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: email@example.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. www.digikey.com/maxim-industrial iii 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 www.digikey.com/maxim-industrial 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 www.digikey.com/maxim-industrial 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 www.digikey.com/maxim-industrial 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 Trademark information 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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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 www.digikey.com/maxim-industrial Innovation Delivered is a trademark and Maxim is a registered trademark of Maxim Integrated Products, Inc. © 2010 Maxim Integrated Products, Inc. All rights reserved.