MAX951–MAX954
General Description
The MAX951–MAX954 feature combinations of a micropower operational amplifier, comparator, and reference
in an 8-pin package. In the MAX951 and MAX952, the
comparator’s inverting input is connected to an internal
1.2V ±2% bandgap reference. The MAX953 and MAX954
are offered without an internal reference. The MAX951/
MAX952 operate from a single 2.7V to 7V supply with a
typical supply current of 7μA, while the MAX953/MAX954
operate from 2.4V to 7V with a 5μA typical supply current.
Both the op amp and comparator feature a commonmode input voltage range that extends from the negative
supply rail to within 1.6V of the positive rail, as well as
output stages that swing Rail-to-Rail®.
Ultra-Low-Power, Single-Supply
Op Amp + Comparator + Reference
Features
●● Op Amp + Comparator + Reference in an 8-Pin
μMAX Package (MAX951/MAX952)
●● 7μA Typical Supply Current (Op Amp + Comparator +
Reference)
●● Comparator and Op Amp Input Range Includes
Ground
●● Outputs Swing Rail to Rail
●● 2.4V to 7V Supply Voltage Range
●● Unity-Gain Stable and 125kHz Decompensated
AV ≥ 10V/V Op Amp Options
●● Internal 1.2V ±2% Bandgap Reference
The op amps in the MAX951/MAX953 are internally compensated to be unity-gain stable, while the op amps in the
MAX952/MAX954 feature 125kHz typical bandwidth, 66V/
ms slew rate, and stability for gains of 10V/V or greater.
These op amps have a unique output stage that enables
them to operate with an ultra-low supply current while
maintaining linearity under loaded conditions. In addition,
they have been designed to exhibit good DC characteristics over their entire operating temperature range, minimizing input-referred errors.
●● Internal Comparator Hysteresis
MAX951
Yes
1
Yes
7
The comparator output stage of these devices continuously sources as much as 40mA. The comparators eliminate power-supply glitches that commonly occur when
changing logic states, minimizing parasitic feedback and
making the devices easier to use. In addition, they contain
±3mV internal hysteresis to ensure clean output switching, even with slow-moving input signals.
MAX952
Yes
10
Yes
7
MAX953
No
1
Yes
5
MAX954
No
10
Yes
5
Applications
●●
●●
●●
●●
●●
●●
●●
Instruments, Terminals, and Bar-Code Readers
Battery-Powered Systems
Low-Frequency, Local-Area Alarms/Detectors
Photodiode Preamps
Smart Cards
Infrared Receivers for Remote Controls
Smoke Detectors and Safety Sensors
Rail-to-Rail is a registered trademark of Nippon Motorola, Ltd.
19-0431; Rev 3; 2/15
●● Op Amp Capable of Driving up to 1000pF Load
Selector Guide
INTERNAL OP AMP
SUPPLY
2%
GAIN
PART
COMPARATOR CURRENT
PRECISION STABILITY
(µA)
REFERENCE
(V/V)
Pin Configuration
TOP VIEW
AMPOUT 1
MAX951
MAX952
MAX953
MAX954
AMPIN- 2
AMPIN+ 3
VSS 4
8
7
VDD
COMPOUT
6
REF (COMPIN-)
5
COMPIN+
DIP/SO/µAX
( ) ARE FOR MAX953/MAX954
Typical Operating Circuit and Ordering Information appear
at end of data sheet end of data sheet.
MAX951–MAX954
Ultra-Low-Power, Single-Supply
Op Amp + Comparator + Reference
Absolute Maximum Ratings
Supply Voltage (VDD to VSS)...................................................9V
Inputs
Current (AMPIN_, COMPIN_).........................................20mA
Voltage (AMPIN_, COMPIN_)...(VDD + 0.3V) to (VSS - 0.3V)
Outputs
Current (AMPOUT, COMPOUT)......................................50mA
Current (REF)..................................................................20mA
Voltage (AMPOUT, COMPOUT,
REF)..........................................(VDD + 0.3V) to (VSS - 0.3V)
Short-Circuit Duration (REF, AMPOUT)..................Continuous
Short-Circuit Duration (COMPOUT, VDD to VSS ≤ 7V)...1min
Continuous Power Dissipation (TA = +70°C)
8-Pin Plastic DIP (derate 9.09mW/°C above +70°C)...727mW
8-Pin SO (derate 5.88mW/°C above +70°C)................471mW
8-Pin μMAX (derate 4.10mW/°C above +70°C)...........330mW
8-Pin CERDIP (derate 8.00mW/°C above +70°C).......640mW
Operating Temperature Ranges
MAX95_E_A ....................................................-40°C to +85°C
MAX95_MJA..................................................-55°C to +125°C
Maximum Junction Temperatures
MAX95_E_A.................................................................+150°C
MAX95_MJA.................................................................+175°C
Storage Temperature Range .............................-65°C to +165°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
(VDD = 2.8V to 7V for MAX951/MAX952, VDD = 2.4V to 7V for MAX953/MAX954, VSS = 0, VCM COMP = 0 for the MAX953/MAX954,
VCM OPAMP = 0, AMPOUT = (VDD + VSS)/2, COMPOUT = low, TA = TMIN to TMAX, typical values are at TA = +25°C, unless otherwise noted.)
PARAMETER
Supply Voltage Range
SYMBOL
VDD
CONDITIONS
MAX951/MAX952
MAX
7.0
TA = -10°C to +85°C
2.7
7.0
2.4
7.0
TA = +25°C, MAX951/MAX952
IS
TYP
2.8
MAX953/MAX954
Supply Current
(Note 1)
MIN
TA = TMIN to TMAX
7
11
MAX951M/MAX952M
13
5
V
10
MAX951E/MAX952E
TA = +25°C, MAX953/MAX954
UNITS
8
MAX953E/MAX954E
9
MAX953M/MAX954M
11
µA
COMPARATOR
TA = +25°C
Input Offset Voltage
(Note 2)
Trip Point
(Note 3)
Input Leakage Current
(Note 4)
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VOS
1
3
MAX95_EPA/ESA
14
MAX95_EUA (μMAX)
14
MAX95_MJA
6
TA = +25°C
4
MAX95_EUA (μMAX)
17
MAX95_EPA/ESA
5
MAX95_MJA
7
TA = +25°C
0.003
MAX95_E
0.003
MAX95_M
mV
mV
0.050
5
nA
40
Maxim Integrated │ 2
MAX951–MAX954
Ultra-Low-Power, Single-Supply
Op Amp + Comparator + Reference
Electrical Characteristics (continued)
(VDD = 2.8V to 7V for MAX951/MAX952, VDD = 2.4V to 7V for MAX953/MAX954, VSS = 0, VCM COMP = 0 for the MAX953/MAX954,
VCM OPAMP = 0, AMPOUT = (VDD + VSS)/2, COMPOUT = low, TA = TMIN to TMAX, typical values are at TA = +25°C, unless otherwise noted.)
PARAMETER
SYMBOL
Common-Mode Input
Range
CMVR
Common-Mode Rejection
Ratio
CMRR
Power-Supply Rejection
Ratio
PSRR
Response Time
tpd
CONDITIONS
MIN
TYP
VSS
MAX
VDD -1.6V
VSS to (VDD - 1.6V), MAX953/MAX954
0.1
1
MAX951/MAX952, VDD = 2.8V to 7V
0.05
1
MAX953/MAX954, VDD = 2.4V to 7V
0.05
1
CL = 100pF, TA = +25°C,
VDD - VSS = 5V
Output High Voltage
VOH
ISOURCE = 2mA
Output Low Voltage
VOL
ISINK = 1.8mA
VOD = 10mV
22
VOD = 100mV
4
UNITS
V
mV/V
mV/V
µs
VDD - 0.4V
V
VSS + 0.4V
V
REFERENCE
Reference Voltage
(Note 5)
VREF
MAX95_EPA/ESA
1.176
1.200
1.224
MAX95_EUA (μMAX)
1.130
1.200
1.270
MAX95_MJA
1.164
1.200
1.236
IOUT = ±20μA, TA = +25°C
Load Regulation
0.1
IOUT = ±6μA, MAX95_E
1.5
IOUT = ±3μA, MAX95_M
Voltage Noise
en
V
%
1.5
0.1Hz to 10Hz
16
TA = +25°C
1
μVP-P
OP AMP
Input Offset Voltage
Input Bias Current
VOS
IB
Large-Signal Gain
(No Load)
AVOL
Large-Signal Gain
(100kΩ Load to VSS)
AVOL
Gain Bandwidth
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GBW
3
MAX95_EPA/ESA
4
MAX95_EUA (μMAX)
5
MAX95_MJA
5
TA = +25°C
0.003
MAX95_E
0.003
5
MAX95_M
0.003
40
AMPOUT = 0.5V to
4.5V, VDD - VSS = 5V
AMPOUT = 0.5V to
4.5V, VDD - VSS = 5V
TA = +25°C
100
MAX95_E
50
MAX95_M
10
TA = +25°C
40
MAX95_E
25
MAX95_M
5
mV
0.050
nA
1000
V/mV
150
V/mV
AV = 1V/V, MAX951/MAX953, VDD - VSS = 5V
20
AV = 10V/V, MAX952/MAX954, VDD - VSS = 5V
125
kHz
Maxim Integrated │ 3
MAX951–MAX954
Ultra-Low-Power, Single-Supply
Op Amp + Comparator + Reference
Electrical Characteristics (continued)
(VDD = 2.8V to 7V for MAX951/MAX952, VDD = 2.4V to 7V for MAX953/MAX954, VSS = 0, VCM COMP = 0 for the MAX953/MAX954,
VCM OPAMP = 0, AMPOUT = (VDD + VSS)/2, COMPOUT = low, TA = TMIN to TMAX, typical values are at TA = +25°C, unless otherwise noted.)
PARAMETER
Slew Rate
SYMBOL
SR
Common-Mode Input
Range
CMVR
Common-Mode Rejection
Ratio
CMRR
Power-Supply Rejection
Ratio
PSRR
CONDITIONS
12.5
AV = 10V/V, MAX952/MAX954, VDD - VSS = 5V
66
VSS
VDD = 2.8V to 7V, MAX951/MAX952
0.07
1.0
VDD = 2.4V to 7V, MAX953/MAX954
0.07
1.0
VOH
RL = 100kΩ to VSS
Output Low Voltage
VOL
RL = 100kΩ to VSS
ISNK
VDD - 1.6
1
fo = 1kHz
fo = 0.1Hz to 10Hz
TA = +25°C, VDD - VSS = 5V
300
MAX95_E
60
MAX95_M
40
TA = +25°C
70
TA = +25°C, VDD - VSS = 5V
200
MAX95_E
50
MAX95_M
30
mV/V
mV/V
nV√Hz
1.2
μVP-P
V
VSS + 50mV
70
V
80
VDD - 500mV
TA = +25°C
UNITS
V/ms
0.03
Output High Voltage
Output Sink Current
MAX
VCM OPAMP = VSS to (VDD - 1.6V)
en
ISRC
TYP
AV = 1V/V, MAX951/MAX953, VDD - VSS = 5V
Input Noise Voltage
Output Source Current
MIN
820
570
V
µA
µA
Note 1: Supply current is tested with COMPIN+ = (REF - 100mV) for MAX951/MAX952, and COMPIN+ = 0 for MAX953/MAX954.
Note 2: Input Offset Voltage is defined as the center of the input-referred hysteresis. VCM COMP = REF for MAX951/MAX952, and
VCM COMP = 0 for MAX953/MAX954.
Note 3: Trip Point is defined as the differential input voltage required to make the comparator output change. The difference
between upper and lower trip points is equal to the width of the input-referred hysteresis. VCM COMP = REF for MAX951/
MAX952, and VCM COMP = 0 for MAX953/MAX954.
Note 4: For MAX951/MAX952, input leakage current is measured for COMPIN- at the reference voltage. For MAX953/MAX954,
input leakage current is measured for both COMPIN+ and COMPIN- at VSS.
Note 5: Reference voltage is measured with respect to VSS. Contact factory for availability of a 3% accurate reference voltage in
the μMAX package.
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Maxim Integrated │ 4
MAX951–MAX954
Ultra-Low-Power, Single-Supply
Op Amp + Comparator + Reference
Typical Operating Characteristics
(TA = +25°C, unless otherwise noted.)
5
MAX953/MAX954
4
VCM OPAMP = 0
AMPOUT = (VDD + VSS)/2
COMP- = 1.2V or REF
COMP+ = 1.1V
VDD = 2.8V (MAX951/952), VDD = 2.4V
(MAX953/954), VSS = 0, VCM OPAMP = 0
AMPOUT = 1/2 VDD, COMP- = 1.2V or REF
COMP+ = 1.1V
2
1
0
-60 -40 -20 0
1.180
20 40 60 80 100 120 140
MAX951-954-toc03
-60 -40 -20 0
20 40 60 80 100 120 140
DC OPEN-LOOP GAIN
vs. SUPPLY VOLTAGE
60
PSRR (dB)
1.18
50
40
C
30
B
20
SOURCING CURRENT
1.14
A
A: MAX951/952 REF
B: MAX951/953 OP AMP
C: MAX952/954 OP AMP
10
1
10
0
100
1
10
LOAD CURRENT (µA)
MAX951-954-toc07
1x103
1x102
VDD = 5V
1MHz INPUT SIGNAL
RL = 100kΩ
0
20 40 60 80 100 120 140
TEMPERATURE (°C)
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1x105
1x104
1x103
1x102
1x101
10k
100k
1x100
1M
1mHz INPUT SIGNAL
RL = 100kΩ
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0
SUPPLY VOLTAGE (V)
MAX951/MAX953
OPEN-LOOP GAIN AND PHASE
vs. FREQUENCY
MAX951-954-toc08
100
80
OPEN-LOOP GAIN (dB)
1x104
-60 -40 -20
1k
1x106
FREQUENCY (Hz)
DC OPEN-LOOP GAIN
vs. TEMPERATURE
1x105
100
1x107
MAX951-954-toc06
70
SINKING CURRENT
1.16
VDD = 2.0 to 3.0V, VSS = -2.5V
NONINVERTING
AMPIN+ = 0
ACL = 1V/V (MAX951/2)
ACL = 10V/V (MAX953/4),
COMP- = 1.2V or REF
COMP+ = 1.1V from VSS
DC OPEN-LOOP GAIN (V/V)
80
1.12
DC OPEN-LOOP GAIN (V/V)
VDD = 5V
1.185
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
1.20
1x100
1.190
REFERENCE OUTPUT VOLTAGE
vs. LOAD CURRENT
1.22
1x101
1.195
TEMPERATURE (°C)
1.24
1x106
1.200
TEMPERATURE (°C)
1.26
1.10
MAX951-954-toc02
3
1.205
SUPPLY VOLTAGE (V)
VSUPPLY = 5V
1.28
MAX953/MAX954
4
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0
1.30
REFERENCE VOLTAGE (V)
5
1.210
PHASE
60
100
-60
80
-120
GAIN
40
0
-180
20
-240
0
-300
RL = 100kΩ
-20
1
10
100
1k
10k
FREQUENCY (Hz)
100k
-360
1M
OPEN-LOOP GAIN (dB)
1
6
1.215
PHASE SHIFT (Degrees)
2
MAX951/MAX952
MAX951-954-toc05
3
7
1.220
MAX952/MAX954
OPEN-LOOP GAIN AND PHASE
vs. FREQUENCY
MAX951-954-toc09
0
-60
60
PHASE
40
-120
-180
GAIN
-240
20
0
-300
RL = 100kΩ
-20
1
10
100
1k
10k
100k
1M
-360
FREQUENCY (Hz)
Maxim Integrated │ 5
PHASE SHIFT (Degrees)
MAX951/MAX952
6
8
SUPPLY CURRENT (µA)
7
REFERENCE VOLTAGE vs. TEMPERATURE
9
MAX951-954-toc04
SUPPLY CURRENT (µA)
8
0
10
MAX951-954-toc01
9
SUPPLY CURRENT
vs. TEMPERATURE
REFERENCE VOLTAGE (V)
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX951–MAX954
Ultra-Low-Power, Single-Supply
Op Amp + Comparator + Reference
Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
0.04
SINKING CURRENT
0.02
0.10
-0.02
SOURCING CURRENT
-0.04
-0.06
F
1
10
100
NONINVERTING
AMPIN+ = (VDD - VSS)/2
1500
1000
SHORT TO VSS
500
0
SHORT TO VDD
-500
NONINVERTING
AMPIN+ = GND
-0.08
-0.10
E
D
1000
-1000
2000
2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0
SUPPLY VOLTAGE (V)
LOAD CURRENT (µA)
OVERSHOOT (%)
80
70
60
50
40
PARTS–VSUPPLY
A: MAX951/952, 3V
B: MAX951/953, 5V
D: MAX952/954, 3V
E: MAX952/954, 5V
MAX951/953, A = 1V/V
MAX952/954, A = 10V/V
AMPOUT = 1VP-P
VCM = (VDD - VSS/2)
30
COMPARATOR OUTPUT VOLTAGE
vs. LOAD CURRENT
5.0
C
E
D
4.5
OUTPUT VOLTAGE (V)
90
OP AMP PERCENT OVERSHOOT
vs. CAPACITIVE LOAD
MAX951–954 TOC12
100
B
A
SOURCING CURRENT
4.0
3.5
3.0
2.5
2.0
1.5
VSUPPLY = 5V
20
1.0
10
0.5
SINKING CURRENT
0
0.01
0.1
1
0
101
102
MAX951–954 TOC11
C
B
103
104
105
CAPACITIVE LOAD (pF)
106
MAX951–954 TOC13
0.06
A
2000
OUTPUT CURRENT (µA)
A, D: VSUPPLY = ±1.5V
B, E: VSUPPLY = ±2.5V
C, F: VSUPPLY = ±3.5V
0.08
MAX951–954 TOC10
0.10
OUTPUT VOLTAGE (V)
OP AMP SHORT-CIRCUIT CURRENT
vs. SUPPLY VOLTAGE
OP AMP OUTPUT VOLTAGE
vs. LOAD CURRENT
10
100 200
LOAD CURRENT (mA)
COMPARATOR SHORT-CIRCUIT
CURRENT vs. SUPPLY VOLTAGE
MAX951-954 TOC14
SHORT-CIRCUIT CURRENT (mA)
250
200
150
SOURCING CURRENT
100
50
0
-50
SINKING CURRENT
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0
SUPPLY VOLTAGE (V)
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Maxim Integrated │ 6
MAX951–MAX954
Ultra-Low-Power, Single-Supply
Op Amp + Comparator + Reference
Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
OUTPUT
1V/div
COMPARATOR RESPONSE TIME
FOR VARIOUS INPUT OVERDRIVES (RISING)
MAX951-954 TOC16
MAX951-954 TOC15
COMPARATOR RESPONSE TIME
FOR VARIOUS INPUT OVERDRIVES (FALLING)
INPUT
100mV/div
0
100mV
20mV 10mV
50mV
0
INPUT
100mV/div
OUTPUT
1V/div
100mV
10mV
20mV
50mV
0
0
2µs/div
2µs/div
MAX953: LOAD = 100kΩ || 100pF, VSUPPLY = 5V
MAX953: LOAD = 100kΩ || 100pF, VSUPPLY = 5V
MAX951-954 TOC17
OUTPUT
50mV/div
INPUT
2V/div
2.5V
OUTPUT
1V/div
100µs/div
NONINVERTING: AVCL = 1V/V,
LOAD = 100kΩ || 100pF to VSS, VSUPPLY = 5V
200µs/div
NONINVERTING, AVCL = 1V/V,
LOAD = 100kΩ || 100pF to VSS, VSUPPLY = 5V
MAX952/MAX954 OP AMP
SMALL-SIGNAL TRANSIENT RESPONSE
MAX952/MAX954 OP AMP
LARGE-SIGNAL TRANSIENT RESPONSE
MAX951-954 TOC19
INPUT
20mV/div
OUTPUT
50mV/div
2.5V
100µs/div
NONINVERTING, AVCL = 10V/V,
LOAD = 100kΩ || 100pF to VSS, VSUPPLY = 5V
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2.5V
MAX951-954 TOC20
INPUT
200mV/div
MAX951-954 TOC18
MAX951/MAX953 OP AMP
LARGE-SIGNAL TRANSIENT RESPONSE
MAX951/MAX953 OP AMP
SMALL-SIGNAL TRANSIENT RESPONSE
INPUT
200mV/div
OUTPUT
1V/div
2.5V
100µs/div
NONINVERTING, AVCL = 10V/V,
LOAD = 100kΩ || 100pF to VSS, VSUPPLY = 5V
Maxim Integrated │ 7
MAX951–MAX954
Ultra-Low-Power, Single-Supply
Op Amp + Comparator + Reference
Pin Description
PIN
MAX951
MAX952
MAX953
MAX954
NAME
1
1
AMPOUT
2
2
AMPIN-
Inverting Op Amp Input
3
3
AMPIN+
Noninverting Op Amp Input
4
4
VSS
Negative Supply or Ground
5
5
COMPIN+
6
—
REF
—
6
COMPIN-
7
7
COMPOUT
8
8
VDD
FUNCTION
Op Amp Output
Noninverting Comparator Input
1.200V Reference Output. Also connected to inverting comparator input.
Inverting Comparator Input
Comparator Output
Positive Supply
Functional Diagrams
AMPOUT
1
OP AMP
2
AMPIN-
3
AMPIN+
4
VSS
VDD
8
COMPOUT
7
x1
1.20V
MAX951
MAX952
COMP
REF
6
COMPIN+
5
AMPOUT
1
OP AMP
2
AMPIN-
3
AMPIN+
4
MAX953
MAX954
COMP
VSS
VDD
8
COMPOUT
7
COMPIN-
6
COMPIN+
5
Figure 1. MAX951–MAX954 Functional Diagrams
Detailed Description
inputs and a common-mode input voltage range that
extends from the negative supply rail to within 1.6V of the
positive rail. They have a CMOS output stage that swings
rail to rail and is driven by a proprietary high gain stage,
which enables them to operate with an ultra-low supply
current while maintaining linearity under loaded conditions. Careful design results in good DC characteristics
over their entire operating temperature range, minimizing
input referred errors.
Op Amp
Comparator
The MAX951–MAX954 are combinations of a micropower
op amp, comparator, and reference in an 8-pin package, as shown in Figure 1. In the MAX951/MAX952, the
comparator’s negative input is connected to a 1.20V ±2%
bandgap reference. All four devices are optimized to operate from a single supply. Supply current is less than 10μA
(7μA typical) for the MAX951/MAX952 and less than 8μA
(5μA typical) for the MAX953/MAX954.
The op amps in the MAX951/MAX953 are internally compensated to be unity-gain stable, while the op amps in the
MAX952/MAX954 feature 125kHz typical gain bandwidth,
66V/ms slew rate, and stability for gains of 10V/V or greater. All these op amps feature high-impedance differential
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The comparator in the MAX951–MAX954 has a highimpedance differential input stage with a common-mode
input voltage range that extends from the negative supply
rail to within 1.6V of the positive rail. Their CMOS output
stage swings rail-to-rail and can continuously source as
much as 40mA. The comparators eliminate power-supply
Maxim Integrated │ 8
MAX951–MAX954
Ultra-Low-Power, Single-Supply
Op Amp + Comparator + Reference
R2
R2
RA
R1
VIN
COMPOUT
REF
VS
COMPOUT
RB
REF
Figure 2. External Hysteresis
glitches that commonly occur when changing logic states,
minimizing parasitic feedback and making them easier to
use. In addition, they include internal hysteresis (±3mV)
to ensure clean output switching, even with slow-moving
input signals. The inputs can be taken above and below
the supply rails up to 300mV without damage. Input
voltages beyond this range can forward bias the ESDprotection diodes and should be avoided.
The MAX951–MAX954 comparator outputs swing rail-torail (from VDD to VSS). TTL compatibility is assured by
using a 5V ±10% supply.
The MAX951–MAX954 comparators continuously output
source currents as high as 40mA and sink currents of
over 5mA, while keeping quiescent currents in the microampere range. The output can source 100mA (at VDD =
5V) for short pulses, as long as the package’s maximum
power dissipation is not exceeded. The output stage does
not generate crowbar switching currents during transitions; this minimizes feedback through the supplies and
helps ensure stability without bypassing.
Reference
The internal reference in the MAX951/MAX952 has an
output of 1.20V with respect to VSS. Its accuracy is ±2%
in the -40°C to +85°C temperature range. It is comprised
of a trimmed bandgap reference fed by a proportional-toabsolute-temperature (PTAT) current source and buffered
by a micropower unity-gain amplifier. The REF output is
typically capable of sourcing and sinking 20μA. Do not
bypass the reference output. The reference is stable for
capacitive loads less than 100pF.
Applications Information
The micropower MAX951–MAX954 are designed to
extend battery life in portable instruments and add functionality in power-limited industrial controls. Following are
some practical considerations for circuit design and layout.
www.maximintegrated.com
Comparator Hysteresis
Hysteresis increases the comparator’s noise immunity by
increasing the upper threshold and decreasing the lower
threshold. The comparator in these devices contain a
±3mV wide internal hysteresis band to ensure clean output switching, even with slow-moving signals.
When necessary, hysteresis can be increased by using
external resistors to add positive feedback, as shown in
Figure 2. This circuit increases hysteresis at the expense
of more supply current and a slower response. The
design procedure is as follows:
1) Set R2. The leakage current in COMPIN+ is less than
5nA (up to +85°C), so current through R2 can be as
little as 500nA and still maintain good accuracy. If R2
= 2.4MΩ, the current through R2 at the upper trip point
is VREF/R2 or 500nA.
2) Choose the width of the hysteresis band. In this example choose VEHYST = 50mV
− 2VIHYST
V
R1 = R2 EHYST
(VDD + 2VIHYST )
where the internal hysteresis is VIHYST = 3mV.
3) Determine R1. If the supply voltage is 5V, then R1 =
24kΩ.
4) Check the hysteresis trip points. The upper trip point is
VIN(H) =
(R1 + R2)
R2
(VREF + VIHYST )
or 1.22V in our example. The lower trip point is 50mV
less, or 1.17V in our example.
If a resistor divider is used for R1, the calculations
should be modified using a Thevenin equivalent
model.
5) Determine RA:
Maxim Integrated │ 9
MAX951–MAX954
Ultra-Low-Power, Single-Supply
Op Amp + Comparator + Reference
VCC = 5V
ANTENNA
AMPIN+
0.1µF
AMPOUT
R2
L1
330mH
C1A
390pF
2pF to 10pF
Figure 3. Compensation for Feedback-Node Capacitance
V
R A ≈ R2 SHYST , for VSHYST >> VIHYST
VDD
In the example, RA is again 24kΩ.
6) Select the upper trip point VS(H). Our example is set at
4.75V.
7) Calculate RB.
RB =
(
(VREF
(R2) VS(H)
+ VIHYST ) (R2)(R A )
) − (VREF + VIHSYT )(R A + R2)
where RB is 8.19kΩ, or approximately 8.2kΩ.
Input Noise Considerations
Because low power requirements often demand highimpedance circuits, effects from radiated noise are more
significant. Thus, traces between the op amp or comparator inputs and any resistor networks attached should be
kept as short as possible.
Crosstalk
Reference
Internal crosstalk to the reference from the comparator is
package dependent. Typical values (VDD = 5V) are 45mV
for the plastic DIP package and 32mV for the SO package. Applications using the reference for the op amp or
external circuitry can eliminate this crosstalk by using a
simple RC lowpass filter, as shown in Figure 5.
Op Amp
Internal crosstalk to the op amp from the comparator is
package dependent, but not input-referred. Typical values (VDD = 5V) are 4mV for the plastic DIP package and
280μV for the SO package.
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0.1µF
20kΩ
10MΩ
AMP
C1B
330pF
R1
L1 x C1 =
MAX952
1
(2�fC)2
C1C
20pF to
60pF
1MΩ
100kΩ 1.2V COMP
5.1MΩ
REF
LAYOUT-SENSITIVE AREA,
METAL RFI SHIELDING ADVISED
Figure 4. Low-Frequency Radio Receiver Application
Op Amp Stability and Board Layout
Considerations
Unlike other industry-standard micropower CMOS op
amps, the op amps in the MAX951–MAX954 maintain
stability in their minimum gain configuration while driving
heavy capacitive loads, as demonstrated in the MAX951/
MAX953 Op Amp Percent Overshoot vs. Capacitive Load
graph in the Typical Operating Characteristics.
Although this family is primarily designed for low-frequency applications, good layout is extremely important. Lowpower, high-impedance circuits may increase the effects
of board leakage and stray capacitance. For example, the
combination of a 10MΩ resistance (from leakage between
traces on a contaminated, poorly designed PC board) and
a 1pF stray capacitance provides a pole at approximately
16kHz, which is near the amplifier’s bandwidth. Board
routing and layout should minimize leakage and stray
capacitance. In some cases, stray capacitance may be
unavoidable and it may be necessary to add a 2pF to 10pF
capacitor across the feedback resistor to compensate;
select the smallest capacitor value that ensures stability.
Input Overdrive
With 100mV overdrive, comparator propagation delay is
typically 6μs. The Typical Operating Characteristics show
propagation delay for various overdrive levels.
Supply current can increase when the op amp in the
MAX951–MAX954 is overdriven to the negative supply
rail. For example, when connecting the op amp as a comparator and applying a -100mV input overdrive, supply
current rises by around 15μA and 32μA for supply voltages of 2.8V and 7V, respectively.
Maxim Integrated │ 10
MAX951–MAX954
51Ω
VCC = 5V
C2
15pF, 5%
10kHz
5VP-P
NEC
SE307-C
Ultra-Low-Power, Single-Supply
Op Amp + Comparator + Reference
MAX953
VCC
NEC
PH302B
R2
1.0MΩ,1%
R1A
C1
49.9kΩ, 1% 150pF, 5%
R1B
49.9kΩ, 1%
MAX952
0.1µF
30kΩ
AMP
100kΩ
COMP
1.2V
0.1µF
LAYOUT-SENSITIVE AREA
1
R1 x C1 = R2 x C2 =
10MΩ
REF
4.7MΩ
RADIOACTIVE
IONIZATION
CHAMBER
SMOKE SENSOR
AMP
COMP
LAYOUT-SENSITIVE AREA
5.1MΩ
2� fC
Figure 5. Infrared Receiver Application
Figure 6. Sensor Preamp and Alarm Trigger Application
Power-Supply Bypassing
bandpass filter to reduce disturbances from noise and
eliminate low-frequency interference from sunlight, fluorescent lights, etc. This circuit is applicable for TV remote
controls and low-frequency data links up to 20kbps.
Carrier frequencies are limited to around 10kHz. 10kHz is
used in the example circuit.
Power-supply bypass capacitors are not required if the
supply impedance is low. For single-supply applications,
it is good general practice to bypass VDD with a 0.1μF
capacitor to ground. Do not bypass the reference output.
Applications Circuits
Low-Frequency Radio Receiver for
Alarms and Detectors
The circuit in Figure 4 is useful as a front end for low-frequency RF alarms. The unshielded inductor (M7334-ND
from Digikey) is used with capacitors C1A, C1B, and C1C
in a resonant circuit to provide frequency selectivity. The
op amp from a MAX952 amplifies the signal received. The
comparator improves noise immunity, provides a signal
strength threshold, and translates the received signal into
a pulse train. Carrier frequencies are limited to around
10kHz. 10kHz is used in the example in Figure 4.
The layout and routing of components for the amplifier
should be tight to minimize 60Hz interference and crosstalk from the comparator. Metal shielding is recommended
to prevent RFI from the comparator or digital circuitry from
exciting the receiving antenna. The transmitting antenna
can be long parallel wires spaced about 7.2cm apart,
with equal but opposite currents. Radio waves from this
antenna will be detectable when the receiver is brought
within close proximity, but cancel out at greater distances.
Infrared Receiver Front End for
Remote Controls and Data Links
The circuit in Figure 5 uses the MAX952 as a pin photodiode preamplifier and discriminator for an infrared
receiver. The op amp is configured as a Delyiannis-Friend
www.maximintegrated.com
Component layout and routing for the amplifier should
be tight to reduce stray capacitance, 60Hz interference,
and RFI from the comparator. Crosstalk from comparator
edges will distort the amplifier signal. In order to minimize
the effect, a lowpass RC filter is added to the connection
from the reference to the noninverting input of the op amp.
Sensor Preamp and Alarm Trigger for
Smoke Detectors
The high-impedance CMOS inputs of the MAX951–
MAX954 op amps are ideal for buffering high-impedance
sensors, such as smoke detector ionization chambers,
piezoelectric transducers, gas detectors, and pH sensors. Input bias currents are typically less than 3pA at
room temperature. A 5μA typical quiescent current for the
MAX953 will minimize battery drain without resorting to
complex sleep schemes, allowing continuous monitoring
and immediate detection.
Ionization-type smoke detectors use a radioactive source,
such as Americium, to ionize smoke particles. A positive voltage on a plate attached to the source repels the
positive smoke ions and accelerates them toward an outer
electrode connected to ground. Some ions collect on an
intermediate plate. With careful design, the voltage on this
plate will stabilize at a little less than one-half the supply
voltage under normal conditions, but rise higher when
smoke increases the ion current. This voltage is buffered
Maxim Integrated │ 11
MAX951–MAX954
Ultra-Low-Power, Single-Supply
Op Amp + Comparator + Reference
by the high-input-impedance op amp of a MAX951 (Figure
6). The comparator and resistor voltage divider set an
alarm threshold to indicate a fire.
Design and fabrication of the connection from the intermediate plate of the ionization chamber to the noninverting
input of the op amp is critical, since the impedance of this
node must be well above 50MΩ. This connection must be
as short and direct as possible to prevent charge leakage
and 60Hz interference. Where possible, the grounded
outer electrode or chassis of the ionization chamber
should shield this connection to reduce 60Hz interference. Pay special attention to board cleaning, to prevent
leakage due to ionic compounds such as chlorides, flux,
and other contaminants from the manufacturing process.
Where applicable, a coating of high-purity wax may be
used to insulate this connection and prevent leakage due
to surface moisture or an accumulation of dirt.
TEMP RANGE
PIN-PACKAGE
MAX951C/D
0°C to +70°C
MAX951EPA
-40°C to +85°C
8 Plastic Dip
MAX951ESA
-40°C to +85°C
8 SO
MAX951EUA
-40°C to +85°C
8 µMAX
MAX951MJA
-55°C to +125°C
8 CERDIP**
Dice*
MAX952C/D
0°C to +70°C
MAX952EPA
-40°C to +85°C
8 Plastic Dip
MAX952ESA
-40°C to +85°C
8 SO
MAX952EUA
-40°C to +85°C
8 µMAX
MAX952MJA
-55°C to +125°C
8 CERDIP**
MAX953C/D
0°C to +70°C
MAX953EPA
-40°C to +85°C
8 Plastic Dip
MAX953ESA
-40°C to +85°C
8 SO
MAX953EUA
-40°C to +85°C
8 µMAX
MAX953MJA
-55°C to +125°C
8 CERDIP**
MAX954C/D
0°C to +70°C
MAX954EPA
-40°C to +85°C
8 Plastic Dip
MAX954ESA
-40°C to +85°C
8 SO
MAX954EUA
-40°C to +85°C
8 µMAX
Dice*
COMPOUT
AMPIN-
0.084"
(2.134mm)
AMPIN+
REF(COMPIN-)
COMPIN+
VSS
0.058"
(1.473mm)
( ) ARE FOR MAX953/MAX954
TRANSISTOR COUNT: 163
SUBSTRATE CONNECTED TO VDD
Typical Operating Circuit
0.1µF
INPUT
8
3
MAX951
MAX952
2
1
1MΩ
5
COMPOUT
R2
R1
7
6
REF 1.20V
4
Dice*
**Contact factory for availability and processing to MIL-STD-883.
VCC
AMPIN+
Dice*
MAX954MJA
-55°C to +125°C
8 CERDIP**
*Dice are tested at TA = +25°C, DC parameters only.
www.maximintegrated.com
VDD
AMPOUT
Chip Information
Ordering Information
PART
Chip Topography
VSS
Package Information
For the latest package outline information and land patterns
(footprints), go to www.maximintegrated.com/packages. Note
that a “+”, “#”, or “-” in the package code indicates RoHS status
only. Package drawings may show a different suffix character, but
the drawing pertains to the package regardless of RoHS status.
Maxim Integrated │ 12
MAX951–MAX954
Ultra-Low-Power, Single-Supply
Op Amp + Comparator + Reference
Revision History
REVISION
NUMBER
REVISION
DATE
3
2/15
DESCRIPTION
Removed automotive reference in the Applications section
PAGES
CHANGED
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits)
shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
© 2015 Maxim Integrated Products, Inc. │ 13
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