MAXIM MAX4292

19-1612; Rev 0; 3/00
Ultra-Small, +1.8V, µPower,
Rail-to-Rail I/O Op Amps
Features
♦ Ultra-Low Voltage Operation—Guaranteed Down
to +1.8V
♦ 100µA Supply Current per Amplifier
♦ 500kHz Gain-Bandwidth Product
♦ 120dB Open-Loop Voltage Gain (RL = 100kΩ)
♦ 0.017% THD + Noise at 1kHz
♦ Rail-to-Rail Input Common-Mode Range
♦ Rail-to-Rail Output Drives 2kΩ Load
♦ No Phase Reversal for Overdriven Inputs
♦ Unity-Gain Stable for Capacitive Loads up to 100pF
♦ 400µV Input Offset Voltage
♦ Single Available in Ultra-Small 5-Pin SC70
Dual Available in Space-Saving 8-Pin µMAX
Applications
2-Cell Battery-Operated Systems
Ordering Information
PART
TEMP. RANGE
PINPACKAGE
TOP
MARK
Battery-Powered Instrumentation
MAX4291EXK-T
-40°C to +85°C
5 SC70-5
AAD
Digital Scales
MAX4291EUK-T
MAX4292EUA*
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
5 SOT23-5
8 µMAX
8 SO
ADML
—
—
-40°C to +85°C
-40°C to +85°C
14 SO
14 TSSOP
—
—
Portable Electronic Equipment
Strain Gauges
MAX4292ESA*
Sensor Amplifiers
MAX4294ESD*
Cellular Phones
MAX4294EUD*
*Future product—contact factory for availability.
Selector Guide
PART
AMPLIFIERS
PER PACKAGE
MAX4291
1
5-pin SC70/SOT23
MAX4292
2
8-pin µMAX/SO
MAX4294
4
14-pin SO/TSSOP
PIN-PACKAGE
Pin Configurations
TOP VIEW
IN+ 1
VEE 2
IN- 3
5 VCC
1
INA- 2
MAX4291
4 OUT
SC70-5/SOT23-5
Rail-to-Rail is a registered trademark of Nippon Motorola, Ltd.
OUTA
MAX4292
8
VCC
7
OUTB
INA+
3
6
INB-
VEE
4
5
INB+
µMAX/SO
Pin Configurations continued at end of data sheet.
________________________________________________________________ Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
MAX4291/MAX4292/MAX4294
General Description
The MAX4291/MAX4292/MAX4294 family of micropower operational amplifiers operates from a +1.8V to
+5.5V single supply or ±0.9V to ±2.75V dual supplies
and has Rail-to-Rail® input/output capabilities. These
amplifiers provide a 500kHz gain-bandwidth product
and 120dB open-loop voltage gain while using only
100µA of supply current per amplifier. The combination
of low input offset voltage (±400µV) and high-open-loop
gain makes them suitable for low-power/low-voltage
high-precision applications.
The MAX4291/MAX4292/MAX4294 have an input common-mode range that extends to each supply rail, and
their outputs typically swing within 20mV of the rails with
a 2kΩ load. Although the minimum operating voltage is
specified at +1.8V, these devices typically operate down
to +1.5V. The combination of ultra-low-voltage operation,
rail-to-rail inputs/output, and low-power consumption
makes these devices ideal for any portable/two-cell battery-powered system.
The single MAX4291 is offered in an ultra-small 5-pin
SC70 package and the dual MAX4292 is offered in a
space-saving 8-pin µMAX package.
MAX4291/MAX4292/MAX4294
Ultra-Small, +1.8V, µPower,
Rail-to-Rail I/O Op Amps
ABSOLUTE MAXIMUM RATINGS
Supply Voltage (VCC to VEE) ..................................................+6V
All Other Pins ...................................(VCC + 0.3V) to (VEE - 0.3V)
Output Short-Circuit Duration.....................................Continuous
Continuous Power Dissipation (TA = +70°C)
5-Pin SC70 (derate 2.5mW/°C above +70°C) ................200mW
5-Pin SOT23 (derate 7.1mW/°C above +70°C)................571mW
8-Pin µMAX (derate 4.10mW/°C above +70°C)..............330mW
8-Pin SO (derate 5.88mW/°C above +70°C) ..................471mW
14-Pin SO (derate 8.33mW/°C above +70°C) ................667mW
14-Pin TSSOP (derate 6.3mW/°C above +70°C) ............500mW
Operating Temperature Range............................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(VCC = +1.8V to +5.5V, VEE = VCM = 0, VOUT = VCC / 2, RL = 100kΩ connected to VCC / 2, TA = +25°C, unless otherwise noted.)
(Note 1)
PARAMETER
Supply Voltage Range
Quiescent Supply Current
(per Amplifier)
Input Offset Voltage
SYMBOL
VCC
IQ
VOS
CONDITIONS
TYP
MAX
UNITS
5.5
V
VCC = 1.8V
100
210
VCC = 5.0V
110
225
Inferred from PSRR test
MIN
1.8
MAX4291EXK, MAX4291EUK
±400
±2500
MAX4292EUA, MAX4294EUD
±400
±1500
MAX4292ESA, MAX4294ESD
±400
±1500
IB
VCC = 5.0V, 0 ≤ VCM ≤ 5.0V
±15
±55
Input Offset Current
IOS
VCC = 5.0V, 0 ≤ VCM ≤ 5.0V
±1
±7
Differential Input Resistance
RIN
|VIN+ - VIN-| < 10mV
Input Common-Mode Voltage
Range
VCM
Inferred from CMRR test
Input Bias Current
80
MAX4292EUA, MAX4294EUD
65
85
MAX4292ESA, MAX4294ESD
65
85
MAX4291EXK, MAX4291EUK
60
90
MAX4292EUA, MAX4294EUD
70
90
MAX4292ESA, MAX4294ESD
70
90
MAX4291EXK, MAX4291EUK
80
100
MAX4292EUA, MAX4294EUD
80
100
MAX4292ESA, MAX4294ESD
80
100
2
µV
nA
nA
MΩ
VCC
50
V
dB
CMRR
Tested for
0 ≤ VCM ≤
5.0V,
VCC = 5.0V
Power-Supply Rejection Ratio
0
MAX4291EXK, MAX4291EUK
Tested for
0 ≤ VCM ≤
1.8V;
VCC = 1.8V
Common-Mode Rejection Ratio
0.75
µA
PSRR
_______________________________________________________________________________________
dB
dB
Ultra-Small, +1.8V, µPower,
Rail-to-Rail I/O Op Amps
(VCC = +1.8V to +5.5V, VEE = VCM = 0, VOUT = VCC / 2, RL = 100kΩ connected to VCC / 2, TA = +25°C, unless otherwise noted.)
(Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
RL = 100kΩ,
0.015V ≤ VOUT ≤ VCC - 0.015V
80
120
RL = 2kΩ,
0.1V ≤ VOUT ≤ VCC - 0.1V
80
110
MAX
UNITS
VCC = 1.8V
Large-Signal Voltage Gain
AV
dB
RL = 100kΩ,
0.015V ≤ VOUT ≤ VCC - 0.015V
80
130
RL = 2kΩ,
0.1V ≤ VOUT ≤ VCC - 0.1V
80
120
VCC = 5.0V
Output Voltage Swing High
VOH
Specified as
|VCC – VOH|
Output Voltage Swing Low
VOL
Specified as
|VEE – VOL|
Output Short-Circuit Current
IOUT(SC)
Channel-to-Channel Isolation
CHISO
GBW
Gain Bandwidth Product
RL = 100kΩ to VCC / 2
2
20
RL = 2kΩ to VCC / 2
15
40
RL = 100kΩ to VCC / 2
3
15
RL = 2kΩ to VCC / 2
18
40
mV
mV
Sourcing or sinking
20
Specified at f = 10kHz (MAX4292/MAX4294 only)
100
mA
dB
500
kHz
degrees
Phase Margin
φM
65
Gain Margin
GM
12
dB
Slew Rate
SR
0.2
V/µs
Input Voltage Noise Density
en
f = 10kHz
70
nV/√Hz
Input Current Noise Density
in
f = 10kHz
0.05
pA/√Hz
AVCL = +1V/V, no sustained oscillations
100
pF
Capacitive-Load Stability
ELECTRICAL CHARACTERISTICS
(VCC = +1.8V to +5.5V, VEE = VCM = 0, VOUT = VCC / 2, RL = 100kΩ connected to VCC / 2, TA = TMIN to TMAX, unless otherwise
noted.) (Note 1)
PARAMETER
Supply Voltage Range
Quiescent Supply Current
(per Amplifier)
Input Offset Voltage
SYMBOL
VCC
IQ
VOS
CONDITIONS
Inferred from PSRR test
MIN
1.8
TYP
MAX
UNITS
5.5
V
VCC = 1.8V
240
VCC = 5.0V
270
MAX4291EXK, MAX4291EUK
±3000
MAX4292EUA, MAX4294EUD
±1500
MAX4292ESA, MAX4294ESD
±1500
µA
µV
_______________________________________________________________________________________
3
MAX4291/MAX4292/MAX4294
ELECTRICAL CHARACTERISTICS
MAX4291/MAX4292/MAX4294
Ultra-Small, +1.8V, µPower,
Rail-to-Rail I/O Op Amps
ELECTRICAL CHARACTERISTICS
(VCC = +1.8V to +5.5V, VEE = VCM = 0, VOUT = VCC / 2, RL = 100kΩ connected to VCC / 2, TA = TMIN to TMAX, unless otherwise
noted.) (Note 1)
PARAMETER
Input Offset Voltage Drift
SYMBOL
CONDITIONS
MIN
TCVOS
TYP
MAX
1.2
UNITS
µV/°C
IB
VCC = 5.0V, 0 ≤ VCM ≤ 5.0V
±80
nA
Input Offset Current
IOS
VCC = 5.0V, 0 ≤ VCM ≤ 5.0V
±10
nA
Input Common-Mode Voltage
Range
VCM
Inferred from CMRR test
0
VCC
V
MAX4291EXK, MAX4291EUK
Tested for
0 ≤ VCM ≤ 1.8V, MAX4292EUA, MAX4294EUD
VCC = 1.8V
MAX4292ESA, MAX4294ESD
50
MAX4291EXK, MAX4291EUK
Tested for
0 ≤ VCM ≤ 5.0V, MAX4292EUA, MAX4294EUD
VCC = 5.0V
MAX4292ESA, MAX4294ESD
60
MAX4291EXK, MAX4291EUK
78
MAX4292EUA, MAX4294EUD
80
MAX4292ESA, MAX4294ESD
MAX4292ESA, MAX4294ESD
80
Input Bias Current
Common-Mode Rejection Ratio
Power-Supply Rejection Ratio
CMRR
PSRR
VCC = 1.8V
Large-Signal Voltage Gain
AV
VCC = 5.0V
60
dB
60
65
dB
65
RL = 100kΩ,
0.015V ≤ VOUT ≤ VCC - 0.015V
80
RL = 2kΩ,
0.1V ≤ VOUT ≤ VCC - 0.1V
80
RL = 100kΩ,
0.015V ≤ VOUT ≤ VCC - 0.015V
80
RL = 2kΩ,
0.1V ≤ VOUT ≤ VCC - 0.1V
80
dB
dB
Output Voltage Swing High
VOH
Specified as
|VCC – VOH|
RL = 100kΩ to VCC / 2
20
RL = 2kΩ to VCC / 2
40
Output Voltage Swing Low
VOL
Specified as
|VEE – VOL|
RL = 100kΩ to VCC / 2
15
RL = 2kΩ to VCC / 2
40
Note 1: All devices are 100% tested at TA = +25°C. All temperature limits are guaranteed by design.
4
_______________________________________________________________________________________
mV
mV
Ultra-Small, +1.8V, µPower,
Rail-to-Rail I/O Op Amps
SUPPLY CURRENT PER AMPLIFIER
vs. TEMPERATURE
VCC = 5.5V
120
110
100
90
VCC = 1.8V
80
70
1.7
1.6
1.5
1.4
1.3
1.2
-150
VCC = 5.5V
-300
-450
VCC = 2.4V
-600
VCC = 1.8V
-750
1.0
-900
-55 -40 -25 -10 5 20 35 50 65 80 95 110 125
-55 -40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
INPUT BIAS CURRENT
vs. TEMPERATURE
INPUT BIAS CURRENT vs. COMMON-MODE
VOLTAGE (VCC = 1.8V)
INPUT BIAS CURRENT vs. COMMON-MODE
VOLTAGE (VCC = 5.5V)
VCC = 5.5V
15
VCC = 1.8V
5
20
10
0
-10
-20
-30
0
MAX4291 toc06
-10
-20
0
0.5
1.0
1.5
2.0
2.5
-0.5
0.5
1.5
2.5
3.5
4.5
COMMON-MODE VOLTAGE (V)
COMMON-MODE VOLTAGE (V)
OUTPUT VOLTAGE SWING vs.
TEMPERATURE (RL = 100kΩ to VCC / 2)
OUTPUT VOLTAGE SWING vs.
TEMPERATURE (RL = 2kΩ to VCC / 2)
COMMON-MODE REJECTION
RATIO vs. TEMPERATURE
VOL (VCC = 5.5V)
1.5
VOH (VCC = 5.5V)
VOL (VCC = 1.8V)
VOH (VCC = 1.8V)
35
30
VOH = VCC - VOUT
VOL = VOUT - VEE
VOL (VCC = 5.5V)
-75
VOL (VCC = 1.8V)
20
VOH (VCC = 5.5V)
15
10
VOH (VCC = 1.8V)
0 ≤ VCM ≤ VCC
VCC = 1.8V
-80
-85
VCC = 5.5V
-90
-95
-100
0
0.0
5.5
-70
25
5
0.5
-65
CMRR (dB)
VOH = VCC - VOUT
VOL = VOUT - VEE
2.0
1.0
0
-40
-0.5
OUTPUT VOLTAGE SWING (mV)
2.5
10
TEMPERATURE (°C)
MAX4291 toc07
3.0
20
-30
-40
-55 -40 -25 -10 5 20 35 50 65 80 95 110 125
3.5
30
MAX4291 toc09
20
40
INPUT BIAS CURRENT (nA)
25
-55 -40 -25 -10 5 20 35 50 65 80 95 110 125
MAX4291 toc05
30
INPUT BIAS CURRENT (nA)
30
10
40
MAX4291 toc04
35
OUTPUT VOLTAGE SWING (mV)
MAX4291 toc03
1.8
1.1
60
INPUT BIAS CURRENT (nA)
1.9
0
INPUT OFFSET VOLTAGE (µV)
130
2.0
MAX4291 toc08
SUPPLY CURRENT (µA)
140
INPUT OFFSET VOLTAGE
vs. TEMPERATURE
MAX4291 toc02
150
MINIMUM OPERATING VOLTAGE (V)
MAX4291 toc01
160
MINIMUM OPERATING VOLTAGE
vs. TEMPERATURE (PSRR ≥80dB)
-105
-55 -40 -25 -10 5 20 35 50 65 80 95 110 125
-55 -40 -25 -10 5 20 35 50 65 80 95 110 125
-55 -40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
_______________________________________________________________________________________
5
MAX4291/MAX4292/MAX4294
Typical Operating Characteristics
(VCC = +2.4V, VEE = VCM = 0, VOUT = VCC / 2, no load, TA = +25°C, unless otherwise noted.)
Ultra-Small, +1.8V, µPower,
Rail-to-Rail I/O Op Amps
MAX4291/MAX4292/MAX4294
Typical Operating Characteristics (continued)
(VCC = +2.4V, VEE = VCM = 0, VOUT = VCC / 2, no load, TA = +25°C, unless otherwise noted.)
RL = 1kΩ
110
RL = 2kΩ
110
RL = 1kΩ
130
110
RL = 1kΩ
GAIN (dB)
GAIN (dB)
90
90
80
100
90
80
80
70
70
60
60
50
50
50 100 150 200 250 300 350 400 450 500
70
60
50
0
50 100 150 200 250 300 350 400 450 500
VOL (mV)
120
RL = 1kΩ
MAX4291 toc14
RL = 2kΩ
120
110
OPEN-LOOP GAIN (dB)
100
90
80
100
RL = 2kΩ TO VCC
80
70
70
60
60
VCC = 5.5V
50
50 100 150 200 250 300 350 400 450 500
-55 -40 -25 -10 5 20 35 50 65 80 95 110 125
VOH (mV)
TEMPERATURE (°C)
GAIN AND PHASE vs. FREQUENCY
(CL = 0)
MAX4291 toc15
MAX4291 toc16
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
60
50
144
50
144
40
108
40
108
30
72
30
72
20
36
20
36
10
0
0
-36
-10
-72
-20
-30
-40
100
FREQUENCY (kHz)
1000
GAIN (dB)
180
AV = +1000V/V
PHASE (DEGREES)
GAIN (dB)
60
GAIN AND PHASE vs. FREQUENCY
(CL = 100pF)
AV = +1000V/V
0
10
0
-36
-10
-72
-108
-20
-108
-144
-30
-144
-180
-40
-180
0.1
1
10
100
FREQUENCY (kHz)
1000
1
180
THD + NOISE (%)
0
6
RL = 1kΩ TO VCC
90
50
10
RL = 1kΩ TO VEE
RL = 2kΩ TO VEE
MAX4291 toc18
110
OPEN-LOOP GAIN vs. TEMPERATURE
130
MAX4191 toc13
130
1
50 100 150 200 250 300 350 400 450 500
VOL (mV)
OPEN-LOOP GAIN vs. OUTPUT SWING HIGH
(VCC = +5.5V, RL CONNECTED TO VEE)
GAIN (dB)
0
VOH (mV)
PHASE (DEGREES)
0
0.1
RL = 2kΩ
120
100
100
GAIN (dB)
OPEN-LOOP GAIN vs. OUTPUT SWING LOW
(VCC = +5.5V, RL CONNECTED TO VCC)
MAX4291 toc11
RL = 2kΩ
120
120
MAX4291 toc10
130
OPEN-LOOP GAIN vs. OUTPUT SWING HIGH
(VCC = +1.8V, RL CONNECTED TO VEE)
MAX4191 toc12
OPEN-LOOP GAIN vs. OUTPUT SWING LOW
(VCC = +1.8V, RL CONNECTED TO VCC)
RL = 2kΩ
Av = +1V/V
(NONINVERTING
CONFIGURATION)
0.1
VCC = +5.5V
VCC = +1.8V
0.01
0.01
0.1
1
FREQUENCY (kHz)
_______________________________________________________________________________________
10
100
Ultra-Small, +1.8V, µPower,
Rail-to-Rail I/O Op Amps
SMALL-SIGNAL TRANSIENT RESPONSE
(NONINVERTING CONFIGURATION)
LOAD RESISTOR vs. CAPACITIVE LOAD
10% OVERSHOOT
AV = +1V/V
(NONINVERTING CONFIGURATION)
MAX4291 toc19
MAX4291 toc20
100
MAX4291 toc21
VCC = +2.5V
VEE = -2.5V 100mV
VCM = 0
VCC = +2.5V
VEE = -2.5V
VCM = 0
100mV
10
IN
IN
0
0
100mV
100mV
VCC = 5.5V
1
VCC = 2.4V
0.1
IOUT > 20mA
VCC = 5.5V
OUT
IOUT > 20mA
VCC = 2.4V
OUT
0
0
0.01
3
4
5
6
7
8
9
1µs/div
10
1µs/div
CAPACITIVE LOAD (nF)
LARGE-SIGNAL TRANSIENT RESPONSE
(NONINVERTING CONFIGURATION)
LARGE-SIGNAL TRANSIENT RESPONSE
(INVERTING CONFIGURATION)
MAX4291 toc22
VCC = +2.5V
VEE = -2.5V
VCM = 0
MAX4291 toc23
VCC = +2.5V
VEE = -2.5V
VCM = 0
+2V
IN
+2V
IN
-2V
-2V
+2V
+2V
OUT
OUT
-2V
-2V
10µs/div
10µs/div
SUPPLY CURRENT vs. SINK CURRENT
3000
2500
SUPPLY CURRENT vs. SOURCE CURRENT
150
VCC = 5.5V
2000
1500
VCC = 2.4V
1000
MAX4291/2/4-25
2
135
120
SUPPLY CURRENT (µA)
1
MAX4291/2/4-24
0
SUPPLY CURRENT (µA)
LOAD RESISTOR (kΩ)
SMALL-SIGNAL TRANSIENT RESPONSE
(INVERTING CONFIGURATION)
VCC = 5.5V
105
VCC = 2.4V
90
75
60
45
VCC = 1.8V
30
500
VCC = 1.8V
15
0
0
0
5
10
15
20
SINK CURRENT (mA)
25
30
0
5
10
15
20
25
SOURCE CURRENT (mA)
_______________________________________________________________________________________
7
MAX4291/MAX4292/MAX4294
Typical Operating Characteristics (continued)
(VCC = +2.4V, VEE = VCM = 0, VOUT = VCC / 2, no load, TA = +25°C, unless otherwise noted.)
MAX4291/MAX4292/MAX4294
Ultra-Small, +1.8V, µPower,
Rail-to-Rail I/O Op Amps
Pin Description
PIN
NAME
FUNCTION
MAX4291
MAX4292
MAX4294
1
–
–
IN+
Noninverting Input
2
4
11
VEE
Negative Supply. Connect to ground for single-supply operation.
3
–
–
IN-
Inverting Input
4
–
–
OUT
Amplifier Output
5
8
4
VCC
Positive Supply
–
1, 7
1, 7
OUTA, OUTB
–
2, 6
2, 6
INA-, INB-
–
3, 5
3, 5
INA+, INB+
–
–
8, 14
OUTC, OUTD
–
–
9, 13
INC-, IND-
–
–
10, 12
INC+, IND+
Outputs for Amplifiers A and B
Inverting Inputs to Amplifiers A and B
Noninverting Inputs to Amplifiers A and B
Outputs for Amplifiers C and D
Inverting Inputs to Amplifiers C and D
Noninverting Inputs to Amplifiers C and D
Detailed Description
Rail-to-Rail Input Stage
The MAX4291/MAX4292/MAX4294 have rail-to-rail
inputs and output stages that are specifically designed
for low-voltage, single-supply operation. The input
stage consists of separate NPN and PNP differential
stages, which operate together to provide a commonmode range extending to both supply rails. The
crossover region of these two pairs occurs halfway
between VCC and VEE. The input offset voltage is typically ±400µV. Low operating supply voltage, low supply current, rail-to-rail common-mode input range, and
rail-to-rail outputs make this family of operational amplifiers (op amps) an excellent choice for precision or
general-purpose, low-voltage, battery-powered systems.
Since the input stage consists of NPN and PNP pairs,
the input bias current changes polarity as the commonmode voltage passes through the crossover region.
Match the effective impedance seen by each input to
reduce the offset error caused by input bias currents
flowing through external source impedances (Figures
1a and 1b).
The combination of high source impedance plus input
capacitance (amplifier input capacitance plus stray
capacitance) creates a parasitic pole that produces an
underdamped signal response. Reducing input capacitance or placing a small capacitor across the feedback
resistor improves response in this case.
8
MAX4291
MAX4292
MAX4294
IN
R3
R3 = R1
R2
R1
R2
Figure 1a. Minimizing Offset Error Due to Input Bias Current
(Noninverting)
MAX4291
MAX4292
MAX4294
R3
R3 = R1
R2
IN
R1
R2
Figure 1b. Minimizing Offset Error Due to Input Bias Current
(Inverting)
_______________________________________________________________________________________
Ultra-Small, +1.8V, µPower,
Rail-to-Rail I/O Op Amps
VEND-OF-LIFE (V)
CAPACITY, AA SIZE
(mA-h)
MAX4291
OPERATING TIME IN
NORMAL MODE
(h)
3.0
1.8
2000
20,000
Yes
2.4
1.8
750
7500
Lithium-Ion
(1 cell)
Yes
3.5
2.7
1000
10,000
Nickel-MetalHydride (2 cells)
Yes
2.4
1.8
1000
10,000
BATTERY TYPE
RECHARGEABLE
VFRESH
(V)
Alkaline (2 cells)
No
Nickel-Cadmium
(2 cells)
IBIAS =
IN+
10.6k
(VDIFF - 1.8V)
21.2kΩ
In the region where the differential input voltage
approaches 1.8V, the input resistance decreases exponentially from 0.75MΩ to 21.2kΩ as the diode block
begins to conduct. Conversely, the bias current
increases with the same curve.
IN-
In unity-gain configuration, high slew rate input signals
may capacitively couple to the output through the triplediode stacks.
10.6k
Figure 2. Input Protection Circuit
Rail-to-Rail Output Stage
VCC = +2.5V, VEE = -2.5V
IN
2.5V/div
0
OUT
2.5V/div
0
The MAX4291/MAX4292/MAX4294 output stage can
drive up to a 2kΩ load and still swing to within 20mV of
the rails. Figure 3 shows the output voltage swing of a
MAX4291 configured as a unity-gain buffer, powered
from a ±2.5V supply. The output for this setup typically
swings from (VEE + 3mV) to (VCC - 2mV) with a 100kΩ
load.
Applications Information
Power-Supply Considerations
20µs/div
Figure 3. Rail-to-Rail Input/Output Voltage Range
The MAX4291/MAX4292/MAX4294 family’s inputs are
protected from large differential input voltages by internal 10.6kΩ series resistors and back-to-back triplediode stacks across the inputs (Figure 2). For
differential input voltages (much less than 1.8V), input
resistance is typically 0.75MΩ. For differential input
voltages greater than 1.8V, input resistance is around
21.2kΩ, and the input bias current can be approximated by the following equation:
The MAX4291/MAX4292/MAX4294 operate from a single +1.8V to +5.5V supply (or dual ±0.9V to ±2.75V
supplies) and consume only 100µA of supply current
per amplifier. A high power-supply rejection ratio of
80dB allows the amplifiers to be powered directly off a
decaying battery voltage, simplifying design and
extending battery life.
The MAX4291/MAX4292/MAX4294 are ideally suited for
use with most battery-powered systems. Table 1 lists a
variety of typical battery types showing voltage when
fresh, voltage at end-of-life, capacity, and approximate
operating time from a MAX4291 (assuming nominal
conditions).
_______________________________________________________________________________________
9
MAX4291/MAX4292/MAX4294
Table 1. MAX4291 Characteristics with Typical Battery Systems
OUTPUT SOURCE CURRENT
vs. TEMPERATURE
OFFSET VOLTAGE vs. SUPPLY VOLTAGE
-450
-550
TA = +25°C
-600
TA = -40°C
-650
VCC = 5.5V
VOH = 200mV
25
OUTPUT SOURCE CURRENT (mA)
-500
OFFSET VOLTAGE (µV)
30
VCM = VCC/2
TA = +85°C
15
10
0
-55 -40 -25 -10 5 20 35 50 65 80 95 110 125
SUPPLY VOLTAGE (V)
TEMPERATURE (°C)
Figure 4. Offset Voltage vs. Supply Voltage
Figure 6a. Output Source Current vs. Temperature
OUTPUT SINK CURRENT
vs. TEMPERATURE
SUPPLY CURRENT vs. SUPPLY VOLTAGE
140
18
VOL = VOUT - VEE
VCC = 5.5V
VOL = 200mV V = 5.5V
CC
VOL = 50mV
VCC = 1.8V
VOL = 200mV
VCC = 5.5V
VOL = 100mV
VCC = 1.8V
VOL = 100mV VCC = 1.8V
VOL = 50mV
16
100
80
TA = +25°C
TA = -40°C
TA = +85°C
20
OUTPUT SINK CURRENT (mA)
120
40
VCC = 1.8V
VOH = 200mV
5
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5
60
VOH = VCC - VOUT
VCC = 5.5V
VOH = 100mV
VCC = 5.5V
VOH = 50mV VCC = 1.8V
VOH = 100mV VCC = 1.8V
VOH = 50mV
20
-700
SUPPLY CURRENT (µA)
MAX4291/MAX4292/MAX4294
Ultra-Small, +1.8V, µPower,
Rail-to-Rail I/O Op Amps
14
12
10
8
6
4
2
0
0 0.5 1 1.5 2 2.5 3 3.5
4 4.5 5 5.5
0
-55 -40 -25 -10 5 20 35 50 65 80 95 110 125
SUPPLY VOLTAGE (V)
TEMPERATURE (°C)
Figure 5. Supply Current vs. Supply Voltage
Figure 6b. Output Sink Current vs. Temperature
Although the amplifiers are fully guaranteed over temperature for operation down to a +1.8V single supply,
even lower voltage operation is possible in practice.
Figures 4 and 5 show the offset voltage and supply current as a function of supply voltage and temperature.
Figures 6a and 6b show the typical current source and
sink capabilities of the MAX4291/MAX4292/MAX4294
family as a function of supply voltage and ambient temperature. The contours on the graph depict the output
current value, based on driving the output voltage to
within 50mV, 100mV, and 200mV of either power-supply rail.
For example, a MAX4291 running from a single +1.8V
supply, operating at TA = +25°C can source 3.5mA to
within 100mV of VCC and is capable of driving a 485Ω
load resistor to VEE:
Load-Driving Capability
The MAX4291/MAX4292/MAX4294 are fully guaranteed
over temperature and supply voltage range to drive a
maximum resistive load of 2kΩ to V CC /2, although
heavier loads can be driven in many applications. The
rail-to-rail output stage of the amplifier can be modeled
as a current source when driving the load toward VCC,
and as a current sink when driving the load toward VEE.
The limit of this current source/sink varies with supply
voltage, ambient temperature, and lot-to-lot variations
of the units.
10
RL =
(1.8V − 0.1V)
= 485Ω to VEE
3.5mA
The same application can drive a 220kΩ load resistor
when terminated in VCC/2 (+0.9V in this case).
______________________________________________________________________________________
Ultra-Small, +1.8V, µPower,
Rail-to-Rail I/O Op Amps
IN
RISO
0
OUT
IN
MAX4240
MAX4241
MAX4242
MAX4243
MAX4244
RL
CL
100mV
OUT
0
AV =
RL
≈1
RL + RISO
Figure 7a. Using a Resistor to Isolate a Capacitive Load from
the Op Amp
10µs/div
VCC = +2.4V, RL = 2kΩ TO VEE, CL = 1000pF, RISO = 100Ω
Figure 7c. Pulse Response with Isolating Resistor (100 Ω)
and the VEE supplies should be bypassed to ground
with separate 100nF capacitors.
100mV
IN
0
100mV
OUT
0
10µs/div
VCC = +2.4V, RL = 2kΩ TO VEE, CL = 1000pF
Figure 7b. Pulse Response Without Isolating Resistor
Driving Capacitive Loads
The MAX4291/MAX4292/MAX4294 are unity-gain stable
for loads up to 100pF (see the Load Resistor vs.
Capacitive Load graph in the Typical Operating
Characteristics). Applications that require greater
capacitive drive capability should use an isolation
resistor between the output and the capacitive load
(Figure 7). Note that this alternative results in a loss of
gain accuracy because RISO forms a voltage divider
with the load resistor.
Power-Supply Bypassing and Layout
The MAX4291/MAX4292/MAX4294 family operates from
either a single +1.8V to +5.5V supply or dual ±0.9V to
±2.75V supplies. For single-supply operation, bypass
the power supply with a 100nF capacitor to VEE (in this
case GND). For dual-supply operation, both the VCC
Good PC board layout techniques optimize performance by decreasing the amount of stray capacitance
at the op amp’s inputs and output. To decrease stray
capacitance, minimize trace lengths and widths by
placing external components as close as possible to
the op amp. Surface-mount components are an excellent choice.
Using the MAX4291/MAX4292/MAX4294
as Comparators
Although optimized for use as operational amplifiers,
the MAX4291/MAX4292/MAX4294 can also be used as
rail-to-rail I/O comparators. Typical propagation delay
depends on the input overdrive voltage, as shown in
Figure 8. External hysteresis can be used to minimize
the risk of output oscillation. The positive feedback circuit, shown in Figure 9, causes the input threshold to
change when the output voltage changes state. The
two thresholds create a hysteresis band that can be
calculated by the following equations:
V
HYST
=V
HI
−V
LO

R1
R1 
V = 1 +
+
V
HI 
R2 R
 REF
HYST 

 R1 
V =V −
 V
LO
HI  R
 CC
 HYST 
When the output of the comparator is low, the supply
current increases. The output stage has biasing circuitry to monitor the output current. When the amplifier is
______________________________________________________________________________________
11
MAX4291/MAX4292/MAX4294
100mV
PROPAGATION DELAY
vs. INPUT OVERDRIVE
1000
HYSTERESIS
VHI
INPUT
VLO
VOH
tPD+, VCC = 5.5V
OUTPUT
VOL
tPD (µs)
VSIG
tPD-, VCC = 5.5V
100
RHYST
R1
tPD-, VCC = 1.8V
tPD+, VCC = 1.8V
VCC
VOUT
MAX4291
R2
VREF
10
0
10 20 30 40 50 60
VEE = GND MAX4292
MAX4294
70 80 90 100
VEE = GND
VOD (mV)
Figure 8. Propagation Delay vs. Input Overdrive
used as a comparator, the output stage is overdriven
and the current through the biasing circuitry increases
to maximum. For the MAX4291, typical supply currents
increase to 1.5mA with VCC = 1.8V and to 9mA when
VCC = 5.0V (Figure 10).
Using the MAX4291/MAX4292/MAX4294
as Low-Power Current Monitors
The MAX4291/MAX4292/MAX4294 are ideal for applications powered from a two-cell battery stack. Figure
11 shows an application circuit in which the MAX4291
is used for monitoring the current of a two-cell battery
stack. In this circuit, a current load is applied, and the
voltage drop at the battery terminal is sensed.
The voltage on the load side of the battery stack is
equal to the voltage at the emitter of Q1 due to the
feedback loop containing the op amp. As the load current increases, the voltage drop across R1 and R2
increases. Thus, R2 provides a fraction of the load current (set by the ratio of R1 and R2) that flows into the
emitter of the PNP transistor. Neglecting PNP base current, this current flows into R3, producing a ground-referenced voltage proportional to the load current. To
minimize errors, scale R1 to give a voltage drop that is
large enough in comparison to the op amp’s VOS.
Figure 9. Hysteresis Comparator Circuit
MAXIMUM SUPPLY CURRENT
vs. SUPPLY VOLTAGE
12
MAXIMUM SUPPLY CURRENT (mA)
MAX4291/MAX4292/MAX4294
Ultra-Small, +1.8V, µPower,
Rail-to-Rail I/O Op Amps
10
COMPARATOR CONFIGURATION
VIN+ = (VIN-) - 100mV
8
6
4
2
0
0 0.5 1 1.5 2 2.5 3 3.5
4 4.5 5 5.5
SUPPLY VOLTAGE (V)
Figure 10. Maximum Supply Current vs. Supply Voltage
Calculate the output voltage of the application using
the following equation:

 R1  
VOUT = ILOAD ×    × R3
 R2  

For a 1V output and a current load of 50mA, the choice
of resistors can be R1 = 2Ω, R2 = 100kΩ, and R3 =
1MΩ.
12
______________________________________________________________________________________
Ultra-Small, +1.8V, µPower,
Rail-to-Rail I/O Op Amps
R1
TOP VIEW
VCC
R2
OUTA 1
INA- 2
Q1
VOUT
R3
MAX4291
VEE
Figure 11. Current Monitor for a 2-Cell Battery Stack
14 OUTD
MAX4294
13 IND-
INA+ 3
12 IND+
VCC 4
11 VEE
INB+ 5
10 INC+
INB- 6
9 INC-
OUTB 7
8 OUTC
TSSOP/SO
Chip Information
MAX4291 TRANSISTOR COUNT: 149
MAX4292 TRANSISTOR COUNT: 356
MAX4294 TRANSISTOR COUNT: 747
______________________________________________________________________________________
13
MAX4291/MAX4292/MAX4294
Pin Configurations (continued)
ILOAD
Ultra-Small, +1.8V, µPower,
Rail-to-Rail I/O Op Amps
SOT5L.EPS
SC70, 5L.EPS
MAX4291/MAX4292/MAX4294
Package Information
14
______________________________________________________________________________________
Ultra-Small, +1.8V, µPower,
Rail-to-Rail I/O Op Amps
8LUMAXD.EPS
SOICN.EPS
Note: The MAX4292 does not have an exposed pad.
______________________________________________________________________________________
15
MAX4291/MAX4292/MAX4294
Package Information (continued)
Ultra-Small, +1.8V, µPower,
Rail-to-Rail I/O Op Amps
TSSOP.EPS
MAX4291/MAX4292/MAX4294
Package Information (continued)
Note: The MAX4294 does not have an exposed pad.
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
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Printed USA
is a registered trademark of Maxim Integrated Products.