Rainbow Electronics MAX4040, MAX4044 User Manual

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________________General Description

The MAX4040–MAX4044 family of micropower op amps
operates from a single +2.4V to +5.5V supply or dual
±1.2V to ±2.75V supplies and have Rail-to-Rail®input
and output capabilities. These amplifiers provide a
90kHz gain-bandwidth product while using only 10µA of
supply current per amplifier. The MAX4041/MAX4043
have a low-power shutdown mode that reduces supply
current to less than 1µA and forces the output into a
high-impedance state. The combination of low-voltage
operation, rail-to-rail inputs and outputs, and ultra-low
power consumption makes these devices ideal for any
portable/battery-powered system.

These amplifiers have outputs that typically swing to
within 10mV of the rails with a 100kΩ load. Rail-to-rail
input and output characteristics allow the full power­supply voltage to be used for signal range. The combi­nation of low input offset voltage, low input bias current,
and high open-loop gain makes them suitable for low­power/low-voltage precision applications.

The MAX4040 is offered in a space-saving 5-pin SOT23
package. All specifications are guaranteed over the

-40°C to +85°C extended temperature range.

________________________Applications

Battery-Powered Strain Gauges
Systems

Sensor Amplifiers

Portable/Battery-Powered Cellular Phones
Electronic Equipment

Notebook Computers

Digital Scales PDAs

____________________________Features

♦ Single-Supply Operation Down to +2.4V
♦ Ultra-Low Power Consumption:

10µA Supply Current per Amplifier
1µA Shutdown Mode (MAX4041/MAX4043)

♦ Rail-to-Rail Input Common-Mode Range
♦ Outputs Swing Rail-to-Rail
♦ No Phase Reversal for Overdriven Inputs
♦ 200µV Input Offset Voltage
♦ Unity-Gain Stable for Capacitive Loads up to 200pF
♦ 90kHz Gain-Bandwidth Product
♦ Available in Space-Saving 5-Pin SOT23 and

8-Pin µMAX Packages

MAX4040–MAX4044

Single/Dual/Quad, Low-Cost, SOT23,

Micropower Rail-to-Rail I/O Op Amps

________________________________________________________________

Maxim Integrated Products

1

V

EE

IN-IN+

15V

CC

OUT

MAX4040

SOT23-5

TOP VIEW

2

34

19-1377; Rev 0; 5/98

PART

MAX4040EUK-T

MAX4040EUA
MAX4040ESA -40°C to +85°C

-40°C to +85°C

-40°C to +85°C

TEMP. RANGE

PIN-

PACKAGE

5 SOT23-5
8 µMAX
8 SO

Ordering Information

Pin Configurations continued at end of data sheet.

NO. OF

AMPS

PIN-PACKAGE

MAX4040 1

5-pin SOT23,
8-pin µMAX/SO

PART

MAX4041 1 8-pin µMAX/SO

SHUTDOWN

—

Yes

MAX4044 4 14-pin SO—

Rail-to-Rail is a registered trademark of Nippon Motorola Ltd.

MAX4042EUA
MAX4042ESA -40°C to +85°C

-40°C to +85°C 8 µMAX
8 SO

MAX4044ESD

-40°C to +85°C 14 SO

SOT

TOP MARK

ACGF

—
—

—
—

—

Pin Configurations

Selector Guide

MAX4042 2 8-pin µMAX/SO—

MAX4043 2

10-pin µMAX/
14-pin SO

Yes

MAX4041ESA
MAX4041EUA -40°C to +85°C

-40°C to +85°C 8 SO
8 µMAX

—
—

MAX4043EUB
MAX4043ESD -40°C to +85°C

-40°C to +85°C 10 µMAX
14 SO

—
—

MAX4040–MAX4044

Single/Dual/Quad, Low-Cost, SOT23,
Micropower, Rail-to-Rail I/O Op Amps

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS—T

A

= +25°C

(VCC= +5.0V, VEE= 0, VCM= 0, V

OUT

= VCC/ 2, SHDN = VCC, RL= 100kΩ tied to VCC/ 2, 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 (VCCto VEE)..................................................+6V

All Other Pins ...................................(V

CC

+ 0.3V) to (VEE- 0.3V)

Output Short-Circuit Duration to V

CC

or VEE..............Continuous

Continuous Power Dissipation (T

A

= +70°C)

5-Pin SOT23 (derate 7.1mW/°C above +70°C).............571mW

8-Pin µMAX (derate 4.1mW/°C above +70°C)..............330mW

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

10-Pin µMAX (derate 5.6mW/°C above +70°C)...........444mW

14-Pin SO (derate 8.33mW/°C above +70°C)..............667mW

Operating Temperature Range ...........................-40°C to +85°C

Junction Temperature......................................................+150°C

Storage Temperature Range.............................-65°C to +160°C

Lead Temperature (soldering, 10sec).............................+300°C

14 20VCC= 5.0V

VEE≤ VCM≤ V

CC

Input Offset Current I

OS

±0.5 ±3.0 nA

VEE≤ VCM≤ V

CC



V

IN+

- V

IN-



< 1.0V

Differential Input
Resistance

R

IN(DIFF)

45 MΩ

2.0 5.0



V

IN+

- V

IN-



> 2.5V

SHDN = VEE, MAX4041
and MAX4043 only

Large-Signal
Voltage Gain

Shutdown Supply
Current per Amplifier

I

CC(SHDN)

1.0

Supply-Voltage Range V

CC

2.4 5.5 VInferred from PSRR test

Output Voltage
Swing High

4.4 kΩ

V

OH

Inferred from the CMRR test

mV

A

VOL

dB

PARAMETER SYMBOL MIN TYP MAX UNITS

Supply Current
per Amplifier

I

CC

10

µA

94

VCC= 2.4V

10

Specified as VCC- V

OH



Power-Supply
Rejection Ratio

PSRR dB

(VEE+ 0.2V) ≤ V

OUT

≤ (VCC- 0.2V)

60 90

74 85

Output Voltage
Swing Low

Input Common-Mode
Voltage Range

RL= 100kΩ
RL= 25kΩ

RL= 100kΩ
RL= 25kΩ

µA

V

CM

V

EE

V

CC

V

2.4V ≤ VCC≤ 5.5V 75 85

VCC= 2.4V

V

OL

mV

10

Specified as VEE- V

OL



Input Bias Current I

B

±2 ±10 nA

40 60

RL= 100kΩ
RL= 25kΩ

Output Short-Circuit
Current

I

OUT(SC)

mA

0.7Sourcing

2.5

Channel-to-Channel
Isolation

Sinking

dB

CONDITIONS

80Specified at DC, MAX4042/MAX4043/MAX4044 only

VCC= 5.0V

±0.20 ±2.0

V

OS

Input Offset Voltage

mV

±0.25 ±2.5

VEE≤ VCM≤ V

CC

70 94

dBCMRR

Common-Mode
Rejection Ratio

MAX404_EU_
All other packages

65 94

VEE≤ VCM≤ V

CC

MAX4044ESD
MAX404_EU_
All other packages mV±0.20 ±1.50

Single/Dual/Quad, Low-Cost, SOT23,

Micropower, Rail-to-Rail I/O Op Amps

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS—TA= +25°C (continued)

(VCC= +5.0V, VEE= 0, VCM= 0, V

OUT

= VCC/ 2, SHDN = VCC, RL= 100kΩ tied to VCC/ 2, unless otherwise noted.)

MAX4040–MAX4044

PARAMETER SYMBOL MIN TYP MAX UNITSCONDITIONS

Supply Current
per Amplifier

I

CC

28

Supply-Voltage Range V

CC

2.4 5.5 VInferred from PSRR test

VEE≤ VCM≤ V

CC

Input Offset Current I

OS

±8 nA

Input Voltage Noise Density e

n

70

nV/√Hz

Input Current Noise Density i

n

0.05

pA/√Hz
Capacitive-Load Stability 200 pF
Power-Up Time t

ON

200 µs

Input Capacitance C

IN

3 pF

f = 1kHz
f = 1kHz
A

VCL

= +1V/V, no sustained oscillations

Slew Rate SR 40 V/ms

Total Harmonic Distortion THD 0.05 %
Settling Time to 0.01% t

S

50 µs

fIN= 1kHz, V

OUT

= 2Vp-p, AV= +1V/V

AV= +1V/V, V

OUT

= 2V

STEP

PARAMETER SYMBOL MIN TYP MAX UNITSCONDITIONS

Gain Margin G

m

18 dB

Output Leakage Current in
Shutdown

I

OUT(SHDN)

20 100 nA

SHDN = VEE= 0, MAX4041/MAX4043 only
(Note 1)

µA

6.0

SHDN = VEE, MAX4041 and MAX4043 only

Shutdown Supply
Current per Amplifier

I

CC(SHDN)

µA

Shutdown Time t

SHDN

50 µsMAX4041 and MAX4043 only

Enable Time from Shutdown t

EN

150 µsMAX4041 and MAX4043 only

ELECTRICAL CHARACTERISTICS—TA= T

MIN

to

T

MAX

(VCC= +5.0V, VEE= 0, VCM= 0, V

OUT

= VCC/ 2, SHDN = VCC, RL= 100kΩ tied to VCC/ 2, unless otherwise noted.) (Note 2)

Input Offset Voltage Drift TC

VOS

2 µV/°C

VEE≤ VCM≤ V

CC

Input Bias Current I

B

±20 nA

Phase Margin

Φ

m

68 degrees

±4.5

SHDN Logic Low

V

IL

0.3 x V

CC

VMAX4041/MAX4043 only

SHDN Logic High

V

IH

0.7 x V

CC

VMAX4041/MAX4043 only

SHDN Input Bias Current

IIH, I

IL

40 120 nAMAX4041/MAX4043 only

Gain Bandwidth Product GBW 90 kHz

±5.0V

OS

Input Offset Voltage mV

±3.5

VEE≤ VCM≤ V

CC

MAX4044ESA

All other packages

MAX404_EU_

20

0

-60 -40 -20 20

40

100

SUPPLY CURRENT PER AMPLIFIER

vs. TEMPERATURE

6
4
2

16
14

18

MAX4040/44-01

TEMPERATURE (°C)

SUPPLY CURRENT (µA)

0 60

10

8

12

80

VCC = +5.5V

VCC = +2.4V

5

0

-60 -40 -20

0

20 40 100

MAX4041/MAX4043

SHUTDOWN SUPPLY CURRENT

PER AMPLIFIER vs. TEMPERATURE

1

4

MAX4040/44-01.5

TEMPERATURE (°C)

SHUTDOWN SUPPLY CURRENT (µA)

60

2

3

80

VCC = +5.5V

SHDN = 0

VCC = +2.4V

__________________________________________Typical Operating Characteristics

(VCC= +5.0V, VEE= 0, VCM= V

CC

/ 2, SHDN = VCC, RL= 100kΩ to V

CC

/ 2, TA= +25°C, unless otherwise noted.)

MAX4040–MAX4044

Single/Dual/Quad, Low-Cost, SOT23,
Micropower, Rail-to-Rail I/O Op Amps

4 _______________________________________________________________________________________

Large-Signal Voltage
Gain

Output Voltage Swing
High

V

OH

Inferred from the CMRR test

mV

A

VOL

dB

PARAMETER SYMBOL MIN TYP MAX UNITS

Specified as VCC- V

OH



, R

L

= 25kΩ

Common-Mode
Rejection Ratio

CMRR dB

(VEE+ 0.2V) ≤ V

OUT

≤ (VCC- 0.2V), RL= 25kΩ

125

68

Output Voltage Swing
Low

Input Common-Mode
Voltage Range

V

CM

V

EE

V

CC

V

60

V

OL

mV

Specified as VEE- V

OL



, R

L

= 25kΩ

75

CONDITIONS

ELECTRICAL CHARACTERISTICS—TA= T

MIN

to

T

MAX

(continued)

(VCC= +5.0V, VEE= 0, VCM= 0, V

OUT

= VCC/ 2, SHDN = VCC, RL= 100kΩ tied to VCC/ 2, unless otherwise noted.) (Note 2)

Note 1: Tested for V

EE

≤ V

OUT

≤ VCC. Does not include current through external feedback network.

Note 2: All devices are 100% tested at T

A

= +25°C. All temperature limits are guaranteed by design.

Power-Supply
Rejection Ratio

PSRR dB2.4V ≤ VCC≤ 5.5V 70

MAX404_EU_

VEE≤ VCM≤ V

CC

All other packages 65

MAX4040–MAX4044

Single/Dual/Quad, Low-Cost, SOT23,

Micropower, Rail-to-Rail I/O Op Amps

_______________________________________________________________________________________ 5

120

0

-60 -40 -20 20

40

100

OUTPUT SWING HIGH

vs. TEMPERATURE

20

100

80

MAX4040/44-07

TEMPERATURE (°C)

VOLTAGE FROM V

CC

(mV)

0 60

60

40

80

VCC = +2.4V, RL = 10kΩ

RL TO V

EE

VCC = +5.5V, RL = 20kΩ

VCC = +5.5V, RL = 100kΩ

VCC = +2.4V, RL = 100kΩ

120

0

-60 -40 -20 20

40

100

OUTPUT SWING LOW

vs. TEMPERATURE

20

100

80

MAX4040/44-08

TEMPERATURE (°C)

VOLTAGE FROM V

EE

(mV)

0 60

60

40

80

VCC = +2.4V, RL = 10kΩ

VCC = +5.5V, RL = 20kΩ

VCC = +5.5V, RL = 100kΩ

VCC = +2.4V, RL = 100kΩ

RL TO V

CC

-80

-100

-60 -40 -20 20

40

100

COMMON-MODE REJECTION

vs. TEMPERATURE

-95

-85

MAX4040/44-09

TEMPERATURE (°C)

COMMON-MODE REJECTION (dB)

0 60

-90

80

VCC = +2.4V

VCC = +5.5V

0

-4

-60 -40 -20 20

40

100

INPUT BIAS CURRENT

vs. TEMPERATURE

-3

-1

MAX4040/44-04

TEMPERATURE (°C)

INPUT BIAS CURRENT (nA)

0 60-280

VCM = 0

VCC = +2.4V

VCC = +5.5V

5.0

-5.0
0 0.2

0.6 1.0 1.4

INPUT BIAS CURRENT vs.

COMMON-MODE VOLTAGE (V

CC

= 2.4V)

-2.5

2.5

MAX4040/44-5

VCM (V)

I

BIAS

(nA)

0

1.8

2.2

V

CC

= +2.4V

5.0

-5.0
0 0.5

1.5

2.5 3.5

4.5

INPUT BIAS CURRENT vs.

COMMON-MODE VOLTAGE (V

CC

= 5.5V)

-2.5

2.5

MAX4040/44-06

VCM (V)

I

BIAS

(nA)

0

5.5

V

CC

= +5.5V

400

0

-60 -40 -20 20

40

100

INPUT OFFSET VOLTAGE

vs. TEMPERATURE

100

300

MAX4040/44-03

TEMPERATURE (°C)

INPUT OFFSET VOLTAGE (µV)

0 60

200

80

Typical Operating Characteristics (continued)

(VCC= +5.0V, VEE= 0, VCM= V

CC

/ 2, SHDN = VCC, RL= 100kΩ to V

CC

/ 2, TA= +25°C, unless otherwise noted.)

MAX4040–MAX4044

Single/Dual/Quad, Low-Cost, SOT23,
Micropower, Rail-to-Rail I/O Op Amps

6 _______________________________________________________________________________________

100

30

0 100 300 500

OPEN-LOOP GAIN vs. OUTPUT SWING LOW

(V

CC

= +2.4V, RL TIED TO VCC)

50

40

90

80

MAX4040/44-10

∆V

OUT

(mV)

GAIN (dB)

200 400

70
60

RL = 100kΩ

RL = 10kΩ

100

110

0 100 200 300 400

OPEN-LOOP GAIN vs. OUTPUT SWING HIGH

(V

CC

= +5.5V, RL TIED TO VEE)

50

40

90

80

MAX4040/44-13

∆V

OUT

(mV)

GAIN (dB)

70
60

RL = 20kΩ

RL = 100kΩ

100

30

0 100 300 500

OPEN-LOOP GAIN vs. OUTPUT SWING HIGH

(V

CC

= +2.4V, RL TIED TO VEE)

50

40

90

80

MAX4040/44-11

∆V

OUT

(mV)

GAIN (dB)

200 400

70
60

RL = 100kΩ

RL = 10kΩ

100

110

0 100 200 300 400

OPEN-LOOP GAIN vs. OUTPUT SWING LOW

(V

CC

= +5.5V, RL TIED TO VCC)

50

40

90

80

MAX4040/44-12

∆V

OUT

(mV)

GAIN (dB)

70
60

RL = 100kΩ

RL = 20kΩ

110

70

-60 -40 -20 20

40

100

OPEN-LOOP GAIN

vs. TEMPERATURE

75

80

105
100

95

MAX4040/44-14

TEMPERATURE (°C)

GAIN (dB)

0 60

90
85

80

VCC = +5.5V, RL = 20kΩ TO V

CC

VCC = +5.5V, RL = 20kΩ TO V

EE

VCC = +2.4V, RL = 10kΩ TO V

EE

VCC = +2.4V, RL = 10kΩ TO V

CC

110

70

-60 -40 -20 20

40

100

OPEN-LOOP GAIN

vs. TEMPERATURE

75

80

105
100

95

MAX4040/44-15

TEMPERATURE (°C)

GAIN (dB)

0 60

90
85

80

VCC = +5.5V, RL TO V

CC

VCC = +5.5V, RL TO V

EE

VCC = +2.4V, RL TO V

CC

VCC = +2.4V, RL TO V

EE

____________________________________Typical Operating Characteristics (continued)

(VCC= +5.0V, VEE= 0, VCM= V

CC

/ 2, SHDN = VCC, RL= 100kΩ to V

CC

/ 2, TA= +25°C, unless otherwise noted.)

60

-40
10 100 1k 10k 100k

GAIN AND PHASE vs. FREQUENCY

(NO LOAD)

-20

-30

MAX4040/44-16

FREQUENCY (Hz)

GAIN (dB)

0

-10

20

10

30

40

50

180

-180

-108

-144

PHASE (DEGREES)

-36

-72

36
0

72

108

144

AV = +1000V/V

60

-40
10 100 1k 10k 100k

GAIN AND PHASE vs. FREQUENCY

(C

L

= 100pF)

-20

-30

MAX4040/44-17

FREQUENCY (Hz)

GAIN (dB)

0

-10

20
10

30

40

50

180

-180

-108

-144

PHASE (DEGREES)

-36

-72

36
0

72

108

144

AV = +1000V/V

MAX4040–MAX4044

Single/Dual/Quad, Low-Cost, SOT23,

Micropower, Rail-to-Rail I/O Op Amps

_______________________________________________________________________________________

7

____________________________________Typical Operating Characteristics (continued)

(VCC= +5.0V, VEE= 0, VCM= V

CC

/ 2, SHDN = VCC, RL= 100kΩ to V

CC

/ 2, TA= +25°C, unless otherwise noted.)

1

0.01
1 100010010

TOTAL HARMONIC DISTORTION PLUS NOISE

vs. FREQUENCY

0.1

MAX4040/44-19

FREQUENCY (Hz)

THD + NOISE (%)

RL = 10kΩ

RL = 100kΩ

1000

10

0 250 500 1000

LOAD RESISTOR vs.

CAPACITIVE LOAD

MAX4040/44-20

C

LOAD

(pF)

R

LOAD

(kΩ)

750

100

10%

OVERSHOOT

REGION OF

MARGINAL STABILITY

REGION OF

STABLE OPERATION

10µs/div

SMALL-SIGNAL TRANSIENT RESPONSE

(NONINVERTING)

MAX4040/44-21

50mV/div

100mV

100mV

IN

OUT

0V

0V

10µs/div

SMALL-SIGNAL TRANSIENT RESPONSE

(INVERTING)

MAX4040/44-22

50mV/div

100mV

100mV

IN

OUT

0V

0V

100µs/div

LARGE-SIGNAL TRANSIENT RESPONSE

(NONINVERTING)

MAX4040/42/44-23

2V/div

4.5V

0.5V

4.5V

IN

0.5V

OUT

100µs/div

LARGE-SIGNAL TRANSIENT RESPONSE

(INVERTING)

MAX4040/42/44-24

2V/div

+2V

-2V

-2V

+2V

IN

OUT

-60

-110
10 1k 10k

100

MAX4042/MAX4043/MAX4044

CROSSTALK vs. FREQUENCY

-100

MAX4040/44-18

FREQUENCY (Hz)

GAIN (dB)

-90

-80

-70

RL = 10kΩ

MAX4040–MAX4044

Single/Dual/Quad, Low-Cost, SOT23,
Micropower, Rail-to-Rail I/O Op Amps

8 _______________________________________________________________________________________

_______________Detailed Description

Rail-to-Rail Input Stage

The MAX4040–MAX4044 have rail-to-rail inputs and
rail-to-rail output stages that are specifically designed
for low-voltage, single-supply operation. The input
stage consists of separate NPN and PNP differential
stages, which operate together to provide a common­mode range extending to both supply rails. The
crossover region of these two pairs occurs halfway
between VCCand VEE. The input offset voltage is typi­cally 200µV. Low operating supply voltage, low supply
current, rail-to-rail common-mode input range, and rail­to-rail outputs make this family of operational amplifiers

an excellent choice for precision or general-purpose,
low-voltage battery-powered systems.

Since the input stage consists of NPN and PNP pairs,
the input bias current changes polarity as the common­mode voltage passes through the crossover region.
Match the effective impedance seen by each input to
reduce the offset error caused by input bias currents
flowing through external source impedances (Figures
1a and 1b). The combination of high source impedance
plus input capacitance (amplifier input capacitance
plus stray capacitance) creates a parasitic pole that
produces an underdamped signal response. Reducing
input capacitance or placing a small capacitor across
the feedback resistor improves response in this case.

______________________________________________________________Pin Description

1 —— — —

2 44 4 11

Negative Supply. Tie to ground for
single-supply operation.

V

EE

3 —

Amplifier Output. High impedance
when in shutdown mode.

OUT

— — —

4 —— — — Inverting InputIN-

Noninverting InputIN+

5 108 14 4

— ——

5, 7,

8, 10

—

No Connection. Not internally con­nected.

N.C.

— —

Positive SupplyV

CC

— — —

— 1, 91, 7 1, 13 1, 7

Outputs for Amplifiers A and B. High
impedance when in shutdown mode.

OUTA,

OUTB

Shutdown Input. Drive high, or tie to
VCCfor normal operation. Drive to V

EE

to place device in shutdown mode.

SHDN

— 2, 82, 6 2, 12 2, 6

— 3, 73, 5 3, 11 3, 5

Noninverting Inputs to Amplifiers A
and B

INA+,

INB+

— 5, 6

Inverting Inputs to Amplifiers A and B

INA-,

INB-

— 6, 9 —

— —— — 8, 14 Outputs for Amplifiers C and D

OUTC,

OUTD

Shutdown Inputs for Amplifiers A
and B. Drive high, or tie to V

CC

for
normal operation. Drive to VEEto
place device in shutdown mode.

SHDNA,

SHDNB

— —— — 9, 13

— —— — 10, 12

Noninverting Inputs to Amplifiers C
and D

INC+,

IND+

Inverting Inputs to Amplifiers C and D

INC-,

IND-

6

4
3

2
7

1, 5

8

—

—

—

—

—

—

—

6

4
3

2
7

1, 5, 8

—

—

—

—

—

—

—

—

MAX4043

MAX4044

PIN

µMAX

MAX4042

SO

MAX4041

FUNCTIONNAME

SOT23-5

MAX4040

SO/µMAX

MAX4040–MAX4044

Single/Dual/Quad, Low-Cost, SOT23,

Micropower, Rail-to-Rail I/O Op Amps

_______________________________________________________________________________________ 9

The MAX4040–MAX4044 family’s inputs are protected
from large differential input voltages by internal 2.2kΩ
series resistors and back-to-back triple-diode stacks
across the inputs (Figure 2). For differential input volt­ages (much less than 1.8V), input resistance is typically
45MΩ. For differential input voltages greater than 1.8V,
input resistance is around 4.4kΩ, and the input bias
current can be approximated by the following equation:

I

BIAS

= (V

DIFF

- 1.8V) / 4.4kΩ

In the region where the differential input voltage
approaches 1.8V, the input resistance decreases expo­nentially from 45MΩ to 4.4kΩ as the diode block begins
conducting. Conversely, the bias current increases with
the same curve.

Rail-to-Rail Output Stage

The MAX4040–MAX4044 output stage can drive up to a
25kΩ load and still swing to within 60mV of the rails.
Figure 3 shows the output voltage swing of a MAX4040
configured as a unity-gain buffer, powered from a single
+4.0V supply voltage. The output for this setup typically
swings from (VEE+ 10mV) to (VCC- 10mV) with a 100kΩ
load.

Applications Information

Power-Supply Considerations

The MAX4040–MAX4044 operate from a single +2.4V to
+5.5V supply (or dual ±1.2V to ±2.75V supplies) and
consume only 10µA of supply current per amplifier. A
high power-supply rejection ratio of 85dB allows the
amplifiers to be powered directly off a decaying battery
voltage, simplifying design and extending battery life.

Power-Up Settling Time

The MAX4040–MAX4044 typically require 200µs to
power up after VCCis stable. During this start-up time,
the output is indeterminant. The application circuit
should allow for this initial delay.

R3

R3 = R1 R2

R1 R2

MAX4040–
MAX4044

V

IN

Figure 1b. Minimizing Offset Error Due to Input Bias Current
(Inverting)

2.2k

2.2k

IN-

IN+

Figure 2. Input Protection Circuit

R3

V

IN

R3 = R1 R2

R1 R2

MAX4040–
MAX4044

Figure 1a. Minimizing Offset Error Due to Input Bias Current
(Noninverting)

MAX4040–MAX4044

Single/Dual/Quad, Low-Cost, SOT23,
Micropower, Rail-to-Rail I/O Op Amps

10 ______________________________________________________________________________________

Shutdown Mode

The MAX4041 (single) and MAX4043 (dual) feature a
low-power shutdown mode. When the shutdown pin
(SHDN) is pulled low, the supply current drops to 1µA
per amplifier, the amplifier is disabled, and the outputs
enter a high-impedance state. Pulling SHDN high or
leaving it floating enables the amplifier. Take care to
ensure that parasitic leakage current at the SHDN pin
does not inadvertently place the part into shutdown
mode when SHDN is left floating. Figure 4 shows the
output voltage response to a shutdown pulse. The logic
threshold for SHDN is always referred to V

CC

/ 2 (not to
GND). When using dual supplies, pull SHDN to VEEto
enter shutdown mode.

Load-Driving Capability

The MAX4040–MAX4044 are fully guaranteed over tem­perature and supply voltage to drive a maximum resis­tive load of 25kΩ to VCC/ 2, although heavier loads can
be driven in many applications. The rail-to-rail output
stage of the amplifier can be modeled as a current
source when driving the load toward VCC, and as a cur­rent sink when driving the load toward VEE. The magni­tude of this current source/sink varies with supply
voltage, ambient temperature, and lot-to-lot variations
of the units.

Figures 5a and 5b show the typical current source and
sink capability of the MAX4040–MAX4044 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.

1200

0

-60 -40 -20 100

200

400

1000

MAX4040-44 fig05a

TEMPERATURE (°C)

OUTPUT SOURCE CURRENT (µA)

0 4020

600

800

8060

VCC = 5.5V, VOH = 200mV

VCC = 5.5V, VOH = 100mV

VCC = 2.4V, VOH = 50mV

VCC = 5.5V, VOH = 50mV

VCC = 2.4V,
V

OH

= 200mV

VCC = 2.4V,
V

OH

= 100mV

Figure 5a. Output Source Current vs. Temperature

3000

0

-60 -40 -20 100

500

1000

2500

MAX4040-44 fig05b

TEMPERATURE (°C)

OUTPUT SINK CURRENT (µA)

0 4020

1500

2000

8060

VCC = 5.5V, VOL = 200mV

VCC = 2.4V, VOL = 200mV

VCC = 5.5V,
V

OL

= 100mV

VCC = 2.4V, VOL = 50mV

VCC = 5.5V, VOL = 50mV

VCC = 2.4V, VOL = 100mV

Figure 5b. Output Sink Current vs. Temperature

1V/div

OUT

IN

1V/div

MAX4040-44 fig03

200µs/div

RL = 100kΩ TIED TO V

EE

VIN = 4.0V
f

IN

= 1kHz

Figure 3. Rail-to-Rail Input/Output Voltage Range

MAX4040-44 fig04

200µs/div

5V/div

1V/div

SHDN

OUT

VIN = 2V
R

L

= 100kΩ TIED TO V

EE

Figure 4. Shutdown Enable/Disable Output Voltage

MAX4040–MAX4044

Single/Dual/Quad, Low-Cost, SOT23,

Micropower, Rail-to-Rail I/O Op Amps

______________________________________________________________________________________ 11

For example, a MAX4040 running from a single +2.4V
supply, operating at TA= +25°C, can source 240µA to
within 100mV of VCCand is capable of driving a 9.6kΩ
load resistor to VEE:

The same application can drive a 4.6kΩ load resistor
when terminated in VCC/ 2 (+1.2V in this case).

Driving Capacitive Loads

The MAX4040–MAX4044 are unity-gain stable for loads
up to 200pF (see Load Resistor vs. Capacitive Load
graph in

Typical Operating Characteristics

).
Applications that require greater capacitive drive capa­bility should use an isolation resistor between the output
and the capacitive load (Figures 6a–6c). Note that this
alternative results in a loss of gain accuracy because
R

ISO

forms a voltage divider with the load resistor.

Power-Supply Bypassing and Layout

The MAX4040–MAX4044 family operates from either a
single +2.4V to +5.5V supply or dual ±1.2V 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 V

CC

and VEEsupplies 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 by placing exter­nal components as close as possible to the op amp.
Surface-mount components are an excellent choice.

Using the MAX4040–MAX4044

as Comparators

Although optimized for use as operational amplifiers,
the MAX4040–MAX4044 can also be used as rail-to-rail
I/O comparators. Typical propagation delay depends
on the input overdrive voltage, as shown in Figure 7.
External hysteresis can be used to minimize the risk of
output oscillation. The positive feedback circuit, shown
in Figure 8, causes the input threshold to change when
the output voltage changes state. The two thresholds
create a hysteresis band that can be calculated by the
following equations:

V

HYST

= VHI- V

LO

VLO= VINx R2 / (R1 + (R1 x R2 / R

HYST

) + R2)

VHI= [(R2 / R1 x VIN) + (R2 / R

HYST

) x VCC] /

(1 + R1 / R2 + R2 / R

HYST

)

R =

2.4V - 0.1V
240 A

9.6k to V

L EE

µ

= Ω

50mV/div

IN

OUT

50mV/div

MAX4040/42/44 fig06b

100µs/div

R

ISO

= NONE, RL = 100kΩ, CL = 700pF

Figure 6b. Pulse Response without Isolating Resistor

50mV/div

IN

OUT

50mV/div

MAX4040/42/44 fig06c

100µs/div

R

ISO

= 1kΩ, RL = 100kΩ, CL = 700pF

Figure 6c. Pulse Response with Isolating Resistor

R

ISO

C

L

R

L

MAX4040–
MAX4044

AV =

R

L

≈ 1

R

L

+ R

ISO

Figure 6a. Using a Resistor to Isolate a Capacitive Load from
the Op Amp

MAX4040–MAX4044

Single/Dual/Quad, Low-Cost, SOT23,
Micropower, Rail-to-Rail I/O Op Amps

12 ______________________________________________________________________________________

The MAX4040–MAX4044 contain special circuitry to
boost internal drive currents to the amplifier output
stage. This maximizes the output voltage range over
which the amplifiers are linear. In an open-loop com­parator application, the excursion of the output voltage
is so close to the supply rails that the output stage tran­sistors will saturate, causing the quiescent current to
increase from the normal 10µA. Typical quiescent cur­rents increase to 35µA for the output saturating at V

CC

and 28µA for the output at VEE.

Using the MAX4040–MAX4044

as Ultra-Low-Power Current Monitors

The MAX4040–MAX4044 are ideal for applications pow­ered from a battery stack. Figure 9 shows an application
circuit in which the MAX4040 is used for monitoring the
current of a battery stack. In this circuit, a current load is
applied, and the voltage drop at the battery terminal is
sensed.

The voltage on the load side of the battery stack is
equal to the voltage at the emitter of Q1, due to the
feedback loop containing the op amp. As the load cur­rent increases, the voltage drop across R1 and R2
increases. Thus, R2 provides a fraction of the load cur­rent (set by the ratio of R1 and R2) that flows into the
emitter of the PNP transistor. Neglecting PNP base cur­rent, this current flows into R3, producing a ground-ref­erenced voltage proportional to the load current. Scale
R1 to give a voltage drop large enough in comparison
to VOSof the op amp, in order to minimize errors.

The output voltage of the application can be calculated
using the following equation:

V

OUT

= [I

LOAD

x (R1 / R2)] x R3

For a 1V output and a current load of 50mA, the choice
of resistors can be R1 = 2Ω, R2 = 100kΩ, R3 = 1MΩ.
The circuit consumes less power (but is more suscepti­ble to noise) with higher values of R1, R2, and R3.

R2

R1

V

IN

OUTPUT

INPUT

V

OH

V

OL

V

EE

V

CC

V

OUT

R

HYST

V

EE

MAX4040–
MAX4044

HYSTERESIS

V

LO

V

OH

V

HI

Figure 8. Hysteresis Comparator Circuit

R1

I

LOAD

R2

V

CC

V

EE

R3

V

OUT

Q1

MAX4040

Figure 9. Current Monitor for a Battery Stack

10,000

10

0 20 3010 100

100

1000

MAX4040-44 fig07

V

OD

(mV)

t

PD

(µs)

40 50 60 70 80

90

tPD-; V

CC

= +5V

tPD+; V

CC

= +2.4V

tPD-; V

CC

= +2.4V

tPD+; V

CC

= +5V

Figure 7. Propagation Delay vs. Input Overdrive

MAX4040–MAX4044

Single/Dual/Quad, Low-Cost, SOT23,

Micropower, Rail-to-Rail I/O Op Amps

______________________________________________________________________________________ 13

_____________________________________________Pin Configurations (continued)

OUT

N.C.V

EE

1
2

87N.C.

V

CC

IN-

IN+

N.C.

SO/µMAX

TOP VIEW

3

4

6

5

MAX4040

OUT

N.C.V

EE

1
2

87SHDN

VCCIN-

IN+

N.C.

SO/µMAX

3

4

6

5

MAX4041

INB-

INB+V

EE

1
2

87V

CC

OUTBINA-

INA+

OUTA

SO/µMAX

3

4

6

5

MAX4042

14
13
12
11
10

9
8

1
2
3
4
5
6
7

V

CC

OUTB
INB­INB+V

EE

INA+

INA-

OUTA

MAX4043

N.C.
SHDNB
N.C.N.C.

SHDNA

N.C.

SO

14
13
12
11
10

9
8

1
2
3
4
5
6
7

OUTD
IND­IND+
V

EE

V

CC

INA+

INA-

OUTA

MAX4044

INC+
INC­OUTCOUTB

INB-

INB+

SO

1
2
3
4
5

10

9
8
7
6

V

CC

OUTB
INB­INB+V

EE

INA+

INA-

OUTA

MAX4043

µMAX

SHDNBSHDNA

MAX4040/MAX4041

TRANSISTOR COUNT: 234

MAX4042/MAX4043

TRANSISTOR COUNT: 466

MAX4044

TRANSISTOR COUNT: 932
SUBSTRATE CONNECTED TO V

EE

___________________Chip Information

MAX4040–MAX4044

Single/Dual/Quad, Low-Cost, SOT23,
Micropower, Rail-to-Rail I/O Op Amps

14 ______________________________________________________________________________________

________________________________________________________Package Information

SOT5L.EPS

MAX4040–MAX4044

Single/Dual/Quad, Low-Cost, SOT23,

Micropower, Rail-to-Rail I/O Op Amps

______________________________________________________________________________________ 15

___________________________________________Package Information (continued)

8LUMAXD.EPS

MAX4040–MAX4044

Single/Dual/Quad, Low-Cost, SOT23,
Micropower, 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.

16

____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

© 1998 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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.

16

____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

© 1998 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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.

16

____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

© 1998 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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.

16

____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

© 1998 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

Package Information (continued)

10LUMAXB.EPS