Maxim MAX953MJA, MAX954C-D, MAX954EPA, MAX954ESA, MAX954EUA Datasheet

_______________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 common-mode 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.

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.

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.

____________________________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

A

V

≥ 10V/V Op-Amp Options

♦ Internal 1.2V ±2% Bandgap Reference
♦ Internal Comparator Hysteresis
♦ Op Amp Capable of Driving up to 1000pF Load

________________________Applications

Instruments, Terminals, and Bar-Code Readers
Battery-Powered Systems
Automotive Keyless Entry
Low-Frequency, Local-Area Alarms/Detectors
Photodiode Preamps
Smart Cards
Infrared Receivers for Remote Controls
Smoke Detectors and Safety Sensors

MAX951–MAX954

Ultra-Low-Power, Single-Supply

Op Amp + Comparator + Reference

________________________________________________________________

Maxim Integrated Products

1

TOP VIEW

( ) ARE FOR MAX953/MAX954

1
2
3
4

8
7
6
5

V

DD

COMPOUT
REF (COMPIN-)
COMPIN+

V

SS

AMPIN+

AMPIN-

AMPOUT

MAX951
MAX952
MAX953
MAX954

DIP/SO/µMAX

__________________Pin Configuration

19-0431; Rev 1; 7/97

Typical Operating Circuit and Ordering Information
appear at end of data sheet.

PART

INTERNAL

2%

PRECISION

REFERENCE

OP-AMP

GAIN

STABILITY

(V/V)

COMPARATOR

SUPPLY

CURRENT

(µA)

MAX951

Yes 1 Yes 7

MAX952

Yes 10 Yes 7

MAX953

No 1 Yes 5

MAX954

No 10 Yes 5

____________________Selection Table

For free samples & the latest literature: http://www.maxim-ic.com, or phone [phone].
For small orders, phone [phone] ext. 3468.

TA= -10°C to +85°C

MAX951–MAX954

Ultra-Low-Power, Single-Supply
Op Amp + Comparator + Reference

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VDD= 2.8V to 7V for MAX951/MAX952, VDD= 2.4V to 7V for MAX953/MAX954, VSS= 0V, V

CM COMP

= 0V for the MAX953/MAX954,

V

CM OPAMP

= 0V, AMPOUT = (VDD+ VSS) / 2, COMPOUT = low, TA= T

MIN

to T

MAX

, typical values are at TA= +25°C, unless

otherwise noted.)

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.

Supply Voltage (VDDto VSS)....................................................9V

Inputs

Current (AMPIN_, COMPIN_)..........................................20mA

Voltage (AMPIN_, COMPIN_).......(V

DD

+ 0.3V) to (VSS- 0.3V)

Outputs

Current (AMPOUT, COMPOUT)......................................50mA

Current (REF)..................................................................20mA

Voltage (AMPOUT,

COMPOUT, REF)..............(V

DD

+ 0.3V) to (VSS- 0.3V)

Short-Circuit Duration (REF, AMPOUT)..................Continuous

Short-Circuit Duration (COMPOUT, V

DD

to VSS≤ 7V)......1min

Continuous Power Dissipation (T

A

= +70°C)

Plastic DIP (derate 9.09mW/°C above +70°C) ............727mW

SO (derate 5.88mW/°C above +70°C).........................471mW

µMAX (derate 4.10mW/°C above +70°C) ....................330mW

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, 10sec).............................+300°C

V

SS

to (VDD- 1.6V), MAX953/MAX954

MAX95_M

TA= +25°C, MAX951/MAX952

MAX95_E

TA= +25°C

MAX95_MJA

MAX95_EPA/ESA

MAX95_EUA (µMAX)

TA= +25°C

MAX953M/MAX954M

MAX95_MJA

MAX95_EUA (µMAX)

MAX953E/MAX954E

MAX951E/MAX952E
MAX951M/MAX952M

MAX95_EPA/ESA

TA= +25°C, MAX953/MAX954

TA= +25°C

CONDITIONS

mV/V0.1 1CMRRCommon-Mode Rejection Ratio

VV

SS

VDD-1.6VCMVRCommon-Mode Range

nA

40

Input Leakage Current
(Note 4)

0.003 5

0.003 0.050

mV

7

Trip Point
(Note 3)

5

17

4

mV

6

V

OS

Input Offset Voltage
(Note 2)

14

4

1 3

7 10

11

9

11
13

5 8

UNITSMIN TYP MAXSYMBOLPARAMETER

I

S

Supply Current
(Note 1)

µA

MAX951/MAX952
MAX953/MAX954 2.4 7.0

V2.7 7.0V

DD

2.8 7.0

Supply Voltage Range

COMPARATOR

TA= -10°C to +85°C

TA= T

MIN

to T

MAX

MAX951–MAX954

Ultra-Low-Power, Single-Supply

Op Amp + Comparator + Reference

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(VDD= 2.8V to 7V for MAX951/MAX952, VDD= 2.4V to 7V for MAX953/MAX954, VSS= 0V, V

CM COMP

= 0V for the MAX953/MAX954,

V

CM OPAMP

= 0V, AMPOUT = (VDD+ VSS) / 2, COMPOUT = low, TA= T

MIN

to T

MAX

, typical values are at TA= +25°C, unless

otherwise noted.)

MAX95_M

MAX95_E

TA= +25°C

MAX953/MAX954, VDD= 2.4V to 7V

MAX95_MJA

MAX951/MAX952, VDD= 2.8V to 7V

MAX95_EUA (µMAX)

MAX95_EPA/ESA

TA= +25°C

I

OUT

= ±20µA, TA= +25°C

MAX95_MJA

0.1Hz to 10Hz

MAX95_EUA (µMAX)

MAX95_EPA/ESA

CL= 100pF, TA=
+25°C, VDD- VSS= 5V

I

SOURCE

= 2mA

I

SINK

= 1.8mA

I

OUT

= ±3µA, MAX95_M

I

OUT

= ±6µA, MAX95_E

CONDITIONS

100 1000

nA

0.003 40

I

B

Input Bias Current 0.003 5

0.003 0.050

mV

5

V

OS

Input Offset Voltage

5

4

1 3

µVp-p16e

n

Voltage Noise

%

1.5

Load Regulation 1.5

22

mV/V

0.05 1

PSRR

0.05 1

Power-Supply Rejection Ratio

0.1

V

1.164 1.200 1.236

V

REF

Reference Voltage
(Note 5)

1.130 1.200 1.270

1.176 1.200 1.224

µs

4

T

pd

Response Time

VVDD- 0.4VV

OH

Output High Voltage

VVSS+ 0.4VV

OL

Output Low Voltage

UNITSMIN TYP MAXSYMBOLPARAMETER

50
10
40 150
25

5

AV= +1V/V, MAX951/MAX953, VDD- VSS= 5V 20

Gain Bandwidth GBW

AV= +10V/V, MAX952/MAX954, VDD- VSS= 5V 125

kHz

AV= +1V/V, MAX951/MAX953, VDD- VSS= 5V 12.5

Slew Rate SR

AV= +10V/V, MAX952/MAX954, VDD- VSS= 5V 66

V/ms

0.07 1.0

Power-Supply Rejection Ratio PSRR

VDD= 2.4V to 7V, MAX953/MAX954 0.07 1.0

mV/V

en

fo= 1kHz 80 nV√Hz

VOD= 10mV
VOD= 100mV

TA= +25°C
MAX95_E
MAX95_M
TA= +25°C
MAX95_E
MAX95_M

VDD= 2.8V to 7V, MAX951/MAX952

Input Noise Voltage

fo= 0.1Hz to 10Hz 1.2 µVp-p

AMPOUT = 0.5V to

4.5V, VDD- VSS= 5V

A

VOL

Large-Signal Gain
(no load)

V/mV

AMPOUT = 0.5V to

4.5V, VDD- VSS= 5V

A

VOL

Large-Signal Gain
(100kΩ load to VSS)

V/mV

Common-Mode Input Range CMVR V

SS

VDD- 1.6 V

Common-Mode Rejection Ratio CMRR V

CM OPAMP

= VSSto (VDD- 1.6V) 0.03 1 mV/V

REFERENCE

OP AMP

µA

MAX951–MAX954

Ultra-Low-Power, Single-Supply
Op Amp + Comparator + Reference

4 _______________________________________________________________________________________

RL= 100kΩ to V

SS

RL= 100kΩ to V

SS

TA= +25°C, VDD- VSS= 5V

TA= +25°C

MAX95_M

TA= +25°C
TA= +25°C, VDD- VSS= 5V

MAX95_M

MAX95_E

MAX95_E

CONDITIONS

30

50

VVSS+ 50mVV

OL

Output Low Voltage

VVDD- 500mVV

OH

Output High Voltage

200 570

70

40

70

300 820

60

UNITSMIN TYP MAXSYMBOLPARAMETER

ELECTRICAL CHARACTERISTICS (continued)

(VDD= 2.8V to 7V for MAX951/MAX952, VDD= 2.4V to 7V for MAX953/MAX954, VSS= 0V, V

CM COMP

= 0V for the MAX953/MAX954,

V

CM OPAMP

= 0V, AMPOUT = (VDD+ VSS) / 2, COMPOUT = low, TA= T

MIN

to T

MAX

, typical values are at TA= +25°C, unless

otherwise noted.)

Note 1: Supply current is tested with COMPIN+ = (REF - 100mV) for MAX951/MAX952, and COMPIN+ = 0V for MAX953/MAX954.
Note 2: Input Offset Voltage is defined as the center of the input-referred hysteresis. V

CM COMP

= REF for MAX951/MAX952, and

V

CM COMP

= 0V 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. V

CM COMP

= REF for

MAX951/MAX952, and V

CM COMP

= 0V 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 V

SS

.

Note 5: Reference voltage is measured with respect to VSS. Contact factory for availability of a 3% accurate reference voltage in the

µMAX package.

I

SRC

Output Source Current µA

I

SNK

Output Sink Current µA

MAX951–MAX954

Ultra-Low-Power, Single-Supply

Op Amp + Comparator + Reference

_______________________________________________________________________________________

5

0

2 3 5 7

SUPPLY CURRENT

vs. SUPPLY VOLTAGE

2

8

MAX951–954-01

SUPPLY VOLTAGE (V)

SUPPLY CURRENT (µA)

4 62.5 3.5 5.54.5 6.5

6

4

1

3

9

7

5

V

CM OPAMP

= 0V

AMPOUT = (V

DD

+ VSS)/2
COMP- = 1.2V or REF
COMP+ = 1.1V

MAX953/MAX954

MAX951/MAX952

10

0

-60 -20 60 140

SUPPLY CURRENT

vs. TEMPERATURE

2

8

MAX951–954-02

TEMPERATURE (°C)

SUPPLY CURRENT (µA)

20 100-40 0 8040 120

6

4

1

3

9

7

5

V

DD

= 2.8V (MAX951/2), V

DD

= 2.4V

(MAX953/4), V

SS

= 0V, V

CM OPAMP

= 0V

AMPOUT = 1/2 V

DD

, COMP- = 1.2V or REF

COMP+ = 1.1V

MAX951/MAX952

MAX953/MAX954

1.220

1.180

1.185

-60 -20-40 6040 140120

REFERENCE VOLTAGE vs. TEMPERATURE

1.190

1.215

MAX951-03

TEMPERATURE (°C)

REFERENCE VOLTAGE (V)

200 10080

1.205

1.210

1.195

1.200

VDD = 5V

1.30

1.10

1.12

1 10 100

REFERENCE OUTPUT VOLTAGE

vs. LOAD CURRENT

1.14

1.16

MAX951–954-04

LOAD CURRENT (µA)

REFERENCE VOLTAGE (V)

1.18

1.20

1.22

1.24

1.26

1.28

V

SUPPLY

= 5V

SINKING CURRENT

SOURCING CURRENT

1x10

6

1x10

0

-60 -40 -20 0 20 40 60 80 100 120 140

DC OPEN-LOOP GAIN vs. TEMPERATURE

1x10

1

MAX951-07

TEMPERATURE (°C)

DC OPEN-LOOP GAIN (V/V)

1x10

2

1x10

3

1x10

5

1x10

4

VDD = 5V
1mHz INPUT SIGNAL
R

L

= 100kΩ

0

10

20

30

40

50

60

70

80

1x10

0

1x1011x1021x1031x1041x1051x10

6

POWER-SUPPLY REJECTION

RATIO vs. FREQUENCY

MAX951–954-05

FREQUENCY (Hz)

PSRR (dB)

V

DD

= 2.0 to 3.0V, V

SS

= -2.5V
NONINVERTING
AMPIN+ = 0V
A

CL

= 1V/V (MAX951/2)

A

CL

= 10V/V (MAX953/4),
COMP- = 1.2V or REF
COMP+ = 1.1V from V

SS

A

B

C

A: MAX951/952 REF
B: MAX951/953 OP AMP
C: MAX952/954 OP AMP

2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7

DC OPEN-LOOP GAIN vs.

SUPPLY VOLTAGE

MAX951-06

SUPPLY VOLTAGE (V)

DC OPEN-LOOP GAIN (V/V)

1mHz INPUT SIGNAL
R

L

= 100kΩ

1x10

7

1x10

0

1x10

1

1x10

2

1x10

3

1x10

6

1x10

5

1x10

4

100

-20
1 10 100 1k 10k 100k 1M

MAX951/MAX953 OPEN-LOOP GAIN

AND PHASE vs. FREQUENCY

0

MAX951-08

FREQUENCY (Hz)

OPEN-LOOP GAIN (dB)

20

40

60

80

0

-360

-300

-240

-180

-120

-60

GAIN

RL = 100kΩ

PHASE

PHASE SHIFT (Degrees)

100

-40
1 10 100 1k 10k 100k 1M

MAX952/MAX954 OPEN-LOOP GAIN

AND PHASE vs. FREQUENCY

-20

MAX951-09

FREQUENCY (Hz)

OPEN-LOOP GAIN (dB)

PHASE SHIFT (Degrees)

0

20

40

80

60

RL = 100kΩ

GAIN

PHASE

0

-360

-300

-240

-180

-120

-60

__________________________________________Typical Operating Characteristics

(TA = +25°C, unless otherwise noted.)

COMPARATOR SHORT-CIRCUIT

CURRENT vs. SUPPLY VOLTAGE

MAX951-4 TOC-22

-50

0

100

50

150

200

250

SHORT-CIRCUIT CURRENT (mA)

SUPPLY VOLTAGE (V)

SOURCING CURRENT

SINKING CURRENT

2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7

MAX951–MAX954

Ultra-Low-Power, Single-Supply
Op Amp + Comparator + Reference

6 _______________________________________________________________________________________

____________________________Typical Operating Characteristics (continued)

(TA = +25°C, unless otherwise noted.)

1 10 20001000100

OP-AMP OUTPUT VOLTAGE

vs. LOAD CURRENT

MAX951–4 TOC-10A

A, D: V

SUPPLY

= ±1.5V

B, E: V

SUPPLY

= ±2.5V

C, F: V

SUPPLY

= ±3.5V

SOURCING CURRENT

SINKING CURRENT

NONINVERTING
AMPIN+ = GND

D

E

F

A B

C

-0.10

-0.08

-0.06

-0.04

-0.02

0.02

0.04

0.06

0.08

0.10

0.10

OUTPUT VOLTAGE (V)

LOAD CURRENT (µA)

OP-AMP SHORT-CIRCUIT CURRENT

vs. SUPPLY VOLTAGE

MAX951–4 TOC-11

NONINVERTING
AMPIN+ =(V

DD

- VSS)/2

SHORT TO VSS

SHORT TO V

DD

-1000

-500

500

0

1000

1500

2000

2.5 3 3.5 4 4.5 5 5.5 6 6.5 7

OUTPUT CURRENT (µA)

SUPPLY VOLTAGE (V)

OP AMP PERCENT OVERSHOOT

vs. CAPACITIVE LOAD

MAX951–4 TOC-12

A

D

E

F

C

B

MAX951/3 A = 1V/V
MAX952/4 A = 10V/V

AMPOUT = 1V

PP

VCM = (VDD - VSS/2)

0

10

20

30

40

50

60

70

80

90

100

OVERSHOOT (%)

10110

2

10

3

10410510

6

CAPACITIVE LOAD (pF)

PARTS V

SUPPLY

A: MAX951/2 3V
B: MAX951/3 5V
D: MAX952/4 3V
E: MAX952/4 5V

0.01 10.1 10 200100

COMPARATOR OUTPUT VOLTAGE

vs. LOAD CURRENT

MAX951–4 TOC-15

V

SUPPLY

= 5V

SOURCING CURRENT

SINKING CURRENT

0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

OUTPUT VOLTAGE (V)

LOAD CURRENT (mA)

MAX951–MAX954

Ultra-Low-Power, Single-Supply

Op Amp + Comparator + Reference

_______________________________________________________________________________________

7

MAX951/MAX953 OP-AMP

SMALL-SIGNAL TRANSIENT RESPONSE

2.5V

50mV/div

NONINVERTING, A

VCL

= 1V/V, LOAD = 100kΩ || 100pF to VSS, V

SUPPLY

= 5V

OUTPUT INPUT

100µs/div

200mV/div

MAX951/MAX953 OP-AMP

LARGE-SIGNAL TRANSIENT RESPONSE

2.5V

1V/div

NONINVERTING, A

VCL

= 1V/V, LOAD = 100kΩ || 100pF to VSS, V

SUPPLY

= 5V

OUTPUT INPUT

200µs/div

2V/div

MAX952/MAX954 OP-AMP

SMALL-SIGNAL TRANSIENT RESPONSE

2.5V

50mV/div

NONINVERTING, A

VCL

= 10V/V, LOAD = 100kΩ || 100pF to VSS, V

SUPPLY

= 5V

OUTPUT INPUT

100µs/div

20mV/div

MAX952/MAX954 OP-AMP

LARGE-SIGNAL TRANSIENT RESPONSE

2.5V

1V/div

NONINVERTING, A

VCL

= 10V/V, LOAD = 100kΩ || 100pF to VSS, V

SUPPLY

= 5V

OUTPUT INPUT

100µs/div

200mV/div

____________________________Typical Operating Characteristics (continued)

(TA = +25°C, unless otherwise noted.)

COMPARATOR RESPONSE TIME

FOR VARIOUS INPUT OVERDRIVES (FALLING)

0V

100mV/div

MAX953, LOAD = 100kΩ || 100pF, V

SUPPLY

= 5V

INPUT OUTPUT

0V

2µs/div

1V/div

100mV

50mV

20mV

10mV

COMPARATOR RESPONSE TIME

FOR VARIOUS INPUT OVERDRIVES (RISING)

0V

1V/div

MAX953, LOAD = 100kΩ || 100pF, V

SUPPLY

= 5V

OUTPUT INPUT

0V

2µs/div

100mV/div

100mV

50mV

20mV

10mV

MAX951–MAX954

_______________Detailed Description

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.

Op Amp

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 inputs and a common­mode 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.

Comparator

The comparator in the MAX951–MAX954 has a high­impedance differential input stage with a common­mode 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

Ultra-Low-Power, Single-Supply
Op Amp + Comparator + Reference

8 _______________________________________________________________________________________

______________________________________________________________Pin Description

COMPIN-6—

COMPOUT77

V

DD

88

AMPIN+33

V

SS

44

COMPIN+55

REF—6

AMPIN-22

AMPOUT11

NAME

MAX953
MAX954

MAX951
MAX952

PIN

Inverting Comparator Input
Comparator Output
Positive Supply

Noninverting Op-Amp Input
Negative Supply or Ground
Noninverting Comparator Input

1.200V Reference Output. Also connected to inverting comparator input.

Inverting Op-Amp Input

Op-Amp Output

FUNCTION

Figure 1. MAX951–MAX954 Functional Diagrams

MAX951
MAX952

4

V

DD

8

COMPOUT 7

x1

REF 6

COMPIN+ 5

V

SS

1.20V

3 AMPIN+

2 AMPIN-

1

AMPOUT

OP AMP

COMP

MAX953
MAX954

4

V

DD

8

COMPOUT 7

COMPIN- 6

COMPIN+ 5

V

SS

3 AMPIN+

2 AMPIN-

1

AMPOUT

OP AMP

COMP

continuously source as much as 40mA. The compara­tors eliminate power-supply 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 ESD-protection
diodes and should be avoided.

The MAX951–MAX954 comparator outputs swing rail to
rail (from VDDto VSS). TTL compatibility is assured by
using a +5V ±10% supply.

The MAX951–MAX954 comparator continuously outputs
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 proportional­to-absolute-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.

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 V

REF

/ R2 or 500nA.

2) Choose the width of the hysteresis band. In this
example choose V

EHYST

= 50mV.

where the internal hysteresis is V

IHYST

= 3mV.

3) Determine R1. If the supply voltage is 5V, then R1 =
24kΩ.

4) Check the hysteresis trip points. The upper trip point is

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 R

A

:

MAX951–MAX954

Ultra-Low-Power, Single-Supply

Op Amp + Comparator + Reference

_______________________________________________________________________________________ 9

REF

RB

RA

V

S

R2

COMPOUT

REF

R1

V

IN

R2

COMPOUT

Figure 2. External Hysteresis

R1 R2

V 2

V 2

EHYST IHYST

DD IHYST

=

−

[ ]

+

( )

VV

V

R1 + R2

R2

V V

IN H REF IHYST( )

=

( )

( )

+

MAX951–MAX954

In the example, RAis again 24kΩ.

6) Select the upper trip point V

S(H)

. Our example is set

at 4.75V.

7) Calculate RB.

RBis 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.

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. Low-power, 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.

R

V V R R

R V V V R R

B

REF IHYST A

S H REF IHSYT A

=

+

( ) ( )( )

( )







− +

( )+( )

( )

2

2 2

R R

V

V

for V V

A

SHYST

DD

SHYST IHYST

≈ >>2 ,

Ultra-Low-Power, Single-Supply
Op Amp + Comparator + Reference

10 ______________________________________________________________________________________

R2

R1

2pF to 10pF

AMPOUT

AMPIN+

Figure 3. Compensation for Feedback-Node Capacitance

Figure 4. Low-Frequency Radio Receiver Application

ANTENNA

V

= 5V

CC

0.1µF

C1

A

390pF

C1

B

C1

330pF

)

C

C

20-60pF

2

LAYOUT-SENSITIVE AREA,
METAL RFI SHIELDING ADVISED

L1
330mH

1

L1 x C1 =

(2π f

MAX952

AMP

1.0M
100k

5.1M

0.1µF
20k

1.2V

10M

COMP

REF

Power-Supply Bypassing

Power-supply bypass capacitors are not required if the
supply impedance is low. For single-supply applications,
it is good general practice to bypass VDDwith a. 0.1µF
capacitor to ground. Do not bypass the reference output.

________________Application Circuits

Low-Frequency Radio Receiver for

Alarms and Detectors

Figure 4’s circuit 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 C1Cin 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 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.

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 amp 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

MAX951–MAX954

Ultra-Low-Power, Single-Supply

Op Amp + Comparator + Reference

______________________________________________________________________________________ 11

REF

0.1µF

0.1µF

1

2π f

C

10M

100k

1.2V

30k

V

CC

= 5V

COMP

AMP

C2

15pF, 5%

10kHz,
5Vp-p

C1
150pF,
5%

NEC
PH302B

NEC

SE307-C

51Ω

R1

A

49.9k
1%

R1

B

49.9k
1%

R2

1.0M,
1%

LAYOUT-SENSITIVE AREA

MAX952

R1 x C1 = R2 x C2 =

Figure 5. Infrared Receiver Application Figure 6. Sensor Preamp and Alarm Trigger Application

MAX953

V

CC

RADIOACTIVE
IONIZATION
CHAMBER
SMOKE SENSOR

LAYOUT-SENSITIVE AREA

AMP

4.7M

5.1M

COMP

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.

0.084"

(2.134mm)

0.058"

(1.473mm)

V

DD

V

SS

COMPOUT

REF(COMPIN-)

COMPIN+

AMPIN+

( ) ARE FOR MAX953/MAX954

AMPIN-

AMPOUT

MAX951–MAX954

Ultra-Low-Power, Single-Supply
Op Amp + Comparator + Reference

______________Ordering Information

___________________Chip Topography

PART

MAX951C/D

0°C to +70°C

TEMP. RANGE PIN-PACKAGE

Dice*

* Dice are tested at TA= +25°C, DC parameters only.
** Contact factory for availability and processing to MIL-STD-883.

TRANSISTOR COUNT: 163
SUBSTRATE CONNECTED TO V

DD

3

AMPIN+

INPUT

2

5

6

1

8

4

REF

0.1µF

1.20V

V

SS

V

CC

R1

R2

1M

COMPOUT
7

MAX951
MAX952

__________Typical Operating Circuit

MAX951EPA -40°C to +85°C 8 Plastic DIP

MAX951MJA -55°C to +125°C 8 CERDIP**

MAX951ESA -40°C to +85°C 8 SO

MAX952C/D

0°C to +70°C Dice*

MAX952EPA -40°C to +85°C 8 Plastic DIP

MAX952MJA -55°C to +125°C 8 CERDIP**

MAX952ESA -40°C to +85°C 8 SO

MAX953C/D

0°C to +70°C

MAX954C/D

0°C to +70°C

Dice*

MAX953EPA -40°C to +85°C 8 Plastic DIP

MAX953MJA -55°C to +125°C 8 CERDIP**

Dice*

MAX954EPA -40°C to +85°C 8 Plastic DIP

MAX954MJA -55°C to +125°C 8 CERDIP**

MAX954ESA -40°C to +85°C 8 SO

MAX953ESA -40°C to +85°C 8 SO

MAX951EUA -40°C to +85°C 8 µMAX

MAX952EUA -40°C to +85°C 8 µMAX

MAX953EUA -40°C to +85°C 8 µMAX

MAX954EUA -40°C to +85°C 8 µMAX

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.

12

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