
and location for industrial safety.
Ordinary DACs allow a single
reference voltage (VREF) to be
applied; this reference voltage
usually becomes the highest DAC
setting. The lowest DAC setting is a
fixed voltage, typically ground. For a
near-center adjustment, much of this
range between VREF and ground must
144
be ignored and not used, since the available step size is evenly distributed over the range. For example,
with VREF set to 4V, a 10-bit DAC
yields a step size of 0.0039V per step. It is critical in industrial equipment to
remove all safety-related errors.
Removing the unused adjustment
range eliminates any possibility that the
circuit could be grossly misadjusted.
The CDAC and CDPot allow both
the top and bottom DAC voltage
to be set to arbitrary voltages, thus
removing excess adjustment range.
In Figure 1, a low value of 1V and
a high value of 2V are selected as
examples. To achieve a 0.0039V step
size over the 1V to 2V range, only an
8-bit device is needed, which saves
cost. Additionally, this increases
safety by removing any possibility
that the circuit could be misadjusted.
The high and low voltages for the
CDAC are arbitrary and, therefore,
can be centered wherever the
ORDINARY DAC
circuit calibration is required. If the
tolerance analysis for the circuit
indicates that a range of 1.328V to
1.875V is needed for calibration, it
can be accommodated. The 256-step
device would yield a granularity of
0.00214V. Thus, the granularity of the
adjustment can be optimized for the
specific application.
Reducing cost and improving
accuracy by replacing
mechanical trims with allelectronic equivalents
Digitally controlled adjustable
devices offer several advantages
over mechanical devices in industrial
systems. The largest advantage is
lower cost. ATE can perform calibration precisely time after time, thereby
eliminating the considerable costs
associated with error-prone manual
adjustments. Also, digital pots allow
periodic testing to occur more
4V
REFIN
4V
10 BITS, 1024 STEPS
10-BIT
DAC
OUT
Ground
0.0039V
per step
FB
GROUND
CALIBRATION DAC
2V
2V
REFHI
8-BIT
DAC
1V
REFLO
8 BITS, 256 STEPS
OUT
1V
Figure 1. Comparing the calibration range of an ordinary DAC to a CDAC.
Maxim Industrial Solutions
Related functions
Trim, calibrate, and adjust
frequently or over longer equipment
lifespans, since they can guarantee
50,000 writing cycles. The best
mechanical pots can support only a
few thousand adjustments.
Location flexibility and size are other
advantages compared to mechanical
pots. Digitally adjustable pots can
be mounted on the circuit board
directly in the signal path, exactly
where they are needed. In contrast,
mechanical pots may require human
access, which can necessitate long
circuit traces or coaxial cables. In
sensitive circuits, the capacitance,
time delay, or interference pickup of
these cables can reduce equipment
performance.
Digital pots also maintain their
calibration values better over
time, whereas mechanical pots
can continue to experience small
movements even after they are
sealed. The wiper will move as the
wiper spring relaxes, when the pot is
temperature cycled, or when the pot
is subjected to shipping vibration.
Calibration values stored in digital pots are not affected by these factors.
A one-time programmable (OTP)
CDPot can be used for extra safety. It
permanently locks in the calibration
setting, preventing an operator
from making further adjustments.
To change the calibration value,
one must physically replace the OTP
CDPot. A special variant of the OTP
CDPot always returns to its stored
value upon power-on reset, while
allowing operators to make limited
adjustments during operation at
their discretion.
UNITS ARE
ASSEMBLED
Leveraging precision
voltage references for
digital calibration
Sensor and voltage measurements
with precision analog-to-digital
converters (ADCs) are only as good
as the voltage reference used for
comparison. Likewise, output control
signals are only as accurate as the
reference voltage supplied to the
DAC, amplifier, or cable driver.
Common power supplies are not
adequate to act as precision voltage
references. Typical power supplies
are only five to ten percent accurate;
they change with load and line
changes; and they tend to be noisy.
Compact, low-power, low-noise, and
low-temperature-coefficient voltage
references are affordable and easy
to use. In addition, some references
have internal temperature sensors to
aid in the tracking of environmental
variations.
In general, there are three kinds of
serial calibration voltage references
(CRefs), each of which offers unique
advantages for different factory
applications. Having a choice of
serial voltage references enables the
designer to optimize and calibrate his
exact circuits.
The first type of reference enables a
small trim range, typically three to six
percent; this is an advantage for gain
trim in industrial imaging systems.
For instance, coupling a video DAC
with a trimmable CRef allows the
overall system gain to be fine-tuned
by simply adjusting the CRef voltage.
TESTED UNITS ARE PLACED
INTO A HOLDING INVENTORY
CUSTOMER ORDERS 10K
1.35V VOUT SUPPLIES
The second type is an adjustable
reference that allows adjustment
over a wide range (e.g., 1V to 12V),
which is advantageous for field
devices that have wide-tolerance
sensors and that must operate on
unstable power. Portable maintenance devices may need to operate
from batteries, automotive power, or emergency power generators.
The third type, called an E2CRef, integrates memory, allowing a single-pin
command to copy any voltage
between 0.3V and [VIN - 0.3V] and,
then, to infinitely hold that level.
E2CRefs benefit test and monitoring
instruments that need to establish a
baseline or warning-alert threshold.
Figure 2 illustrates the production
advantages of using an E2CRef. In this
example, a power-supply manufacturer uses an E2CRef to create an
affordable power supply that stores
the setting established during final
production test. The manufacturer
builds a generic power supply and
places it into a holding inventory.
When a customer order is received,
the output voltage is adjusted by an
automated test system before the
order is shipped.
The power-supply manufacturer
leverages final-test calibration to
provide two real benefits. First, he
reduces cost by using individual
components with relaxed tolerances,
as the final-test calibration corrects
for cumulative errors. Second,
he provides faster delivery to the
customer by making custom adjustments to a standard product.
UNITS ARE PULLED FROM
INVENTORY AND VOUT
IS ADJUSTED
UNITS ARE IMMEDIATELY
SHIPPED TO THE CUSTOMER
Figure 2. Illustrating the manufacturing benefits of using an E2CRef.
www.digikey.com/maxim-industrial
145
Related functions
Trim, calibrate, and adjust
“Just-in-time” inventory control is
more important today than it has
ever been because getting the order
may hinge on quick delivery time.
Winning an order when a competitor fails to deliver can lead to repeat
orders. Plus, increasing inventory
turns increased profit directly to the
bottom line.
146
Summary
Calibration is a means to an end.
Practical devices have manufacturing component tolerances that
can be calibrated out during final
production test with laboratorygrade external test equipment.
Environmental drift due to time,
humidity, or temperature requires
field calibration. Electronically adjust-
able calibration parts allow quick
field calibration including power-on
self-test and continuous or periodic
calibration. Periodic calibration may
also include calibration against laboratory equipment with standards
traceable to a recognized standards
body. Electronic calibration helps us
meet our goal; it allows us to have
affordable industrial equipment that
is also safe and accurate.
Maxim Industrial Solutions
Related functions
Trim, calibrate, and adjust
Recommended solutions
Part
Description
Features
Benefits
CDPots
MAX5481
1024-tap (10-bit) CDPot with SPI™ or up/
down interface
1.0µA (max) in standby, 400µA (max) during
memory write
Minimal power use for battery-operated portable
devices
MAX5477
Dual, 256-step (8-bit) CDPot with I2C
interface
EEPROM write protection, single-supply
operation (2.7V to 5.25V)
EEPROM protection retains calibration data for
safety
MAX5422
Single, 256-step (8-bit) CDPot with SPI
interface
Tiny (3mm x 3mm) TDFN package
Saves PCB space for portable products
MAX5427
32-step (5-bit), OTP CDPot
OTP or OTP plus adjustment
Versatile, reduces component count by performing
two functions
DS3502
128-step (7-bit) CDPot with I2C interface
High output-voltage range (up to 15.5V)
Permits direct calibration of high-voltage circuits
MAX5105/MAX5115 Quad, 8-bit CDACs with independent high
and low reference inputs
Rail-to-rail output buffers, choice of I2C or
SPI interface
Selectable voltage range improves granularity and
prevents unsafe adjustments
MAX5106
Quad, 8-bit CDAC with independently
adjustable voltage ranges
Allows customization of calibration
granularity; small 5mm x 6mm package
Saves PCB space for portable products
MAX5116
Quad, 8-bit CDAC with independent high and Four amplifier circuits are calibrated by one
low reference inputs
5mm x 6mm part
MAX5109
Dual, 8-bit CDAC with independent high and
low reference inputs
Battery friendly for portable devices; custom range
Single-supply operation (2.7V to 5.25V),
and granularity control
200µA per DAC, less than 25µA in powerdown, rail-to-rail output buffers, I2C interface
DS1851
Dual temperature-controlled CDAC
Each DAC has EEPROM, which can contain
temperature coefficients for temperaturespecific calibration
System temperature effects can be corrected
without any additional external devices, thus saving
space and cost
MAX6160
Adjustable CRef (1.23V to 12.4V)
Low 200mV dropout; 75µA supply current
is virtually independent of input-voltage
variations
Longer battery life in portable equipment
MAX6037
Adjustable CRef (1.184V to 5V)
Shutdown mode (500nA, max), low 100mV
(max) dropout at 1mA load, 5-pin SOT23
(9mm 2)
Battery friendly and small size for portable
applications
MAX6173
Precise voltage reference with temperature
sensor
±0.05% (max) initial accuracy, ±3ppm/°C
(max) temperature stability
Allows analog system gain trim while maintaining
the digital accuracy of ADCs and DACs
MAX6220
Low-noise, precision voltage reference
8V to 40V input-voltage range, ultra-low
1.5µVP-P noise (0.1Hz to 10Hz)
Dependable operation from unstable power
(batteries, automotive power, or emergency power
generators)
DS4303
Electronically programmable voltage
reference
Wide, adjustable output-voltage range can
be set within 300mV of the supply rails with
±1mV accuracy
A calibration voltage is memorized forever using
one simple GPIO pin
CDACs
Reduces costs with fewer components, saves PCB
area, and simplifies control
CRefs and E2CRefs
www.digikey.com/maxim-industrial
147
Related functions
Trim, calibrate, and adjust
148
Maxim Industrial Solutions
Legal notices
Legal notices
Trademark information
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μMAX is a registered trademark of Maxim Integrated Products, Inc.
1-Wire is a registered trademark of Maxim Integrated Products, Inc.
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ARM926 is a trademark of ARM Ltd.
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CompoNet is a registered trademark of OMRON Corporation.
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EMV is a trademark owned by EMVCo LLC. (See EMV Disclaimer.*)
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Flash is a registered trademark of Adobe Systems Incorporated.
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HART is a registered trademark of the HART Communication Foundation.
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Linux is a registered trademark of Linus Torvalds.
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MICROWIRE is a trademark of National Semiconductor Corp.
Modbus is a registered trademark of Gould Inc.
NovaSensor is a registered trademark GE Infrastructure Sensing, Inc. GE is a registered trademark of General Electric Company.
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Specifications, Version 3.1.1, as of the date of testing. EMVCo approval is not in any way an endorsement or warranty regarding the completeness of the approval process or the
functionality, quality or performance of any particular product or service. EMVCo does not warrant any products or services provided by third parties, including, but not limited to, the
producer or provider of the IFM and EMVCo approval does not under any circumstances include or imply any product warranties from EMVCo, including, without limitation, any implied
warranties of merchantability, fitness for purpose, or non-infringement, all of which are expressly disclaimed by EMVCo. All rights and remedies regarding products and services which
have received EMVCo approval shall be provided by the party providing such products or services, and not by EMVCo and EMVCo accepts no liability whatsoever in connection
therewith. (www.maxim-ic.com/legal/emvco_disclaimer.cfm)
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151
Legal notices
Trademark information
Trademark information (continued)
QSPI is a trademark of Motorola, Inc.
SD is a trademark of the SD Card Association.
SMBus is a trademark of Intel Corporation.
SPI is a trademark of Motorola, Inc.
The PROFI BUS PROCESS FIELD BUS logo is a registered trademark of PROFIBUS and PROFINET International (PI).
UCSP is a trademark of Maxim Integrated Products, Inc.
UL is a registered trademark of Underwriters Laboratory, Inc.
UPnP is a trademark of the UPnP Implementers Corporation.
Wi-Fi is a registered trademark of Wireless Ethernet Compatibility Alliance, Inc.
Xilinx is a registered trademark of Xilinx, Inc.
ZigBee is a registered service mark of ZigBee Alliance Corp.
152
Maxim Industrial Solutions
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Innovation Delivered is a trademark and Maxim is a registered trademark of Maxim Integrated Products, Inc. © 2010 Maxim Integrated Products, Inc. All rights reserved.
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