NEWS BRIEFS
Volume Twenty-Seven
NEWS BRIEFS
Maxim Reports Increased Business Activity In Q397
2
IN-DEPTH ARTICLE
New developments in battery chargers
3
DESIGN SHOWCASE
Load switcher draws only 6µA
9
NEW PRODUCTS
Single-cell boost converter generates auxiliary bias for LCD
10
Supply generates 5V from solar-cell power
12
Battery-switchover circuit accommodates 3V systems
13
Off-the-shelf transformer adapts controller for SLIC applications
14
Data Converters
•
•
•
•
•
Low-power 8-bit DACs offer voltage output in a tiny package
Low-cost, 3V, multichannel 8-bit ADCs are the smallest available
5V, 12-bit/10-bit ADCs connect directly to 3V µPs
Small, low-power, 12-bit VOUT DACs have configurable outputs
10-bit serial VOUT DACs available in 8-pin µMAX
(MAX548A/549A/550A)
(MAX1110/1111)
(MAX1202/1203/1204)
(MAX5352/5353)
(MAX5354/5355)
16
16
16
17
17
(MAX965–970)
(MAX985/986/989/
990/993/994)
(MAX4119/4120)
(MAX4162/4163/4164)
(MAX4165–4169)
(MAX4180–4187)
(MAX4223–4228)
(MAX4308/4309)
(MAX4330–4334)
19
18
20
17
19
18
19
17
18
(MAX336/337)
(MAX4541–4544)
20
20
(MAX629)
(MAX679)
(MAX863)
(MAX1615)
(MAX1624/1625)
(MAX1630–1635)
22
23
21
21
22
21
(MAX3187)
23
(MAX6325/6341/6350)
23
Op Amps and Comparators
• Ultra-low-voltage micropower comparators include 1.235V ±1.5% references
• Micropower, rail-to-rail I/O comparators come in 5-pin SOT23
•
•
•
•
•
•
•
Quad, wideband current-mode amplifiers have 0.1dB gain flatness to 90MHz
SOT23 rail-to-rail I/O op amps provide 200kHz GBW at 25µA ISUPPLY
Precision, single-supply op amps have rail-to-rail I/O
Ultra-low-power amplifiers offer SOT23 packaging and Hi-Z shutdown
1GHz current-mode amplifiers offer SOT23 packaging and Hi-Z shutdown
400MHz voltage-feedback op amps have ultra-low -93dB distortion
3MHz, low-power op amps with rail-to-rail I/O available in SOT23
Analog Switches and Multiplexers
• 16-channel/dual 8-channel CMOS muxes feature ultra-low leakage
• Dual SPST/SPDT analog switch fits in 6-pin SOT23
Power-Management ICs
•
•
•
•
•
•
Step-up DC-DC converter supplies ±28V for LCDs and varactors
Boost 2-cell batteries to 3.3V; no inductor needed
Dual, step-up dc-dc controller is smallest available
Micropower linear regulator accepts inputs to 28V
High-performance step-down controllers power high-end CPUs
Multiple-output notebook power-supply controllers are 96% efficient
Interface IC
• Dual, 230kbps RS-232 serial port (6 Tx/10 Rx) withstands ±15kV ESD
Voltage References
• Low-noise, precision voltage references guarantee 1ppm/°C tempcos
News Briefs
MAXIM REPORTS INCREASED BUSINESS ACTIVITY IN Q397
Maxim Integrated Products, Inc., reported net revenues of $111 million for the third quarter of fiscal 1997
ending March 31, 1997. Net income for Q397 was $35.4 million and income per share was $0.48. Sequentially,
the results for Q397 showed an increase over Q297 net revenues of $104.7 million, net income of $33.3 million,
and earnings per share of $0.46.
During the quarter, the Company increased cash and short-term investments by $24 million after paying
$11 million for capital equipment and repurchasing $29 million of its common stock. Accounts receivable days
decreased slightly from Q297 levels. Inventory declined $1.0 million from Q297.
During Q397, backlog shippable within the next twelve months grew to $124 million from the $103
million reported at the end of Q297. Orders requested for delivery in Q497 remained high, representing 76% of
the beginning Q497 backlog.
Turns orders received in Q397 increased by more than 17% over those received in Q297 to a record $45.4
million. (Turns orders are customer orders that are for delivery within the same quarter and may result in revenue
within the quarter if the Company has available inventory that matches those orders.)
Net bookings were up 30% from Q297 levels. The Company experienced sequential quarter over quarter
growth in net bookings across all geographic regions and across all of Maxim’s business units. Customer cancellations were $12.5 million, continuing the decline experienced over the last three quarters.
Bookings for Maxim’s high-frequency products were up over 50% from last quarter. Customer inventories
of high-frequency products that hampered bookings in Q197 and Q297 appear to be returning to normal levels.
Gross margins for the third quarter of 1997 were 66.3%, compared to 66.1% in Q297. R&D expenses
increased by $1.6 million to 11.8% of net revenues due to continued investments in product development efforts.
Jack Gifford, Chairman, President and CEO, commented on the quarter: “Maxim is performing very well.
Once again we did a good job of predicting and responding to significant turns orders. We are pleased with the
sequential quarter over quarter growth in gross and net bookings across all of our business units and geographic
territories. These improved business conditions should enable us to have further sequential growth next quarter.
As of today, we have introduced twice the number of products in fiscal 1997 that we did in the comparable period
in fiscal 1996.”
Safe harbor statement under the Private Securities Litigation Reform Act of 1995: Forward-looking statements in this news release involve risk and uncertainty. Important factors, including overall economic conditions,
demand for electronic products and semiconductors generally, demand for the Company’s products in particular,
availability of raw material, equipment, supplies and services, unanticipated manufacturing problems, technological and product development risks, competitors’ actions and other risk factors described in the Company’s
filings with the Securities and Exchange Commission could cause actual results to differ materially.
MAXIM’S ENGINEERS HONORED BY EDN
Y
G
O
DR
IV
IN
G
RONIC TEC
HN
CT
O
LE
E
L
T
O
TH
E NEXT
C
U
R
Y
'96
I
N
E
N
T
R
WINNE
Congratulations to Maxim’s Dave Bingham and Charlie Allen, who have been honored
by EDN Magazine as Innovators of the Year for 1996. They were recognized for their patented
AutoShutdown/ AutoWakeup technology, which is featured in a variety of Maxim RS-232 ICs.
One of these RS-232 products, the MAX3238, was awarded EDN Innovation of the Year in the
analog IC and semiconductor category. The MAX3238 eliminates the need for shutdown
software and cuts RS-232 serial-port supply current to 1µA.
Winners of EDN’s Innovator and Innovation Awards are elected by EDN readers; these awards are a
prestigious recognition from a cross-section of design engineers.
voltage starts to drop (when ∆V/∆t becomes negative).
Otherwise, the charging current delivers excess energy,
which acts on the battery’s electrolyte to dissociate water
into hydrogen and oxygen gases. This results in a rise in
internal pressure and temperature and a decrease in terminal
voltage. If fast charging continues, the battery can vent
(explode).
New developments
in battery chargers
Electronic equipment is increasingly becoming smaller,
lighter, and more functional, thanks to the push of technological advancements and the pull from customer
demand. The result of these demands has been rapid
advances in battery technology and in the associated
circuitry for battery charging and protection.
As a secondary or backup measure, NiCd and NiMH
chargers often monitor the battery’s temperature (in
addition to its voltage) to ensure that fast charging is
terminated before the battery is damaged. Fast charging
should stop when a NiCd’s ∆V/∆t becomes negative. For
NiMH batteries, fast charging should stop when the
terminal voltage peaks (when ∆V/∆t goes to zero).
For many years, nickel-cadmium (NiCd) batteries have
been the standard for small electronic systems. A few
larger systems, such as laptop computers and high-power
radios, operated on “gel-cell” lead-acid batteries.
Eventually, the combined effects of environmental
problems and increased demand on the batteries led to the
development of new battery technologies: nickel-metal
hydride (NiMH), rechargeable alkaline, and lithium ion
(Li+). These new battery technologies require more sophisticated charging and protection circuitry.
Trickle charging is simple for NiCd and NiMH batteries.
As an alternative to fast charging, the use of a small
trickle current produces a relatively small rise in temperature that poses no threat of damage to the battery. There is
no need to terminate the trickle charge or to monitor the
battery voltage. The maximum trickle current allowed
varies with battery type and ambient temperature, but
C/15 is generally safe for typical conditions.
NiCd and NiMH batteries
NiCd has long been the preferred technology for
rechargeable batteries in portable electronic equipment,
and in some ways, NiCd batteries still outperform the
newer technologies. NiCd batteries have less capacity
than Li+ or NiMH types, but their low impedance is
attractive in applications that require high current for
short periods. Power tools, for example, will continue to
use NiCd battery packs indefinitely.
Lithium-ion batteries
The most popular innovation in battery technology over
the past few years has been the introduction of Li+
batteries. Li+ batteries have a higher capacity than other
rechargeable types now in mass production, such as NiCd
and NiMH. The advantage of Li+ over NiMH is only
10% to 30% when measuring capacity as energy per unit
volume, but volumetric capacity is not the only property
to consider; weight is also important in a portable device.
When measuring capacity as energy per unit mass, Li+
batteries are clearly superior (NiMH batteries are relatively heavy). Because they are lighter, Li+ batteries have
nearly twice as much capacity per unit mass.
Though similar to NiCd types, NiMH batteries have
greater capacity. This advantage is offset somewhat by
the NiMH battery’s higher self-discharge rate—approximately double that of the NiCd, which is relatively high
to begin with (about 1% of capacity per day). Thus,
NiMH batteries are not suitable for applications in which
the battery is expected to hold its charge for a long time.
Li+ batteries also have many limitations. They are highly
sensitive to overcharging and undercharging. You must
charge to the maximum voltage to store maximum
energy, but excessive voltage can cause permanent
damage to a Li+ battery, as can excessive charge or
discharge current. Discharging the battery also carries a
caveat: repeated discharges to a sufficiently low voltage
can cause a loss of capacity. Therefore, to protect the
battery, you must limit its current and voltage when
discharging as well as when charging. Most Li+ battery
packs include some form of undervoltage- and overvoltage-disconnect circuitry. Other typical features
include a fuse to prevent exposure to excessive current
and a switch that open circuits the battery if high pressure
causes it to vent.
NiMH batteries also differ from NiCd batteries in the
method required to fast charge them. Both types can be
fast charged with a current equal to or greater than the
capacity (C) in ampere hours. This technique allows you
to charge a battery in about an hour or less. Because of
internal losses, a battery charged at C for one hour cannot
reach full capacity. For full capacity, you must either
charge for an hour at more than C, or charge
at C for more than an hour. Charging losses vary with the
charging rate and from battery to battery.
When charging a NiCd battery, its terminal voltage peaks
and then declines as the battery reaches capacity. An
applied fast charge should therefore terminate when this
3
Unlike NiCd and NiMH batteries, which require a current
source for charging, Li+ batteries must be charged with a
combination current-and-voltage source. To achieve the
maximum charge without damage, most Li+ chargers
maintain a 1% tolerance on the output voltage. (The slight
additional capacity gained with a tighter tolerance is
generally not worth the extra difficulty and expense
required to achieve it.)
high as 2V per cell, depending on the battery’s condition
and its charging rate. The dc-source voltage must therefore
be greater than 4 x 2V = 8V. The voltage level of cells in a
fully discharged battery can measure as low as 0.9V each;
in this case, the battery voltage is 4 x 0.9V = 3.6V. If the
dc source is 8V, the pass transistor sees 8V - 3.6V = 4.4V.
When charging a fully discharged battery, the dissipated
power is 4.4W in the charger and 3.6W in the battery—
an efficiency of only 45%! The actual efficiency is even
lower, because the dc source voltage must be higher than
8V to account for dropout voltage in the pass transistor
and tolerance in the source.
For protection, a Li+ battery pack usually includes
MOSFETs that open circuit the battery in the presence of
undervoltage or overvoltage. These protection MOSFETs
also enable an alternative charging method (applying a
constant current with no voltage limit) in which the
MOSFETs are turned on and off as necessary to maintain
appropriate battery voltage. The battery’s capacitance
helps to slow the rise of battery voltage, but use caution:
battery capacitance varies widely over frequency, as well
as from battery to battery.
A linear, single-cell Li+ charger is suitable for use in a
cradle charger (Figure 1). It drives an external power
transistor (Q1) that drops the source voltage down to the
battery voltage. The external transistor accounts for most
of the circuit’s power dissipation; therefore, the
controller temperature remains relatively constant. The
result is a more stable internal reference, yielding a more
stable battery-voltage limit.
In some applications, intermittent loads can exceed the
main battery’s power capability. A solution to this
problem is to provide an additional, rechargeable battery
to supply the excess current during a high-load transient.
The main battery then recharges the auxiliary battery in
preparation for the next transient. Two-way pagers are a
good example of this arrangement. Pagers generally run
from a single AA alkaline battery, but the load during
transmission is too high for an AA battery to handle. An
additional NiCd battery powers the transmitter, and it
can be recharged when the transmitter is off, which is
most of the time.
R1 and R3 determine the output current. R1 senses the
charging current, and R3 sets the level at which the current
is regulated. Current out of the ISET terminal is equal to
1/1000 of the voltage between CS+ and CS-. The current
regulator controls the ISET voltage at 2V; in this case, the
current limit [2000 / (R3 + R1)] is 1A.
Control loops for the voltage and current limits have
separate compensation points (CCV and CCI), which
simplifies the task of stabilizing these limits. The ISET
and VSET terminals allow for adjustment of the current
and voltage limits.
Cradle chargers
For cell phones and many other devices, the preferred
battery-charging method involves the use of a separate
“cradle charger” into which you place the device or the
battery pack (like a baby in its cradle). Because the charger
unit is separate, its generated heat is less of a concern than
it would be if the charger were integrated into the device.
R1
0.2Ω
DCIN
3.7V TO 20V
C2
10nF
Q1
FZT749
EC10DS10
C1
4.7µF
R2
660Ω
CS+
DCIN
CS-
DRV
BATT
VSET
VL
R4
100k
The simplest circuit for use in a cradle charger is usually
a linear-regulator charger. Linear regulators drop the
difference voltage (between the dc power source and the
battery) across a pass transistor operating in its linear
region (hence the name linear regulator). However, the
dissipated power (the charging current times the drop
across this transistor) can cause overheating if the
charger is confined to a small space without airflow.
PWROK
ON
C3
0.01µF
R3
10k
MAX846A
ISET
CCI
CCV
C4
0.01µF
C5
4.7µF
For example, consider a four-cell NiCd battery charged at
1A. NiCd batteries usually terminate charging at approximately 1.6V or 1.7V per cell, but the voltage can be as
OFFV
GND
PGND
CELL2
Figure 1. Designed for single lithium-ion cells, this battery-charging
circuit is ideal for use in a stand-alone cradle charger.
4
allows you to shift the charger’s switching noise away
from sensitive frequency bands.
Built-in battery chargers
For some larger systems, including laptop computers,
the battery charger is built in as part of the system. The
charger’s efficiency in this arrangement is critical—not
to ensure maximum energy transfer, but simply to
minimize heat generation. Heat elevates temperature,
and operation at elevated temperatures shortens a
battery’s life. Because this application requires high efficiency over the entire battery-voltage range, the charger
should rely on a switching regulator, whose power dissipation is relatively low and independent of the input-tooutput voltage drop.
A linear regulator is generally larger than an equivalent
switching regulator because it dissipates more power
and requires a larger heatsink. Consequently, the extra
time necessary to design a smaller, more efficient
switching charger is usually justified. One such design is
the 4-cell NiCd/NiMH charger shown in Figure 2. It has
no provision for terminating the charge; it operates in
conjunction with a controller that monitors voltage
across the battery and shuts off the charger when conditions are met. Many systems already include a controller
suitable for this purpose. If your system does not have
one, you will need a low-cost, stand-alone microcontroller (µC) that includes an on-board analog-to-digital
converter. A number of such µCs are available.
The main drawback of switching regulators is the need
for a passive inductor/capacitor filter, which converts
the switched output voltage to a dc level suitable for
the battery. In some cases, the battery capacitance is
sufficient to replace the capacitor in this filter; however,
as mentioned earlier, a battery’s capacitance can vary
greatly with frequency. Characterize it carefully before
committing to a design.
The charger IC (MAX1640) chops the input voltage
using a switching transistor (N1A) and a synchronous
rectifier (N1B). This chopped voltage is placed across
the inductor to form a current source. When the charger
is turned off, diode D2 prevents current flow from the
charged battery back into the voltage source.
Another drawback of switching regulators is the noise
generated by their switching action. This problem can
usually be avoided with proper layout techniques and
shielding. For applications in which certain frequencies
should be avoided, many switching chargers can be
synchronized to an external signal—a capability that
In addition to “off,” the MAX1640 operates in one of
three modes as determined by the digital inputs D0 and
D1: fast charge, pulse-trickle charge, and top-off charge
(Table 1). In fast-charge mode, the charging current is
6V to 24V
47µF
35V
47µF
35V
0.33µF
IN
LDOL
47µF
16V
N1A
1/2
Si4539
LDOH
PDRV
0.1µF
D2
D0
D1
FROM
CONTROLLER
47µH
CDRH125-470
NDRV
N1B
1/2
Si4539
TOFF
MAX1640
68k
MBRS130L
CS+
0.1Ω
REF
0.01µF
600k
200k
SET
68k
TO ADC
CSR6
TERM
GND
CC
200k
R7
0.01µF
Figure 2. This four-cell NiCd or NiMH battery charger can be incorporated into a larger system.
5
4-CELL
NiCd OR
NiMH
BATTERY
circuit. R6 and R7 establish this voltage limit as VLIMIT =
VREF [(R6 + R7) / R7].
Table 1. Charging states for the MAX1640
D0
D1
MODE
OUTPUT CURRENT
0
0
Off
—
0
1
Top-off charge
VSET / (13.3RSENSE)
1
0
Pulse-trickle charge
VSET / (13.3RSENSE)
(12.5% duty cycle)
1
1
Fast charge
VREF / (13.3RSENSE)
A similar circuit charges two Li+ cells in series (Figure 3).
It differs mainly in the accuracy of its charging voltage,
which is better than the 1% required by Li+ batteries. Also
unlike the Figure 2 charger, this one employs an
n-channel MOSFET for the high-side switching transistor.
When turned on, this transistor’s source and drain
voltages are approximately equal to VIN, but the gate
voltage must be higher than VIN to allow the use of inexpensive n-channel MOSFETs. This elevated gate drive is
achieved by charging C7 and adding its voltage to VIN.
150mV divided by the current-sense resistor value (0.1Ω),
or 1.5A in this case. In top-off-charge mode, the voltage at
SET produces 24.5% of the fast-charge current, or 381mA
in this case. The current in pulse-trickle-charge mode is the
same as in top-off mode, but it is pulsed with a 12.5% duty
cycle. Frequency is determined by the resistor connected at
TOFF (68kΩ). In this case, the frequency is 3.125MHz / R3
= 46Hz. The average pulse-trickle current is therefore 0.125
x 381mA = 47.6mA.
Charging current for the circuit shown in Figure 3 is
determined by current-sense resistor R1: 185mV / R1 =
925mA for the 200mΩ value shown. This current can be
adjusted linearly to lower values by varying the voltage at
the SETI terminal. Similarly, you can adjust VOUT by
varying the voltage at the VADJ terminal. Because
varying VADJ over its full range (0V to 4.2V) changes
V OUT by only 10% (0.4V per cell), you can achieve
better than 1% output accuracy using 1% resistors. (Onepercent-accurate resistors degrade the output accuracy by
only 0.1%.)
The circuit in Figure 2 should terminate a charge when
∆V/∆t equals zero or becomes negative (according to
whether a NiMH or NiCd battery is being charged).
However, if termination fails to occur, the circuit imposes
a secondary voltage limit to prevent the battery voltage
from rising too high. As an absolute maximum, the
charging voltage for NiCd and NiMH batteries should not
exceed 2V per cell, or 8V for the 4-cell battery in this
Terminals CELL0 and CELL1 set the battery’s cell count
as shown in Table 2. (VL indicates the 5V level that
powers the chip.) The charger can handle as many as four
Li+ cells in series. Though not shown in Figure 3, the
MAX745 can also terminate charging upon reaching a
VIN
D2
1N4148
C5
4.7µF
VL
C1
0.1µF
DCIN
REF
BST
THM/SHDN
DHI
R3
100k
1%
LX
SETI
CLO
MAX745
VADJ
PGND
R11
100k
1%
C6
0.1µF
C2
R2
0.1µF 10k
CS
CCV
C7
0.1µF
M1B
1/2 IRF7303
M1A
1/2 IRF7303
L1
22µH
D1
MBRS
340T3
D6
MBRS
340T3
R1
0.2Ω
BATT
IBAT
C8
47nF
BATTERY
CELL0
CCI
GND
CELL1
Figure 3. This charger generates a 1%-accurate charging voltage suitable for charging two lithium-ion batteries in series.
6
C9
68µF
as the System Management Bus (SMBus™), which is
derived from the I2C protocol. A large base of I2C-compliant
µCs capable of controlling peripherals on the SMBus is
already available.
Table 2. Cell-count setting for the MAX745
CELL0
CELL1
NUMBER OF CELLS
GND
GND
1
VL
GND
2
GND
VL
3
VL
VL
4
Smart batteries also provide an elegant solution to the
problem of fuel gauging. In a system run by ordinary noncommunicating batteries, the host knows the state of the
battery only when it has been fully charged or discharged.
Smart batteries, on the other hand, remember their charge
state. When such batteries are switched in and out of the
host, the fuel gauge is able to maintain the same level of
accuracy as it would under continuous operation.
temperature limit monitored by a thermistor. When the
battery temperature exceeds this limit (determined by an
external resistor and thermistor connected to the THM/
SHDN terminal), the charger shuts off. Hysteresis associated with this threshold enables the system to resume
charging when a declining battery temperature causes the
THM/SHDN voltage to fall 200mV below its 2.3V
threshold.
In the smart-battery-compliant charger shown in Figure 4,
the controller IC includes an SMBus interface that allows
it to communicate with the host computer and the smart
battery under charge. Because the switching regulator and
its small, power-efficient current-sense resistor cannot
achieve a 1mA (min) resolution in charging current, the
first 31mA (five LSBs) of output current are supplied by
an internal linear current source.
Smart-battery chargers
To preserve high efficiency (89%), the system activates a
switch-mode current source when programmed for output
currents of 32mA or more. However, the linear source
remains on to ensure monotonicity in the output current
regardless of the current-sense resistor’s value or offset in
the current-sense amplifier. Transistor Q1 off-loads an
otherwise heavy power dissipation in the internal linear
regulator, which occurs when the input voltage is much
greater than the battery voltage. Q1’s base is held approximately 5V below the input voltage. Voltage across the
internal current source is less than 5V; therefore, power
dissipation in the current source remains below 160mW.
Smart batteries represent a new technology that is helping
designers and consumers alike. Smart-battery packs include
a controller that can “talk” through its serial port to tell an
external charger what kind of charging routine the battery
requires. This arrangement helps designers, because they
can design a single charger that handles all batteries
compliant with the smart-battery standard.
Smart batteries also benefit consumers, who can replace a
given battery without regard to its type, as long as the
replacement is smart-battery compliant. The smart-battery
specification allows any manufacturer to participate in the
market, and the resulting competition leads to standard
products and lower prices.
A diode (D3) is placed in series with the inductor to prevent
a flow of reverse current out of the battery. IC2’s high
switching frequency (250kHz) permits the use of a small
inductor. The circuit accepts inputs as high as 28V, and
provides pin-selectable maximum output currents of 1A,
2A, and 4A.
The smart-battery specification was defined by a consortium
of companies that manufacture batteries, computers, and
related products. It defines the way the battery pack connects
to the host system and the way it communicates with the
host. It communicates via a two-wire serial interface known
SMBus is a trademark of Intel Corp.
7
4.7V, 5%
500mW
0.1µF
IOUT
INTERRUPT
(TO HOST)
DCIN
0.1µF
33Ω
FZT749
Q1
1µF 33Ω
1µF
VIN
5.1k
0.1µF
VL
BST
C1
C2
INT
IRF7303
2x
22µF
35V
M1
SEL
DH
DACV
D3
MBRD835L
LX
IC2
0.022µF
MBRS
130LT3
D1
MBRS
130LT3
IRF7303
MAX1647
33µH
M2
CCV
DL
10k
PGND
1.0Ω
0.1Ω
CCI
CS
BATT
0.1µF
0.047µF
SDA
SCL
GND
REF
THM
1500pF
100Ω
100Ω
22µF
35V
0.1µF
10k
1%
10k
1%
2 x 1N4735
OUT
VIN
MAX874
GND
T
D
C
+
SMART-BATTERY CONNECTOR
Figure 4. This charger is compliant with the smart-battery specification, and communicates with the host computer and a smart battery via the
SMBus interface.
8
DESIGN SHOWCASE
Load switcher draws only 6µA
Inducing a signal of either polarity in the coil (by
passing a magnet near it, for example) causes the dual
op amp to draw more current from its VCC terminal.
The increase produces a voltage across R1 that
exceeds Q1’s VBE threshold, activating the complementary monostable multivibrator consisting of Q1,
Q2, and associated components. As a result, Q1
connects battery voltage to the load. For many applications, you can replace the monostable with a simple
pnp output stage.
Figure 1’s circuit draws only 6µA, but it enables a
small signal of ±1mV or more to switch relatively
large load currents. It takes advantage of the IC’s very
low quiescent current—1.2µA (max) per amplifier
(less than a typical battery’s self-discharge)—which is
able to flow through R1 without turning on Q1. When
operated with a sensing coil (as shown) and stimulated
by a magnet, the circuit performs the function of a reed
switch, but with greater sensitivity. Other applications
include alarm systems, bipolar threshold sensing, and
audio volume switching.
A similar idea appeared in the 7/4/96 issue of EDN.
VIN
6V to 9V
R1
100k
2µF
Q1
BC213
10k
0.1µF
1
1M
7
8
1M
3.3k
V CC
2
6
100k
3
100k
5
MAX417
10µF
GND
4
1M
Q2
BC548
0.1µF
51Ω
47µF
0.1µF
100k
51Ω
51Ω
0.1µF
SENSING COIL
60T
51Ω
0.1µF
Figure 1. This load switcher enables a small signal to turn on a much larger load current.
9
R LOAD
DESIGN SHOWCASE
Single-cell boost converter generates
auxiliary bias for LCD
The circuit of Figure 1 generates two supply voltages
commonly required in pagers and other portable
instruments that have small, graphic liquid-crystal
displays: a regulated 3.3V at 100mA, and a regulated
negative output suitable for use as an LCD bias
voltage. Overall efficiency is about 80%.
winding. At minimum battery voltage (0.8V), the T1
primary sees 3.3V - 0.8V = 2.5V; thus, the 6:1 turns
ratio produces 6(2.5) = 15V in the secondary. At
maximum battery voltage (1.65V), the primary sees
only 1.65V, producing 9.9V in the secondary. MOSFET
Q1 stabilizes this output by interrupting the secondary
current, introducing the regulation necessary to generate
a constant (and therefore useful) negative output.
The main 3.3V supply is provided by a boost converter
(IC1) operating in its standard configuration. The
auxiliary bias voltage is provided by an extra flyback
winding (the T1 secondary) and is regulated via Q1 and
the low-battery detector internal to IC1.
The regulator employs IC1’s low-battery detector (a
comparator/reference combination) as an on/off
controller for Q1. Normally, the input (LBI) monitors
a positive battery voltage and drives the output (LBO)
low when LBI drops below 1.25V. In this circuit, the
As the battery discharges, its declining terminal voltage
causes a decline in the voltage induced in the flyback
T1
PRIMARY INDUCTANCE = 22µH
N P /N S TURNS RATIO ≥ 6:1
V IN
(SINGLE CELL)
0.8V TO 1.65V
1N5817
VO
-8V
5mA
68µF
10V
68µF
5V
P
S
Q1
VN10K
1N5817
3.3V
100mA
8
47k
LX
OUT
IC1
MAX856
3/5
SHDN
LBO
3
0.1µF
LBI
REF
6
2
R1
2.2M
1
4
5
GND
R2
470k
7
R1
(1.25V - V CTRL ) + 1.25V
VO =
R2
(-8V FOR THE VALUES SHOWN)
V CTRL
LCD ON
Figure 1. This circuit establishes a regulated VCC (3.3V or 5V) and a regulated, negative, LCD-bias voltage (-8V in this case).
10
A logic signal at the LCD ON terminal provides a
means to enable and disable the negative output. This
signal voltage also sets the feedback level, and
therefore should have a full CMOS swing. In addition,
you can apply a variable voltage at LCD ON to make
the output variable. Voltages below 1.25V turn the
output off, and voltages greater than 1.25V change the
output with a slope of -R1/R2(VIN - 1.25V), with an
offset of 1.25V. This variable input, generated by a lowpower digital-to-analog converter or the filtered pulsewidth-modulator output from a microcontroller, can
vary the LCD contrast in response to a change in
temperature or viewing conditions. (See the output
voltage equation in Figure 1.)
R1/R2 divider holds LBI between VCTRL (normally
3.3V) and the LCD bias output (normally -8V). The
R1 and R2 values are chosen such that LBO turns Q1
off when the LCD bias becomes too negative (and
pulls the LBI voltage below 1.25V). Load current then
causes the LCD bias to drift upward (toward 0V) until
LBI exceeds 1.25V, which causes Q1 to turn on again.
The bias output makes excursions above and below its
nominal value, producing a ripple voltage whose
frequency depends on the size of the output filter
capacitor, the output load, and the hysteresis in IC1’s
low-battery comparator. This frequency is about 150Hz
for the circuit shown, and the hysteresis (about 25mV)
dominates ripple magnitude. Multiplied by the R1/R2
ratio, the hysteresis results in a ripple amplitude (for
-8V/1mA output) of about 100mV. Because ripple is
essential to operation in this hysteretic converter, it
cannot be reduced directly. Most LCDs are very
forgiving of bias ripple. Otherwise, ripple can be
minimized by adding an RC network or linear regulator
at the negative output.
The main voltage can be changed from 3.3V to 5V by
grounding the 3/5 terminal on IC1. In that case, the
turns ratio should also be reduced to 3:1 because the
highest battery voltage will induce 3.35V in the T1
primary. Then adjust the R1 and R2 values to obtain
the desired negative-output level.
A similar idea appeared in the 11/4/96 issue of
Electronic Design.
11
DESIGN SHOWCASE
Supply generates 5V from
solar-cell power
Applications powered by solar cells often require a
+5V power supply, but the cells typically provide
only a 0.8V to 1.4V terminal voltage, with a 3A to 4A
current capacity. Most dc-dc converters cannot start at
such low voltages, nor can they start under full load.
A two-step approach (Figure 1) enables the system to
start up and produce the 5V rail under full load.
(ESR) capacitor. This input capacitor also minimizes
supply-voltage fluctuations by lowering the solar
cell’s output impedance. The 330µH inductor (L1)
enables a low start-up voltage for IC1. IC1’s 15µF, lowESR output capacitor (C2) minimizes supply-voltage
ripple for IC2.
Make sure that the output-stage inductor (L2) is
properly rated for maximum peak inductor current and
maximum saturation current. The current-sense
resistor (R1) limits peak current in this inductor to
100mV/R3. IC2’s 470µF, low-ESR output capacitor
(C3) reduces output ripple to less than 80mVp-p for
load currents as high as 600mA. Smaller output loadcurrent values permit smaller values for C1 and C3.
IC1 operates in bootstrapped mode (powered by its own
output) and boosts the input voltage from 0.8V (min) to
5V. Powered by 5V, the second converter (IC2) then
delivers as much as 0.5A. IC2’s output voltage (5V) is
programmed by R2 and R3. IC1 thus enables IC2 to
start regardless of load conditions. Providing IC2 with a
full +5V supply also minimizes RDS(ON) in the external
n-channel MOSFET by providing a 0V to 5V (max)
gate drive (voltage swing).
Figure 2 shows the overall conversion efficiency for
different input voltages versus load current. The
circuit delivers 200mA or more for VIN = 0.8V, and
450mA or more for VIN = 1.5V.
To suppress input ripple due to power-supply switching,
specify C1 as a 220µF, low equivalent series resistance
3
REF
LX
OUT
0.1µF
SHDN
IC1
L2
22µF
D03340-223
(COILCRAFT)
L1
330µF
D03316-334
(COILCRAFT)
C1
220µF
(AVX)
MAX866
8
D1
MBR50530
(MOTOROLA)
2
V+
EXT
1
Q1
MTD20
N03HDL
8
C3
470µF
(AVX)
6
CS
1
IC2
C2
15µF
(AVX)
0.1µF
R1
0.02Ω
LR2010-01-R020
(IRC)
MAX1771
4
LBI
5
D2
NSQ03A02
(NIEC)
90
V OUT
5V at 0.5A
VIN = 1.5V
VIN = 1.1V
5
GND
7
EFFICIENCY vs. LOAD CURRENT
100
REF
SHDN
AGND
6
FB
EFFICIENCY (%)
V IN
0.8V TO 4.5V
R2
91k
80
VIN = 1V
VIN = 0.8V
70
60
VIN = 0.9V
50
VIN = 1.2V
3
GND
7
R3
39k
40
1
100
LOAD CURRENT (mA)
Figure 1. This two-stage step-up converter derives 0.5A at 5V from a typical
solar-cell array, and guarantees start-up under full load.
12
Figure 2. Efficiency for the Figure 1 circuit
varies with input voltage and
load current.
1000
DESIGN SHOWCASE
Battery-switchover circuit
accommodates 3V systems
Portable systems often offer the flexibility to operate
either from an internal battery or from an ac-to-dc
wall adapter. Many such systems include circuitry that
switches automatically between the internal battery
and an external source as the user connects and
disconnects the wall adapter. The circuit shown in
Figure 1 implements this idea with a dual linear
regulator, one side of which is preset for a 2.84V
regulated output. (Other versions of the IC offer 2.8V
and 3.15V outputs.)
input bypass capacitor (C1) provides enough holdup
time for seamless transitions between the battery and
adapter voltages.
Resistors R1 and R2 sense the wall-adapter voltage
and determine the switchover threshold (VSW):
 R1 + R2 
 130k + 100k 
VSW = VSET 
 = 1.25V 
 = 2.875V
R2 
100k



Diode D1 isolates the wall-adapter voltage so the
battery cannot cause limit cycling by retriggering the
switchover. D2 holds the IC’s Dual Mode™ input in
external-feedback mode by maintaining a minimum
voltage at the SET2 input.
The other side of the dual regulator is configured to
allow user-adjustable outputs, and in this case
monitors the wall-adapter voltage. When you remove
that voltage by unplugging the adapter, the regulator’s
pass transistor routes battery current into the IC to
support the 2.84V output. (Current flow in this transistor is counter to that of most applications.) The
Battery operation interposes two pass transistors in
series between the battery and the regulated output,
doubling the regulator’s dropout voltage. These transistors each have about 1.1Ω on-resistance. To
prevent battery current from bleeding
through the OUT2 transistor’s
intrinsic body diode when operating
from the wall adapter, the wall-adapter
voltage should be equal to or greater
C1
than the maximum battery voltage.
D2
(1N4148)
D1
(1N4001)
5VDC
FROM WALL
ADAPTER
7
SHDN1
6
SHDN2
2
2µF
IN
P
OUT1
2.84V
100mA
1
1.25V
C2
1µF
MAX8865S
R1
130k
P
5
SET2
OUT2
R2
100k
If you turn the regulators on and off
with the shutdown inputs SHDN1 and
SHDN2, choose the MAX8865 rather
than the MAX8866, whose autodischarge feature will attempt to
discharge the battery. As shown, the
MAX8865S with a 5V wall adapter and
3-cell battery provides up to 100mA
at 2.84V.
SET1
GND
8
3
4
3-CELL
BATTERY
4.5V
A similar idea appeared in the 2/3/97
issue of Electronic Design.
Dual Mode is a trademark of Maxim Integrated
Products.
Figure 1. This linear voltage regulator with automatic-switchover circuitry maintains a 2.84V
regulated output as you connect and disconnect the wall-adapter voltage.
13
DESIGN SHOWCASE
Off-the-shelf transformer
adapts controller for SLIC applications
A new multiwinding transformer (configurable by the
user for a variety of applications) enables an inverting
controller to produce the high negative voltages
required by an ISDN board or other telephone-line
card (Figure 1).
regulated -24V or -48V; for generating ring tones, it
requires a loosely regulated -70V. The five-ringerequivalent requirement demands 9W to 10W from the
-70V output, which translates to a full-load IOUT of
about 150mA.
Such line cards employ a subscriber-line interface
circuit (SLIC) such as the 79R79 ringing SLIC from
AMD. This IC generates the off-hook and on-hook
signal transmission, ring-tone generation, and ring-tip
detection that constitute an analog telephone interface.
For off-hook signal transmission, it requires a tightly
IC1 is an inverting switching regulator that normally
converts a 3V to 16V input to a fixed output of -5V or
an adjustable output. In the circuit shown, three pairs
of windings in series (provided by a single, off-theshelf, multiwinding transformer) enable IC1 to
generate the high voltages needed by a SLIC IC.
C5, C6
68µF
20V
C4
0.33µF
V+
R3
68mΩ
SHDN
U1
REF
CS
MAX774
R2
100k
EXT
P1
FB
C3
0.1µF
C2
1.0nF
C1
100pF
100V
OUT
GND
-70V
OUTPUT
R1
1.6M
C10
10µF to
220µF
63V
C8
0.1µF
100V
-24V
OUTPUT
C9
220µF
25V
D2
200V
L1
10µH, 3A
D1
≥60V
C7
0.1µF
50V
Figure 1. Dual power-supply outputs for a ringing SLIC IC (not shown) can be derived from a single inverting controller (IC1)
by connecting several windings in an autotransformer configuration.
14
Connecting a diode and output capacitor (D1 and
C7/C9) at the first or second pair of windings produces
-24V (as shown) or -48V, respectively. Feedback to
the IC via R1 and R2 achieves tight regulation at this
output. The transformer turns ratios establish a loose
regulation at the -70V output.
capacitor (C8/C10) to the -24V output instead of to
ground. This connection also simplifies board layout
and enhances stability.
The circuit shown in Figure 1 is optimized for compact
surface-mount applications, and produces a worst-case
ripple voltage at the -24V output of approximately
200mVp-p. To reduce this ripple, increase the
capacitor values and use through-hole filter capacitors
with low equivalent series resistance, such as the
Sanyo MV-GX series. To prevent interference, place
the dc-dc converter on a corner of the board opposite
the sensitive audio circuitry. Cross-regulation graphs
(as a guide to the preloading performance) and a tested
pc board layout are available on request from Maxim’s
applications department.
The circuit shown can service a five-telephone load
(10W) from an input of 12V ±10%. It operates down
to 3V, and produces about 2.4W at 3.3V and 3.9W at
5V. The -70V output depends on cross regulation
with respect to the -24V output, and is therefore
affected by relative loading on the two outputs (i.e.,
whether one is heavily loaded and the other lightly
loaded, or vice-versa).
Multifilar transformer windings improve cross regulation by increasing the voltage coupling between
outputs and by reducing the voltage spiking caused
by leakage inductance. Cross regulation is also
improved by connecting the -70V output’s filter
A similar idea appeared in the 11/4/96 issue of
Electronic Design.
15
NEW PRODUCTS
each DAC, a 1µA power-down mode, and
an asynchronous load-DAC input pin. Its
3-wire serial interface is compatible with
SPI™/QSPI™ and Microwire™ standards.
Low-power 8-bit
DACs offer voltage
output in a tiny
package
As upgrades to the existing dual
MAX549B and single MAX550B, the software-compatible MAX549A/MAX550A
have double-buffered inputs and an enhanced set of programming commands. The
MAX550A also has an asynchronous loadDAC input pin.
The MAX548A/MAX549A†/MAX550A†
digital-to-analog converters (DACs) are
8-bit, voltage-output serial devices available
in single and dual versions. They offer low
voltage, low power, and the tiny, proprietary
8-pin µMAX package (50% smaller than an
8-pin SO).
The MAX548A/MAX549A/MAX550A
are available in 8-pin DIP and µMAX
packages specified for the commercial (0°C
to +70°C) or extended-industrial (-40°C to
+85°C) temperature range. Prices start at
$1.65 (1000 up, FOB USA).
The dual MAX548A operates from a
single +2.5V to +5.5V supply. Its low
operating current, including current for the
internal voltage reference (VREF is internally connected to VDD), is 150µA at VDD
= 2.5V and 300µA at V DD = 5V. The
MAX548A features a double-buffered
input, independent software control of
†Previously announced.
SPI and QSPI and trademarks of Motorola, Inc.
Microwire is a trademark of National
Semiconductor Corp.
unipolar/bipolar and single-ended/differential operation. Other features include a hardwired SHDN input, an internal/external
clock and reference, and a serial strobe that
provides the end-of-conversion signal.
Low-cost, 3V,
multichannel
8-bit ADCs are the
smallest available
The MAX1111 comes in 16-pin DIP
and QSOP packages, and the MAX1110
comes in 20-pin DIP and SSOP packages.
Both are available in versions specified
for the commercial (0°C to +70°C),
extended-industrial (-40°C to +85°C), or
military (-55°C to +125°C) temperature
range. Prices start at $2.45 for the
MAX1111 and $2.70 for the MAX1110
(1000 up, FOB USA).
The MAX1110/MAX1111 analog-todigital converters (ADCs) are complete,
low-power, 3V, 8-bit devices that include
an analog-input multiplexer, internal 2V
reference, serial interface, and internal
clock. The 4-channel MAX1111 comes in
a 16-pin QSOP (same size as an 8-pin
SO), and the 8-channel MAX1110 comes
in a small 20-pin SSOP.
Operating from a single +2.7V to
+5.5V supply, these low-power ADCs
sample to 50ksps, yet draw
BEST INTEGRATION
only 120µA from the supply.
REFERENCE
For battery-operated applications, a 2µA power-down
T/H
M
8-BIT ADC
mode reduces power consumpU
X
tion at lower sampling rates.
CLK
POWERDOWN
BEST POWER
60µA @ 10ksps
4µA @ 1ksps
BEST POWER SUPPLIES
+2.7V to +5.5V
operation
BEST SPEED : POWER
50ksps : 150µA
BEST SIZE
QSOP-16
(same size as SO-8)
16
1111
The MAX1110/MAX1111
can be programmed to power
down at the end of each
conversion and power up when
the 2MHz serial interface is
accessed. The serial interface is
SPI/QSPI and Microwire
compatible. The analog inputs
are software configurable for
SPI™/MICROWIRE™
COMPATIBLE
SERIAL INTERFACE
5V, 12-bit/10-bit
ADCs connect
directly to 3V µPs
The 12-bit MAX1202/MAX1203 and
10-bit MAX1204 data-acquisition systems
are designed for use in mixed-supply
applications (5V analog; 3V or 5V digital).
They combine a successive-approximation
ADC converter with an 8-channel multiplexer, high-bandwidth track/hold, 4.096V
reference (MAX1202/ MAX1204 only), and
a serial-data interface.
Rather than adding external level
translators, the user can set output logic
levels to 3V, 3.3V, or 5V by simply
applying the desired logic level to the VL
input pin. In addition, the logic-high input
levels are guaranteed down to 2V for
compatibility with most 3V systems. The
devices provide sampling rates to 133ksps
and draw only 1.5mA from a single +5V
or dual ±5V supply.
The MAX1202/MAX1203/MAX1204
have a 2MHz, 4-wire serial interface that
connects directly to SPI and Microwire
devices. They feature an internal clock and a
serial-strobe output that allows direct
connections to the TMS320 family of
digital-signal processors. A SHDN input
and two software-selectable modes are also
included for powering down the devices.
The MAX1202/MAX1203/MAX1204
are available in 20-pin DIPs and 20-pin
SSOPs, in versions specified for the
commercial (0°C to +70°C), extendedindustrial (-40°C to +85°C), or military
(-55°C to +125°C) temperature range.
Prices start at $7.09 (1000 up, FOB USA).
NEW PRODUCTS
The MAX5354/MAX5355 serial
interface is SPI™/QSPI™ and Microwire™
compatible, and the input is double
buffered. All logic inputs are TTL/CMOS
compatible, and all are buffered with
Schmitt triggers that allow a direct
interface to opto-couplers.
MAX5354/MAX5355 are available in
8-pin DIP and µMAX packages, in versions
specified for the commercial (0°C to
+70°C), extended-industrial (-40°C to
+85°C), or military (-55°C to +125°C)
temperature range. Prices start at $2.90
(1000 up, FOB USA).
SPI and QSPI are trademarks of Motorola, Inc.
Microwire is a trademark of National
Semiconductor Corp.
Small, low-power,
12-bit VOUT DACs
have configurable
outputs
The MAX5352/MAX5353 12-bit
DACs include precision output amplifiers, and are available in small 8-pin
DIP or µMAX packages. The MAX5352/
MAX5353 operate from single supplies
of +5V and +3.3V, respectively. Both
draw 240µA in normal operation and
only 10µA in shutdown mode.
Rail-to-Rail is a registered trademark of Nippon
Motorola Ltd.
These op amps are unity-gain stable for
any capacitive load. Their outputs swing
rail-to-rail, and their input common-mode
and a spurious-free dynamic range (SFDR)
of -83dBc at 5MHz with RL = 100Ω. The
MAX4309 delivers a -3dB bandwidth of
200MHz and an SFDR of -83dB at 5MHz
with RL = 100Ω. Other features include
wide output-voltage swings, high outputcurrent capability (90mA), ultra-low
differential gain/phase (0.004%/0.008°),
and fast settling times (8ns to within
0.1%, and 12ns to within 0.01%,
respectively).
400MHz voltagefeedback op amps
have ultra-low
-93dB distortion
The MAX4308/MAX4309 voltagefeedback op amps’ high speed and ultra-low
distortion make them ideal for use in lowlevel, 12-bit to 16-bit applications in
medical imaging, instrumentation,
and RF-signal processing.
MAX4308/MAX4309
08
Unlike other 10-bit DACs, these
devices provide access to the amplifier’s
inverting input, allowing configuration for
specific gains or high output current capability. The DAC output swings rail-to-rail
and settles in 16µs. At power-up, the
power-on-reset circuitry clears the DAC
output to 0V.
High bandwidth, low power consumption, and small packages make these op
amps ideal for use in portable equipment
and other low-power, single-supply applications. The MAX4162 comes in a tiny 5-pin
SOT23 or 8-pin SO, and the MAX4163
comes in an 8-pin µMAX or SO. Both are
specified for the extended-industrial
temperature range (-40°C to +85°C). Prices
start at $0.85 (1000 up, FOB USA).
The MAX4162/MAX4163/MAX4164
micropower op amps have Rail-to-Rail®
input/output (I/O) and an exceptionally high
bandwidth for their power consumption.
Gain-bandwidth product is 200kHz, and
typical quiescent current is only 25µA
(40µA max). The single MAX4162 comes
in a 5-pin SOT23 package. These devices
operate from either a single +2.7V to +10V
supply or dual ±1.35V to ±5V supplies.
43
The MAX5354/MAX5355 10-bit
digital-to-analog converters (DACs) are
available in small 8-pin µMAX packages
(50% smaller than an 8-pin SO). Each
includes a precision output amplifier. The
MAX5354 operates from a single +5V
supply, and the MAX5355 operates from
a single +3.3V supply. Both draw 240µA
in normal operation and only 2µA in
shutdown mode.
range extends 250mV beyond the supply
rails. A proprietary internal architecture
ensures very high common-mode input
rejection without the mid-swing nonlinearities found in other rail-to-rail op amps.
SOT23 rail-to-rail I/O
op amps provide
200kHz GBW at
25µA ISUPPLY
HARMONIC DISTORTION vs.FREQUENCY
Decompensated versions of
the MAX4108/MAX4109, the
MAX4308 requires a +5V/V
(min) closed-loop gain, and the
MAX4309 requires a +10V/V
(min) gain. The MAX4308
delivers a 220MHz -3dB
bandwidth, 1200V/µs slew rate,
-20
VOUT = 2Vp-p
MAX4308: AVCL = +5
MAX4309: AVCL = +10
-30
HARMONIC DISTORTION (dBc)
10-bit serial VOUT
DACs available in
8-pin µMAX
-40
MAX4308
-50
–
-60
-5V
-70
2ND HARMONIC
-80
-90
3RD
HARMONIC
-100
0.1
Access to the amplifiers’ inverting
input allows the user to configure either
device for specific gains and high output
current capability. The DAC output
swings rail-to-rail and settles in 14µs. At
power-up, the power-on-reset circuitry
clears the DAC output to zero.
The MAX5352/MAX5353 serial
interface is SPI/QSPI and Microwire
compatible, and the input is double
buffered. All logic inputs are TTL/CMOS
compatible, and all are buffered with
Schmitt triggers, allowing a direct interface
to opto-couplers.
17
+5V
+
The MAX4308/MAX4309
are available in 8-pin SO
packages specified for the
extended-industrial temperature range (-40°C to +85°C).
Prices start at $3.88 (1000 up,
FOB USA).
1
10
100
FREQUENCY (MHz)
The MAX5352/MAX5353 are available in 8-pin µMAX packages (50% less
area than an 8-pin SO) and 8-pin DIPs, in
versions specified for the commercial (0°C
to +70°C), extended-industrial (-40°C to
+85°C), or military (-55°C to +125°C)
temperature range. Prices start at $4.95
(1000 up, FOB USA).
NEW PRODUCTS
Ultra-low-power
amplifiers offer
SOT23 packaging
and Hi-Z shutdown
The MAX4180–MAX4187 currentmode amplifiers combine high speed, low
distortion, and excellent video specifications with ultra-low power consumption.
They operate from a single +5V supply or
from dual ±2.25V to ±5.5V supplies, and
require only 1mA of supply current per
amplifier while delivering output currents
up to ±60mA.
Optimized for applications with
+2 (6dB) or greater closed-loop gains, the
MAX4180/MAX4182*/MAX4183*/
MAX4186* provide a 240MHz -3dB
bandwidth and a 90MHz 0.1dB bandwidth.
The MAX4181/MAX4184*/MAX4185*/
MAX4187*, optimized for +1V/V (0dB) or
greater gains, provide a 270MHz -3dB
bandwidth and a 60MHz 0.1dB bandwidth.
3MHz, low-power
op amps with
rail-to-rail I/O
available in SOT23
The MAX4330–MAX4334 are a new
family of wideband, low-power, singlesupply, Rail-to-Rail® input/output (I/O)
op amps. Available in single (MAX4330/
MAX4331), dual (MAX4332/MAX4333),
and quad (MAX4334) versions, these
devices operate from a single +2.3V to
+6.5V supply or dual ±1.15V to ±3.25V
supplies. Each op amp achieves 3MHz
gain-bandwidth from a supply current of
only 245µA per amplifier (330µA max).
The MAX4330–MAX4334’s outputs
swing within 100mV of the rails (with a
2kΩ load), and their common-mode input
voltage range extends 250mV beyond
each rail. This rail-to-rail I/O makes them
ideal for use in battery-powered
equipment and other low-power, lowvoltage, single-supply applications. In
addition, their low offset voltage (250µV
The MAX4180–MAX4187 amplifiers
are ideal for high-performance video
applications. They feature differential
gain/phase errors of 0.08%/0.03°, -73dBc
SFDR (fC = 5MHz), a fast settling time to
0.1% of 20ns, and a 400V/µs slew rate.
The MAX4180/MAX4181/MAX4183/
MAX4185 have an additional feature: a
low-power shutdown mode that lowers the
supply current to 120µA (max) and places
the outputs in a high-impedance state
(useful in multiplexing applications).
The following package options are
available: a space-saving 6-pin SOT23 or
8-pin SO for the single MAX4180/
MAX4181, an 8-pin SO for the dual
MAX4182/MAX4184, a 14-pin SO or
10-pin µMAX for the dual MAX4183/
MAX4185, and a 14-pin SO or 16-pin
QSOP for the quad MAX4186/MAX4187.
All are specified for the extended-industrial
temperature range (-40°C to +85°C). Prices
start at $1.80 (1000 up, FOB USA).
*Future product—contact factory for availability.
typical) and high speed (3MHz gainbandwidth product) are ideal for signalconditioning stages in precision, lowvoltage data-acquisition systems. For
space-critical applications, the MAX4330
comes in a tiny 5-pin SOT23 package.
Each output is capable of driving a
2kΩ load, and all amplifiers are unity-gain
stable for capacitive loads to 150pF. The
MAX4331/MAX4333 have a low-power
shutdown mode that places the outputs in
a high-impedance state and lowers the
supply current to only 9µA per amplifier.
The MAX4330 comes in a 5-pin
SOT23 package; the MAX4331 comes in
an 8-pin µMAX and SO; the MAX4332
comes in an 8-pin SO; the MAX4333
comes in a 10-pin µMAX or 14-pin SO;
and the MAX4334 comes in a 14-pin SO.
All are specified for the extendedindustrial temperature range (-40°C to
+85°C). Prices start at $0.85 (1000 up,
FOB USA).
Rail-to-Rail is a registered trademark of Nippon
Motorola Ltd.
18
Micropower,
rail-to-rail I/O
comparators come
in 5-pin SOT23
The MAX985 family of single/dual/
quad micropower comparators are
specified for single-supply operation in
the +2.5V to +5.5V range, making them
ideal for use in both 5V and 3V systems.
They also operate from dual supplies in
the ±1.25V to ±2.75V range.
MAX985 devices typically exhibit
300ns propagation delays with 100mV
overdrive while drawing 13µA quiescent
supply currents. Each output stage’s unique
design limits supply-current surges while
switching, virtually eliminating the supply
glitches typical of other comparators. This
design also minimizes overall power
consumption under dynamic conditions.
Common-mode input voltage for the
MAX985 family extends 250mV beyond
each supply rail (VEE - 0.25V to VCC +
0.25V), and large output drivers enable railto-rail output swings with loads as high as
8mA. Typical input specifications include
0.5mV offset voltage and 1pA input bias
current. Internal hysteresis ensures clean
output switching, even with slow-moving
input signals. The MAX985/MAX989*/
MAX993* have push/pull outputs that sink
as well as source current. The MAX986/
MAX990*/MAX994* have open-drain
outputs that can pull up to VCC or to any
level not exceeding VEE + 6V.
Package options include a 5-pin SO or
SOT23 for the single MAX985/MAX986,
an 8-pin SO or µMAX for the dual
MAX989/MAX990, and a 14-pin SO for
the quad MAX993/MAX994. All are
specified for the extended-industrial
temperature range (-40°C to +85°C).
Prices start at $0.66 (1000 up, FOB USA).
*Future product—contact factory for availability.
NEW PRODUCTS
1GHz current-mode
amplifiers offer
SOT23 packaging
and Hi-Z shutdown
The MAX4223–MAX4228 family of
current-feedback amplifiers combine
ultra-high speed, low distortion, and
excellent video specifications with low
power consumption. Operating from dual,
±3.0V to ±5.5V power supplies, they
produce output currents as high as 80mA
and draw only 6mA of supply current per
amplifier.
The MAX4223/MAX4224/MAX4226*/
MAX4228* have a shutdown mode
(useful in multiplexing applications) that
lowers the supply current to 350µA and
places the outputs in a high-impedance
state. The MAX4223/MAX4225*/
MAX4226 are optimized for +1V/V (0dB)
closed-loop gains, and have 1GHz -3dB
bandwidths. The MAX4224/MAX4227*/
Ultra-low-voltage
micropower
comparators
include 1.235V
±1.5% references
The MAX965–MAX970 family of
micropower comparators includes single,
dual, and quad versions; all have Rail-toRail® input/output (I/O). Their operating
voltage range is fully specified down to
1.6V, making them ideal for 2-cell batterypowered applications. Typical quiescent
supply currents are less than 3µA per
comparator.
For ultra-low-voltage operation, the
input common-mode voltage range for
each device extends to each supply rail.
The open-drain outputs simplify voltage
translation in multirail systems, and they
also provide rail-to-rail output swings
MAX4228 are optimized for +2V/V (6dB)
closed-loop gains, and have 600MHz
-3dB bandwidths (a 1.2GHz gainbandwidth product).
Precision, singlesupply op amps
have rail-to-rail I/O
Low differential gain/phase errors
(0.01%/0.02°), 0.1% gain flatness to
300MHz, and slew rates up to 1700V/µs
make these amplifiers ideal for use in
professional video applications. Their low
total harmonic distortion (-60dBc) and
fast settling time (8ns to 0.1%) make them
ideal for data communications or for
driving the inputs of high-speed analogto-digital converters.
The MAX4165–MAX4169 family of
precision, high-output-drive op amps
includes single, dual, and quad versions.
Each op amp combines low power
consumption, high output current capability (80mA minimum), and rail-to-rail
operation with exceptional DC accuracy.
These qualities provide excellent performance in portable audio and other lowvoltage, battery-powered applications.
Package options are as follows: a tiny
6-pin SOT23 or 8-pin SO for the single
MAX4223/MAX4224, an 8-pin SO for
the dual MAX4225/MAX4227, and a
10-pin µMAX or 14-pin SO for the dual
MAX4226/MAX4228. All these devices
are specified for the extended-industrial
temperature range (-40°C to +85°C).
Prices start at $2.15 (1000 up, FOB USA).
All amplifiers guarantee single-supply
operation from +2.7V to +6.5V, as well as
dual-supply operation in the ±1.35V to
±3.25V range. Quiescent supply currents
are only 1.2mA (1.4mA max) per
amplifier. The MAX4166/MAX4168 have
a shutdown mode that lowers their supply
current to 38µA (per amplifier) and places
each output in a high-impedance state.
*Future product—contact factory for availability.
when operating with an external pull-up
resistor. All inputs and outputs can
withstand a continuous short circuit to
either supply rail.
The single MAX965, dual MAX967/
MAX968, and quad MAX969 include a
1.235V ±1.5% bandgap voltage reference
for use in threshold-detector and windowcomparator applications. This reference
makes it possible to include adjustable
hysteresis.
The MAX965–MAX968 comparators
are available in 8-pin SO and µMAX
packages. The MAX969 is available in a
16-pin SO or QSOP, and the MAX970 is
available in a 14-pin SO or 16-pin QSOP.
All devices are specified for the extendedindustrial temperature range (-40°C to
+85°C). Prices start at $1.05 (1000 up,
FOB USA).
Rail-to-Rail is a registered trademark of Nippon
Motorola Ltd.
19
Each amplifier is unity-gain stable,
with a 5MHz gain-bandwidth product and
a 2V/µs slew rate. Input offset voltages are
only 250µV. PSRR is 88dB, and voltage
gain with a 100kΩ load is 120dB.
Package options include a 5-pin
SOT23 for the single MAX4165; an 8-pin
µMAX, SO, or plastic DIP for the single
MAX4166; an 8-pin SO or plastic DIP for
the dual MAX4167; a 10-pin µMAX or a
14-pin SO or plastic DIP for the dual
MAX4168; and a 14-pin SO or plastic
DIP for the quad MAX4169. All are
specified for the extended-industrial
temperature range (-40°C to +85°C).
Prices start at $0.95 (1000 up, FOB USA).
NEW PRODUCTS
Quad, wideband
current-mode
amplifiers have
0.1dB gain flatness
to 90MHz
The MAX4119/MAX4120 are quad,
low-power amplifiers with current-mode
feedback. They combine high speed with
low-power operation, operate from ±5V
supplies, and draw only 5mA of supply
current per channel. The MAX4119,
optimized for +2V/V or greater closedloop gains, delivers a 350MHz -3dB
bandwidth and 0.1dB gain flatness to
90MHz. The MAX4120, optimized for
+8V/V or greater closed-loop gains, has a
300MHz -3dB bandwidth and 0.1dB
flatness to 115MHz.
16-channel/
dual 8-channel
CMOS muxes
feature ultra-low
leakage
The MAX336/MAX337 are CMOS
analog multiplexers (muxes). The
MAX336 has four digital inputs that select
one of 16 single-ended channels, and the
MAX337 has three digital inputs that
select one of 8 differential channels. Both
devices are capable of demultiplexing as
well as multiplexing, because the onresistances (400Ω max, matched to within
10Ω) conduct equally well in both directions. Transition times are less than 500ns.
These amplifiers exhibit high slew rates
(1200V/µs at +2V/V and 1800V/µs at
+8V/V) and exceptional full-power bandwidths, making them excellent choices for
use in high-performance pulse and RGBvideo applications. They offer wide output
swings (±3.5V into a 100Ω load) and a high
80mA current-drive capability.
Other devices in this family include the
single MAX4112/MAX4113 and the dual
MAX4117/MAX4118. The MAX4119/
MAX4120 are available in a 14-pin SO and
a 16-pin QSOP; the MAX4112/MAX4113/
MAX4117/MAX4118 are available in an
8-pin SO; and the MAX4112 also comes in
an 8-pin µMAX. All are specified for the
extended-industrial temperature range
(-40°C to +85°C). Prices for the MAX4119/
MAX4120 start at $1.95 (1000 up,
FOB USA).
±20V supplies. The digital enable and
channel-address inputs remain TTL/
CMOS-logic compatible (0.8V and 2.4V
switching thresholds) over the full
operating temperature range and over the
±4.5V to ±18V power-supply range.
These parts are fabricated with Maxim’s
44V silicon-gate process.
The MAX336/MAX337 are available
in 28-pin DIP, wide-SO, SSOP, and
PLCC packages, in versions specified for
the commercial (0°C to +70°C), extendedindustrial (-40°C to +85°C), or military
(-55°C to +125°C) temperature range.
Prices start at $3.69 (1000 up, FOB USA).
MAX336/MAX337
OFF LEAKAGE vs. TEMPERATURE
1000
The MAX336/MAX337 handle Railto-Rail ® signals while operating from
single +4.5V to +30V or dual ±4.5V to
100
OFF LEAKAGE (nA)
Leakage currents are extremely low:
off leakages are less than 20pA at +25°C,
and on-channel leakages are less than
50pA at +25°C. The MAX336/MAX337
have a new design that guarantees low
charge injection (1.5pC typical), and
protection (per Method 3015.7 of
MIL-STD-883) against electrostatic
discharge (ESD) to 2000V. The MAX336/
MAX337 are improved, pin-compatible
upgrades for the industry-standard
DG506A/DG507A muxes.
V+ = +15V
V- = -15V
10
1
ICOM (OFF)
0.1
0.01
0.001
INO (OFF)
0.0001
-55 -35 -15
5
25 45
65
85 105 125
TEMPERATURE (°C)
Rail-to-Rail is a registered trademark of Nippon
Motorola Ltd.
20
Dual SPST/SPDT
analog switch fits
in 6-pin SOT23
The MAX4541–MAX4544 are a family
of dual, low-voltage analog switches. The
MAX4541/MAX4542/MAX4543 have
dual single-pole/single throw (SPST)
configurations: two normally open (NO)
switches (MAX4541), two normally
closed (NC) switches (MAX4542), and
one NO with one NC (MAX4543). The
MAX4544 offers an all-new singlepole/double-throw (SPDT) configuration
in a 6-pin SOT23 package.
Low power consumption (5µW) makes
these switches ideal for use in batterypowered equipment. They offer low
leakage current (100pA maximum at
+25°C and 2.5nA maximum at +85°C) and
fast switching: tON is 150ns (max), and
tOFF is 100ns (max). Low charge injection
is guaranteed at 5pC (max), and all
switches offer 2kV protection against ESD
per Method 3015.7 of MIL-STD-883.
All switches operate from a single
+2.7V to +12V supply. When operating
from a +5V supply, they exhibit 60Ω (max)
on-resistances (33Ω typical), 2Ω (max)
between-channel matching, and 6Ω (max)
RON flatness over the analog input range.
All control inputs are TTL/CMOS compatible, and the MAX4543/MAX4544 guarantee break-before-make switching.
For dual-supply operation, see the
MAX320/MAX321/MAX322 (pin compatible with the MAX4541/MAX4542/
MAX4543). For similar, quad versions
of these dual-supply switches, see
the MAX391/MAX392/MAX393. The
MAX4541–MAX4544 are available in 8-pin
DIP, µMAX, and SO packages; the
MAX4544 also offers a 6-pin SOT23
option. All are available in versions
specified for the commercial (0°C to +70°C)
or extended-industrial (-40°C to +85°C)
temperature range. Prices start at $0.41
(1000 up, FOB USA).
NEW PRODUCTS
Multiple-output
notebook powersupply controllers
are 96% efficient
modulation (PWM) mode that reduces
noise and RF interference in mobile
communications, pen-entry devices, and
other sensitive applications. The PWM
switching frequency can be synchronized to
an external signal, if necessary.
The MAX1630–MAX1635 switchmode power-supply controllers have stepdown (buck) topologies to generate logic
supply voltages in battery-powered
systems. They produce dual and triple
outputs plus many other functions: powerup sequencing, power-good signal with
delay, digital soft-start, secondary winding
control, low-dropout circuitry, internal
frequency-compensation networks, and
automatic bootstrapping.
The MAX1630/MAX1632/MAX1633/
MAX1635 contain 12V/120mA linear regulators. The MAX1631/MAX1634 lack the
12V regulator, but include a secondaryfeedback input (SECFB) and a control pin
(STEER) that selects which PWM loop
(3.3V or 5V) receives feedback from the
secondary. SECFB allows you to adjust
the secondary winding’s regulation point
with an external resistor divider, and helps
generate output voltages other than 12V.
Synchronous rectification and Maxim’s
proprietary Idle Mode™ control scheme
help to achieve conversion efficiencies as
high as 96%. High efficiency (>80%) over a
1000:1 load-current range extends battery
life in suspend mode, idle mode, and other
low-load conditions. The MAX1630–
MAX1635’s excellent dynamic response
corrects (to within five clock cycles at
300kHz) the output load transients caused
by the latest dynamic-clock CPUs. In
addition, the internal gate drivers’ robust
1A output capability ensures fast switching
for external n-channel MOSFETs.
The MAX1633/MAX1634/MAX1635,
which lack the output undervoltage
shutdown and overvoltage protection on
the MAX1630/MAX1631/MAX1632,
make it simpler to troubleshoot prototype
boards. They also serve applications in
which the outputs are supported by
external keep-alive supplies that would
otherwise interfere with the overvoltageprotection circuitry.
Input voltage range is 4.2V to 30V. At
12V, quiescent current is 250µA, dropping
to 4µA in shutdown mode. Each device
features a logic-controlled pulse-width-
Micropower linear
regulator accepts
inputs to 28V
The MAX1615 micropower linear
regulator is useful in all battery-powered
systems. It is designed to provide a pinselectable keep-alive supply of 5V or
3.3V (with ±2% initial output accuracy)
for CMOS RAM in a notebook computer.
The 4V to 28V input range allows direct
connection to high-voltage batteries.
Despite a miserly 8µA (max) no-load
supply current, the MAX1615 has excellent
AC PSRR and line-transient response,
providing clean 5V or 3.3V outputs even
when subjected to the fast supply-voltage
The MAX1630–MAX1635 are available in a 28-pin SSOP, in versions
specified for the commercial (0°C to
+70°C) or extended-industrial (-40°C to
+85°C) temperature range. Prices start at
$5.22 (1000 up, FOB USA).
Idle Mode is a trademark of Maxim Integrated
Products.
changes that occur when switching between
the battery and an AC adapter. The 30mA
(max) output current is guaranteed by
design. Dropout voltage is 350mV (max),
and shutdown supply current is less
than 1µA.
Fault protection includes internal
foldback-current limiting and thermalshutdown circuitry. The MAX1615 is
specified for the extended- 4V TO 28V
industrial temperature range (-40°C
to +85°C), and comes in a tiny 5-pin
SOT23 package, whose excellent SHDN
thermal characteristics tolerate
power dissipation to 571mW Prices
start at $0.79 (1000 up, FOB USA).
Dual, step-up
DC-DC controller is
smallest available
The MAX863 includes two independent, step-up DC-DC controllers on a single
IC in a 16-pin QSOP (same board area as an
8-pin SO). Each controller generates a highpower output by driving a low-cost external
n-channel MOSFET. The main output uses
Maxim’s proprietary Dual Mode™ feature
to provide 3.3V or 5V (or an adjustable
output) to power the system logic and
microprocessor. The second output, ideal for
powering PCMCIA cards or driving an
LCD, is adjustable with external resistors.
Input voltage range extends down to
1.5V to allow start-up and operation from
two or three battery cells (required in organizers, translators, and other low-power
hand-held products). A current-limited,
pulse-frequency-modulated (PFM) control
mode reduces start-up surges; for output
loads from 20mA to over 1A, it provides
efficiencies as high as 90%. With both
controllers operating, quiescent supply
current is 50µA. The MAX863 provides
independent 1µA shutdown controls for
system flexibility and long battery life.
For applications in which the input
voltage extends above and below the main
output voltage, the MAX863 can be configured in a buck/boost SEPIC topology. For
complex systems, two MAX863s can
generate 3.3V, 5V, 12V, and 28V.
The MAX863 is available in a 16-pin
QSOP specified for the extended-industrial
temperature range (-40°C to +85°C).
Prices start at $2.80 (1000 up, FOB USA).
An evaluation kit (MAX863EVKIT) is
also available; it includes the MAX863, an
assembled printed circuit card, and all
other external components required.
Dual Mode is a trademark of Maxim Integrated
Products.
IN
MAX1615
OUT
30mA
REF
POWERMANAGEMENT
MICROCONTROLLER
4.7µF
5/3
5V, 3.3V SELECT
21
CMOS RAM
RTC
NEW PRODUCTS
Step-up DC-DC
converter supplies
±28V for LCDs and
varactors
The MAX629 high-efficiency boost
converter produces a positive or negative
high-voltage output from low-voltage
inputs. It can drive the LCD in a small
hand-held system or the varactor tuner in
a set-top box. Its 30V internal switch (vs.
an external switch) saves space and cost.
The MAX629’s internal switch, low
supply current, small package, and tiny
external components provide an extremely
compact and efficient high-voltage supply
for LCDs.
High-performance
step-down
controllers power
high-end CPUs
The MAX1624/MAX1625 step-down
controllers are intended for demanding
applications in which output voltage
precision and good transient response are
essential for proper operation. Powered by
single +5V ±10% supplies, they deliver
more than 100W. Output accuracy over
line and load is better than ±1%.
Two external resistors program the
MAX1625 output voltage, and an internal
5-bit DAC enables the MAX1624 to
provide a digitally programmable output,
adjustable in 100mV increments from
1.1V to 3.5V. Both devices employ
synchronous rectification to achieve efficiencies greater than 90%. Flyingcapacitor bootstrap circuitry generates
gate-drive voltages higher than V CC ,
enabling the use of inexpensive
n-channel MOSFETs for both external
switching transistors.
Excellent dynamic response minimizes the output transients otherwise
induced by the latest dynamically clocked
CPUs, and external resistors program the
switching frequency from 100kHz to
1MHz. High frequencies eliminate the
need for large surface-mount inductors
and output filter capacitors, reducing
board area and system cost. Other features
A polarity-select pin, which inverts
the polarity of the feedback-error
amplifier and shifts the set point from
VREF to ground, allows the circuit to be
configured for a high positive or negative
output voltage. Typical input voltages
(3.3V or 5V) enable the MAX629 to
generate output voltages as high as ±28V
with 10mA output capability. VOUT can
be set with a resistor divider, potentiometer, or digital-to-analog converter
(DAC). This device requires a +2.7V to
+5.5V power supply, but power for the
step-up inductor can come directly from a
battery or any other voltage between 0.8V
and VOUT.
The MAX629’s current-limited, pulsefrequency-modulation control scheme
achieves efficiencies as high as 93% over a
wide range of load conditions. Its low
supply current (80µA during operation and
1µA during shutdown) is ideal for batterypowered applications. High switching
frequencies (to 300kHz) and a pinselectable 500mA or 250mA current limit
allow the use of tiny, inexpensive inductors.
common to both devices include an
internal digital soft-start, a power-good
output, and a 3.5V ±1% reference output.
The MAX1624 also allows user control
of the loop gain, to trade output accuracy
against the output filter-capacitor requirement. AC-load regulation can be set to
0.5%, 1%, or 2% by connecting the LG
input to ground, REF, or VCC.
The MAX629 is available in a small,
8-pin SO package specified for the
extended-industrial temperature range
(-40°C to +85°C). Prices start at $2.85
(1000 up, FOB USA).
When dynamically clocked CPUs
toggle their internal circuitry on and off to
save power, they can generate load steps
that are several amperes within a few tens
of nanoseconds. To minimize transients on
the supply rails for these CPUs, the
MAX1624 provides dedicated high-speed
outputs (NDRV and PDRV) for driving
external p-channel and n-channel
MOSFETs. These MOSFETs form a
Glitch-Catcher™ that quickly restores
regulation at VOUT by providing a brief
short to V + or ground, bypassing the
inductor’s lowpass-filter effect.
The MAX1625 is available in a 16-pin
narrow-SO package, and the MAX1624 is
available in a 24-pin SSOP. Both are
specified for the extended-industrial
temperature range (-40°C to +85°C).
Prices start at $3.85 (1000 up, FOB USA).
Glitch-Catcher is a trademark of Maxim
Integrated Products.
INPUT 5V
VCC
VDD
CSH
TO AGND
TO VDD
CSL
BST
PWRGOOD
DH
N
P
D/A
INPUTS
LX
MAX1624
DL
FREQ
VOUT
N
N
PGND
CC2
FB
CC1
REF
TO
AGND
AGND
PDRV
NDRV
(SIMPLIFIED)
22
GLITCH-CATCHER
NEW PRODUCTS
The MAX679 is available in an
1.11mm-high, 8-pin µMAX package (half
the size of an 8-pin SO), specified for the
extended-industrial temperature range
(-40°C to +85°C). Prices start at $1.55
(1000 up, FOB USA).
hungry heated references while consuming
relatively small amounts of power (18mW
typ). These devices achieve their exceptional temperature stability with a lowpower compensation scheme.
Low-noise,
precision voltage
references
guarantee 1ppm/°C
tempcos
Output voltages are fixed at 2.500V
(MAX6325), 4.096V (MAX6341), and
5.000V (MAX6350); with initial accuracies of ±0.02%. Each reference guarantees
its load-regulation specification for
source/sink currents to ±15mA. All three
devices include options for external
voltage trimming and noise reduction.
The MAX6325/MAX6341/MAX6350
precision voltage references feature low
noise and extremely low temperature coefficients (tempcos). Excellent line/load
regulation and low output impedance at
high frequencies make them ideal for use
in systems with digital resolution to
16 bits. The MAX6325 features a buriedzener technology that provides a very low
output noise of 1.5µVp-p (0.1Hz to 10Hz).
The MAX6325/MAX6341/MAX6350
come in 8-pin DIPs and SOs, in versions
screened for the commercial (0°C to
+70°C), extended-industrial (-40°C to
+85°C), or military (-55°C to +125°C)
temperature range. Prices start at $6.70
(1000 up, FOB USA).
Each reference exhibits the ultra-low
tempco (0.5ppm/°C typ, 1ppm/°C max)
normally associated with costly, power-
SE
O
EN
HE
AR
FT
ULTRA-LOW DRIFT
I
DR
ULTRA-LOW NOISE
0.3
120
0.2
80
0.1
40
0
0
-0.1
-40
-0.2
-80
-0.3
-120
-0.4
-40 -15
-160
5
25
45
65
0.1Hz to 10Hz OUTPUT NOISE
0.5µV/div
The MAX679 comes in an ultra-small
µMAX package and requires no external
inductor. Its low operating voltage and
high switching frequency (to 1MHz)
enable the use of very small surfacemount components: a small flying capacitor (0.33µF), a 4.7µF input capacitor,
and a 10µF output capacitor. The entire
circuit fits in less than 0.05in2. To prevent
battery drain, the MAX679 features a
logic-controlled shutdown that lowers the
supply current to 1µA and disconnects the
load. Special soft-start circuitry prevents
the flow of excessive battery current
during start-up.
The MAX3187 comes in a spacesaving 36-pin SSOP with flow-through
pinout, in versions specified for the
commercial (0°C to +70°C) or extendedindustrial (-40°C to +85°C) temperature
range. Prices start at $1.85 (100,000 up,
FOB USA).
OUTPUT-VOLTAGE CHANGE (ppm)
Operating in regulated doubler mode,
the MAX679 provides regulation by
gating the internal oscillator on and off,
increasing the number of cycles as the
load increases or the input supply voltage
decreases. As a limiting case, the charge
pump operates continuously at a pinselectable frequency (330kHz or 1MHz)
that allows a trade-off between quiescent
current and capacitor size. The MAX679’s
low operating current (50µA) provides
high efficiency (just under 90%) for the
following conditions: VIN = 2V, VOUT =
3.3V, and IOUT = 20mA.
The MAX3187 RS-232 transceiver
includes six drivers and ten receivers,
forming two complete DTE serial ports.
Each meets the European Community’s
stringent electrostatic-discharge (ESD)
requirements: all transmitter outputs and
receiver inputs are protected to ±15kV
using the Human Body Model or IEC
1000-4-2 Air-Gap-Discharge method, and
to ±8kV using the IEC 1000-4-2 ContactDischarge method. The chip remains
latchup free during ESD events.
85
1.00sec/div
TEMPERATURE (°C)
6325
The MAX679 DC-DC converter is a
charge-pump step-up device that provides
a regulated 3.3V (±4%) from 1.8V to
3.6V input voltages (as produced by two
alkaline, NiCd, or NiMH cells).
The MAX3187 is optimized for use in
motherboards and desktop PCs. Compatible with popular PC-communications
software, it is guaranteed for data rates as
high as 230kbps. It operates on +5V and
±12V nominal supply voltages, and draws
less than 3mA (I CC ) and 1mA (I DD
and ISS).
Dual, 230kbps
RS-232 serial
port (6 Tx/10 Rx)
withstands
±15kV ESD
OUTPUT-VOLTAGE CHANGE (mV)
Boost 2-cell
batteries to 3.3V;
no inductor needed
23
NO
NO
ISE
Was this manual useful for you? yes no
Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Download PDF

advertisement