19-1612; Rev 3; 4/02
Ultra-Small, 1.8V, µPower,
Rail-to-Rail I/O Op Amps
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 (±200µV) and high open-loop gain makes
them ideal for low-power/low-voltage, high-precision
portable applications.
The MAX4291/MAX4292/MAX4294 have an input common-mode range that extends to each supply rail, and
their outputs swing to within 46mV 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, railto-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. The dual MAX4292 is offered in a
space-saving 8-bump, 1.5mm X 1.5mm footprint, ultra
chip-scale package (UCSP™).
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% Total Harmonic Distortion Plus Noise
(THD + N) 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
♦ 200µV Input Offset Voltage (MAX4292/MAX4294)
♦ Single in Small 5-Pin SC70
♦ Available in Ultra-Small Packages:
5-Pin SC70 (MAX4291)
8-Bump UCSP (MAX4292)
Ordering Information
Applications
MAX4291EXK-T
-40°C to +85°C
PINPACKAGE
5 SC70-5
Battery-Powered Instrumentation
MAX4291EUK-T
-40°C to +85°C
5 SOT23-5
ADML
Digital Scales
MAX4292EBL-T*
-40°C to +85°C
8 UCSP-8
AAJ
Strain Gauges
MAX4292EUA
-40°C to +85°C
8 µMAX
—
—
2-Cell Battery-Operated Systems
Portable Electronic Equipment
PART
TEMP RANGE
TOP
MARK
AAD
Sensor Amplifiers
MAX4292ESA
-40°C to +85°C
8 SO
Cellular Phones
MAX4294ESD
-40°C to +85°C
14 SO
—
MAX4294EUD
-40°C to +85°C
14 TSSOP
—
Pin Configurations
TOP VIEW
(BUMPS ON BOTTOM)
OUTA
VCC
OUTB
INA-
MAX4292
INB-
*UCSP reliability is integrally linked to the user’s assembly
methods, circuit board material, and environment. Refer to the
UCSP Reliability Notice in the UCSP Reliability section of this
data sheet for more information.
Selector Guide
PART
INA+
VEE
INB+
AMPLIFIERS
PIN-PACKAGE
MAX4291
1
5-pin SC70/SOT23
MAX4292
2
8-pin µMAX/SO/UCSP
MAX4294
4
14-pin SO/TSSOP
UCSP
Pin Configurations continued at end of data sheet.
Rail-to-Rail is a registered trademark of Nippon Motorola, Ltd.
UCSP is a trademark of Maxim Integrated Products, Inc.
________________________________________________________________ Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1
MAX4291/MAX4292/MAX4294
General Description
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)
Current into IN_+, IN_- .....................................................±25mA
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-Bump UCSP (derate 4.7mW/°C above +70°C) ...........379mW
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
TYP
MAX
UNITS
5.5
V
VCC = 1.8V
100
210
VCC = 5.0V
100
255
MAX4291
±400
±2500
MAX4292/MAX4294
±200
±1200
IB
VCC = 5.0V, 0 ≤ VCM ≤ 5.0V
±15
±60
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
0
Tested for
0 ≤ VCM ≤
1.8V;
VCC = 1.8V
MAX4291
50
80
MAX4292/MAX4294
57
80
MAX4291
60
90
Supply Voltage Range
Quiescent Supply Current
(Per Amplifier)
Input Offset Voltage
Input Bias Current
Common-Mode Rejection Ratio
SYMBOL
VCC
IQ
VOS
2
Inferred from PSRR test
MIN
1.8
0.75
µA
µV
nA
nA
MΩ
VCC
V
dB
CMRR
Tested for
0 ≤ VCM ≤
5.0V,
VCC = 5.0V
Common-Mode Rejection Ratio
Power-Supply Rejection Ratio
CONDITIONS
PSRR
dB
MAX4292/MAX4294
66
90
77
100
_______________________________________________________________________________________
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,
0.02V ≤ VOUT ≤ VCC - 0.02V
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,
0.02V ≤ VOUT ≤ VCC - 0.02V
80
130
RL = 2kΩ,
0.1V ≤ VOUT ≤ VCC - 0.1V
80
120
VCC = 5.0V
Output-Voltage Swing High
VOH
Specified as
|VCC - VOH|
RL = 100kΩ to VCC/2
2
20
RL = 2kΩ to VCC/2
15
40
Output-Voltage Swing Low
VOL
Specified as
|VEE - VOL|
RL = 100kΩ to VCC/2
25
80
RL = 2kΩ to VCC/2
46
120
Output Short-Circuit Current
IOUT(SC)
Channel-to-Channel Isolation
CHISO
Gain-Bandwidth Product
mV
mV
Sourcing or sinking
20
Specified at f = 10kHz (MAX4292/MAX4294 only)
83
dB
GBWP
500
kHz
Phase Margin
φM
65
degrees
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
mA
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
MAX4291
±3000
MAX4292/MAX4294
±2000
µA
µV
_______________________________________________________________________________________
3
MAX4291/MAX4292/MAX4294
ELECTRICAL CHARACTERISTICS (continued)
MAX4291/MAX4292/MAX4294
Ultra-Small, 1.8V, µPower,
Rail-to-Rail I/O Op Amps
ELECTRICAL CHARACTERISTICS (continued)
(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
±90
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
Tested for
MAX4291
0 ≤ VCM ≤ 1.8V,
MAX4292/MAX4294
VCC = 1.8V
50
Tested for
MAX4291
0 ≤ VCM ≤ 5.0V,
MAX4292/MAX4294
VCC = 5.0V
60
Input Bias Current
Common-Mode Rejection Ratio
Power-Supply Rejection Ratio
CMRR
PSRR
VCC = 1.8V
Large-Signal Voltage Gain
dB
53
AV
VCC = 5.0V
Output-Voltage Swing High
VOH
Specified as
|VCC - VOH|
Output-Voltage Swing Low
VOL
Specified as
|VEE - VOL|
62
dB
dB
75
dB
RL = 100kΩ,
0.02V ≤ VOUT ≤ VCC - 0.02V
80
RL = 2kΩ,
0.1V ≤ VOUT ≤ VCC - 0.1V
80
RL = 100kΩ,
0.02V ≤ VOUT ≤ VCC - 0.02V
80
RL = 2kΩ,
0.1V ≤ VOUT ≤ VCC - 0.1V
80
dB
RL = 100kΩ to VCC/2
20
RL = 2kΩ to VCC/2
40
RL = 100kΩ to VCC/2
80
RL = 2kΩ to VCC/2
Note 1: All devices are 100% tested at TA = +25°C. All temperature limits are guaranteed by design.
4
_______________________________________________________________________________________
120
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
1.7
1.6
1.5
1.4
1.3
1.2
VCC = 5.5V
-300
-450
VCC = 2.4V
-600
VCC = 1.8V
-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
10
0
-10
-20
-40
-40
-0.5
-55 -40 -25 -10 5 20 35 50 65 80 95 110 125
20
-30
-30
0
MAX4291 toc06
30
0
0.5
1.0
1.5
2.0
-0.5
2.5
0.5
1.5
2.5
3.5
4.5
5.5
TEMPERATURE (°C)
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
60
VOL (VCC = 5.5V)
20
15
10
VOH (VCC = 5.5V OR 1.8V)
VOL (VCC = 1.8V)
5
VOH = VCC - VOUT
VOL = VOUT - VEE
50
-75
40
30
VOH (VCC = 5.5V)
VOL (VCC = 1.8V)
-25
5
35
65
TEMPERATURE (°C)
95
125
VCC = 1.8V
-80
-85
VCC = 5.5V
-90
20
-95
10
-100
-105
0
-55
0 ≤ VCM ≤ VCC
-70
VOL (VCC = 5.5V)
VOH (VCC = 1.8V)
0
-65
CMRR (dB)
25
OUTPUT VOLTAGE SWING (mV)
MAX4291-07
VOH = VCC - VOUT
VOL = VOUT - VEE
MAX4291 toc09
20
40
INPUT BIAS CURRENT (nA)
25
10
30
INPUT BIAS CURRENT (nA)
30
-55 -40 -25 -10 5 20 35 50 65 80 95 110 125
MAX4291 toc05
40
MAX4291 toc04
35
OUTPUT VOLTAGE SWING (mV)
-150
-750
1.0
60
30
MAX4291 toc03
1.8
0
1.1
70
INPUT BIAS CURRENT (nA)
1.9
INPUT OFFSET VOLTAGE (µV)
130
2.0
MAX4291-08
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)
-55
-25
5
35
65
TEMPERATURE (°C)
95
125
-55 -40 -25 -10 5 20 35 50 65 80 95 110 125
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.)
Typical Operating Characteristics (continued)
(VCC = 2.4V, VEE = VCM = 0, VOUT = VCC/2, no load, TA = +25°C, unless otherwise noted.)
OPEN-LOOP GAIN vs. OUTPUT SWING HIGH
(VCC = 1.8V, RL CONNECTED TO VEE)
RL = 1kΩ
RL = 2kΩ
110
RL = 1kΩ
110
90
RL = 1kΩ
GAIN (dB)
100
90
80
70
0
50
0
50 100 150 200 250 300 350 400 450 500
50 100 150 200 250 300 350 400 450 500
VOH (mV)
VOL (mV)
OPEN-LOOP GAIN vs. OUTPUT SWING HIGH
(VCC = 5.5V, RL CONNECTED TO VEE)
OPEN-LOOP GAIN vs. TEMPERATURE
MAX4292/MAX4294
CROSSTALK vs. FREQUENCY
RL = 1kΩ TO VCC
80
60
50
50
50 100 150 200 250 300 350 400 450 500
-80
VCC = 5.5V
-90
MAX4291 toc17
144
40
108
40
108
30
72
30
72
20
36
20
36
10
0
10
0
0.1
1
10
100
FREQUENCY (kHz)
1000
AV = 1000V/V
180
0
-36
-10
-72
-108
-20
-108
-144
-30
-144
-180
-40
-20
-40
PHASE (DEGREES)
GAIN (dB)
50
-30
-180
0.1
100
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
144
-72
10
GAIN AND PHASE vs. FREQUENCY
(CL = 100pF)
50
-36
1
FREQUENCY (kHz)
60
0
0.1
TEMPERATURE (°C)
180
-10
0.01
-55 -40 -25 -10 5 20 35 50 65 80 95 110 125
GAIN AND PHASE vs. FREQUENCY
(CL = 0)
AV = 1000V/V
-50
-60
-70
VOH (mV)
60
-30
-40
1
10
100
FREQUENCY (kHz)
1000
1
1000
MAX4291 toc18
70
60
MAX4291 toc16
RL = 1kΩ TO VEE
RL = 2kΩ TO VEE
90
70
0
CROSSTALK (dB)
100
THD + NOISE (%)
80
-20
PHASE (DEGREES)
90
-10
110
RL = 2kΩ TO VCC
MAX4291-15
120
OPEN-LOOP GAIN (dB)
100
0
MAX4291 toc14
RL = 1kΩ
110
130
MAX4191 toc13
RL = 2kΩ
120
6
0
50 100 150 200 250 300 350 400 450 500
VOL (mV)
130
GAIN (dB)
60
50
50
90
70
60
60
100
80
80
70
RL = 2kΩ
120
100
GAIN (dB)
GAIN (dB)
110
130
MAX4291 toc11
RL = 2kΩ
120
120
MAX4291 toc10
130
OPEN-LOOP GAIN vs. OUTPUT SWING LOW
(VCC = 5.5V, RL CONNECTED TO VCC)
MAX4191 toc12
OPEN-LOOP GAIN vs. OUTPUT SWING LOW
(VCC = 1.8V, RL CONNECTED TO VCC)
GAIN (dB)
MAX4291/MAX4292/MAX4294
Ultra-Small, 1.8V, µPower,
Rail-to-Rail I/O Op Amps
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
100
VCC = 2.5V
VEE = -2.5V
VCM = 0
MAX4291 toc21
VCC = 2.5V
VEE = -2.5V
VCM = 0
100mV
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
10
1µs/div
1µs/div
CAPACITIVE LOAD (nF)
LARGE-SIGNAL TRANSIENT RESPONSE
(INVERTING CONFIGURATION)
LARGE-SIGNAL TRANSIENT RESPONSE
(NONINVERTING CONFIGURATION)
MAX4291 toc23
MAX4291 toc22
VCC = 2.5V
VEE = -2.5V
VCM = 0
VCC = 2.5V
VEE = -2.5V
VCM = 0
2V
2V
IN
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)
MAX4291 toc20
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
MAX4291
MAX4292
MAX4294
NAME
FUNCTION
µMAX/SO
UCSP
1
—
—
—
IN+
Noninverting Input
2
4
C2
11
VEE
Negative Supply. Connect to ground for
single-supply operation.
3
—
—
—
IN-
Inverting Input
4
—
—
—
OUT
Amplifier Output
5
8
A2
4
VCC
Positive Supply
—
1, 7
A1, A3
1, 7
OUTA, OUTB
—
2, 6
B1, B3
2, 6
INA-, INB-
—
3, 5
C1, C3
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 in the smallest
package possible. The input stage consists of separate
NPN and PNP differential stages, which operate together to provide a common-mode 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 ±200µV (MAX4292/MAX4294). 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, lowvoltage, 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
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
MAX4291/MAX4292/MAX4294
Table 1. MAX4291 Characteristics with Typical Battery Systems
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)
IN+
VCC = 2.5V, VEE = -2.5V
10.6kΩ
IN
2.5V/div
0
OUT
2.5V/div
0
IN10.6kΩ
Figure 2. Input Protection Circuit
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.
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:
(V
- 1.8V)
IBIAS = DIFF
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 unity-gain configuration, high slew-rate input signals
may capacitively couple to the output through the triplediode stacks.
20µs/div
Figure 3. Rail-to-Rail Input/Output Voltage Range
Rail-to-Rail Output Stage
The MAX4291/MAX4292/MAX4294 output stage can
drive up to a 2kΩ load and still swing to within 46mV 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 + 25mV) to (VCC - 2mV) with a 100kΩ
load.
Applications Information
Power-Supply Considerations
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 100dB
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
_______________________________________________________________________________________
9
MAX4291
OFFSET VOLTAGE vs. SUPPLY VOLTAGE
-450
30
-550
TA = +25°C
-600
TA = -40°C
-650
OUTPUT SOURCE CURRENT (mA)
-500
OFFSET VOLTAGE (µV)
OUTPUT SOURCE CURRENT
vs. TEMPERATURE
VCM = VCC/2
TA = +85°C
-700
25
20
15
10
VCC = 1.8V
VOH = 200mV
VCC = 5.5V
VOH = 100mV
VCC = 5.5V
VOH = 50mV VCC = 1.8V
VOH = 100mV VCC = 1.8V
VOH = 50mV
0
-55 -40 -25 -10 5 20 35 50 65 80 95 110 125
SUPPLY VOLTAGE (V)
TEMPERATURE (°C)
Figure 6a. Output Source Current vs. Temperature
OUTPUT SINK CURRENT
vs. TEMPERATURE
18
140
16
100
80
TA = +25°C
TA = -40°C
TA = +85°C
20
OUTPUT SINK CURRENT (mA)
120
40
VOH = VCC - VOUT
5
SUPPLY CURRENT PER AMPLIFIER
vs. SUPPLY VOLTAGE
60
VCC = 5.5V
VOH = 200mV
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
Figure 4. Offset Voltage vs. Supply Voltage
SUPPLY CURRENT (µA)
MAX4291/MAX4292/MAX4294
Ultra-Small, 1.8V, µPower,
Rail-to-Rail I/O Op Amps
VCC = 5.5V
VOL = 200mV
14
12
10
8
VCC = 5.5V
VOL = 100mV
VOL = VOUT - VEE
VCC = 5.5V
VOL = 50mV
VCC = 1.8V
VOL = 200mV
VCC = 1.8V
VOL = 100mV VCC = 1.8V
VOL = 50mV
6
4
2
0
0
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
-55 -40 -25 -10 5 20 35 50 65 80 95 110 125
SUPPLY VOLTAGE (V)
TEMPERATURE (°C)
Figure 5. Supply Current per Amplifier vs. Supply Voltage
Figure 6b. Output Sink Current vs. Temperature
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).
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.
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.
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
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
10
______________________________________________________________________________________
Ultra-Small, 1.8V, µPower,
Rail-to-Rail I/O Op Amps
IN
RISO
0
OUT
IN
MAX4291
MAX4292
MAX4294
RL
CL
100mV
OUT
0
AV =
RL
≈1
RL + RISO
Figure 7a. Using a Resistor to Isolate a Capacitive Load from
the Op Amp
100mV
IN
0
100mV
OUT
0
10µs/div
VCC = 2.4V, RL = 2kΩ TO VEE, CL = 1000pF
Figure 7b. Pulse Response Without Isolating Resistor
within 100mV of VCC and is capable of driving a 485Ω
load resistor to VEE:
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).
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
10µs/div
VCC = 2.4V, RL = 2kΩ TO VEE, CL = 1000pF, RISO = 100Ω
Figure 7c. Pulse Response with Isolating Resistor (100Ω)
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
and the VEE supplies should be bypassed to ground
with separate 100nF capacitors.
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:
______________________________________________________________________________________
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
MAX4294
VEE = GND
VOD (mV)
Figure 8. Propagation Delay vs. Input Overdrive
VHYST = VHI − VLO
R1
R1
VHI = 1 +
+
VREF
R2
RHYST
R1
VLO = VHI −
VCC
RHYST
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
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
12
VEE = GND MAX4292
70 80 90 100
Figure 9. Hysteresis Comparator Circuit
MAXIMUM SUPPLY CURRENT PER AMPLIFIER
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 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
SUPPLY VOLTAGE (V)
Figure 10. Maximum Supply Current per Amplifier vs. Supply
Voltage
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.
Calculate the output voltage of the application using
the following equation:
R1
VOUT = ILOAD × × R3
R2
______________________________________________________________________________________
Ultra-Small, 1.8V, µPower,
Rail-to-Rail I/O Op Amps
ILOAD
R1
VCC
UCSP Information
Layout Issues
Design the layout for the IC to be as compact as possible to minimize parasitics. The UCSP uses a bump
pitch of 0.5mm (19.7mil) and bump diameter of 0.3
(~12mil). Therefore, lay out the solder-pad spacing on
0.5mm (19.7mil) centers, using a pad size of 0.25mm
(~10mil) and a solder mask opening of 0.33mm (13mil).
Round or square pads are permissible. Connect multiple vias from the ground plane as close to the ground
pins as possible.
Install capacitors as close as possible to the IC supply
voltage pin. Place the ground end of these capacitors
near the IC GND pins to provide a low-impedance
return path for the signal current.
R2
Q1
VOUT
R3
MAX4291
VEE
Figure 11. Current Monitor for a 2-Cell Battery Stack
Marking Information
Prototype Chip Installation
Alignment keys on the PC board, around the area
where the chip is located, will be helpful in the prototype assembly process. It is better to align the chip on
the board before any other components are placed,
and then place the board on a hot plate or hot surface
until the solder starts melting. Remove the board from
the hot plate without disturbing the position of the chip
and let it cool down to room temperature before processing the board further.
ORIENTATION
PRODUCT ID CODE
LOT CODE
AAA
AAA
UCSP Reliability
The UCSP represents a unique packaging form factor
that may not perform as well as a packaged product
through traditional mechanical reliability tests. UCSP
reliability is integrally linked to the user’s assembly
methods, circuit board material, and usage environment. The user should closely review these areas when
considering use of a UCSP.
Performance through operating-life test and moisture
resistance remains uncompromised. The wafer-fabrication process primarily determines the performance.
Mechanical stress performance is a greater consideration for UCSPs. UCSPs are attached through direct solder contact to the user’s PC board, foregoing the
inherent stress relief of a packaged product lead frame.
Solder-joint contact integrity must be considered.
Comprehensive reliability tests have been performed
and are available upon request. In conclusion, the
UCSP performs reliably through environmental stresses.
______________________________________________________________________________________
13
MAX4291/MAX4292/MAX4294
For a 1V output and a current load of 50mA, the choice
of resistors can be R1 = 2Ω, R2 = 100kΩ, and R3 =
1MΩ.
MAX4291/MAX4292/MAX4294
Ultra-Small, 1.8V, µPower,
Rail-to-Rail I/O Op Amps
Pin Configurations (continued)
TOP VIEW
OUTA 1
INA- 2
1
8
VCC
INA- 2
7
OUTB
OUTA
IN+ 1
VEE 2
5 VCC
MAX4291
4 OUT
IN- 3
SC70/SOT23
MAX4292
14 OUTD
MAX4294
13 IND-
INA+ 3
12 IND+
VCC 4
11 VEE
INB+ 5
10 INC+
INA+
3
6
INB-
INB- 6
9 INC-
VEE
4
5
INB+
OUTB 7
8 OUTC
µMAX/SO
TSSOP/SO
Chip Information
MAX4291 TRANSISTOR COUNT: 149
MAX4292 TRANSISTOR COUNT: 356
MAX4294 TRANSISTOR COUNT: 747
PROCESS: BiCMOS
14
______________________________________________________________________________________
Ultra-Small, 1.8V, µPower,
Rail-to-Rail I/O Op Amps
SOT5L.EPS
SC70, 5L.EPS
______________________________________________________________________________________
15
MAX4291/MAX4292/MAX4294
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
Package Information (continued)
4X S
8
E
ÿ 0.50±0.1
8
INCHES
DIM
A
A1
A2
b
H
c
D
e
E
H
0.6±0.1
1
L
1
α
0.6±0.1
S
BOTTOM VIEW
D
MIN
0.002
0.030
MAX
0.043
0.006
0.037
0.014
0.010
0.007
0.005
0.120
0.116
0.0256 BSC
0.120
0.116
0.198
0.188
0.026
0.016
6∞
0∞
0.0207 BSC
8LUMAXD.EPS
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
MILLIMETERS
MAX
MIN
0.05
0.75
1.10
0.15
0.95
0.25
0.36
0.13
0.18
2.95
3.05
0.65 BSC
2.95
3.05
4.78
5.03
0.41
0.66
0∞
6∞
0.5250 BSC
TOP VIEW
A1
A2
e
FRONT VIEW
A
α
c
b
L
SIDE VIEW
PROPRIETARY INFORMATION
TITLE:
PACKAGE OUTLINE, 8L uMAX/uSOP
APPROVAL
DOCUMENT CONTROL NO.
21-0036
REV.
J
1
1
Note: The MAX4292 does not have an exposed pad.
TSSOP.EPS
MAX4291/MAX4292/MAX4294
Ultra-Small, 1.8V, µPower,
Rail-to-Rail I/O Op Amps
Note: The MAX4294 does not have an exposed pad.
16
______________________________________________________________________________________
Ultra-Small, 1.8V, µPower,
Rail-to-Rail I/O Op Amps
SOICN.EPS
______________________________________________________________________________________
17
MAX4291/MAX4292/MAX4294
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
9LUCSP, 3x3.EPS
MAX4291/MAX4292/MAX4294
Ultra-Small, 1.8V, µPower,
Rail-to-Rail I/O Op Amps
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.
18 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2002 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
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