MAX4080SASA-T - Maxim Integrated

Selector Guide appears at end of data sheet.

µMAX is a registered trademark of Maxim Integrated Products, Inc.

Ordering Information continued at end of data sheet.

General Description

The MAX4080/MAX4081 are high-side, current-sense

amplifiers with an input voltage range that extends from

4.5V to 76V making them ideal for telecom, automotive,

backplane, and other systems where high-voltage current

monitoring is critical. The MAX4080 is designed for uni-

directional current-sense applications and the MAX4081

allows bidirectional current sensing. The MAX4081 sin-

gle output pin continuously monitors the transition from

charge to discharge and avoids the need for a separate

polarity output. The MAX4081 requires an external refer-

ence to set the zero-current output level (VSENSE = 0V).

The charging current is represented by an output voltage

from VREF to VCC, while discharge current is given from

VREF to GND.

For maximum versatility, the 76V input voltage range

applies independently to both supply voltage (VCC) and

common-mode input voltage (VRS+). High-side current

monitoring does not interfere with the ground path of the

load being measured, making the MAX4080/MAX4081

particularly useful in a wide range of high-voltage sys-

tems.

The combination of three gain versions (5V/V, 20V/V,

60V/V = F, T, S suffix) and a user-selectable, external

sense resistor sets the full-scale current reading and its

proportional output voltage. The MAX4080/MAX4081

offer a high level of integration, resulting in a simple, accu-

rate, and compact current-sense solution.

The MAX4080/MAX4081 operate from a 4.5V to 76V sin-

gle supply and draw only 75µA of supply current. These

devices are specified over the automotive operating tem-

perature range (-40°C to +125°C) and are available in a

space-saving 8-pin µMAX® or SO package.

Applications

●Automotive (12V, 24V, or 42V Batteries)

●48V Telecom and Backplane Current Measurement

●Bidirectional Motor Control

●Power-Management Systems

●Avalanche Photodiode and PIN-Diode Current

Monitoring

●General System/Board-Level Current Sensing

●Precision High-Voltage Current Sources

Benets and Features

●Ideal for High-Voltage Current Monitoring Applications

• Wide 4.5V to 76V Input Common-Mode Range

• Independent Operating Supply Voltage

●High Accuracy and Low Quiescent Current Support

Precision Application Requirements

• ±0.1% Full-Scale Accuracy

• Low 100μV Input Offset Voltage

• Three Gain Versions Available

- 5V/V (MAX4080F/MAX4081F)

- 20V/V (MAX4080T/MAX4081T)

- 60V/V (MAX4080S/MAX4081S)

• 75μA Supply Current (MAX4080)

●Flexible Current Sensing Supports Monitoring of

Charge and Discharge of Batteries

• Bidirectional (MAX4081) or Unidirectional

(MAX4080) ISENSE

• Reference Input for Bidirectional OUT (MAX4081)

●Minimizes Required Board Space

• 8-Pin μMAX Package

+Denotes a lead(Pb)-free/RoHS-compliant package.

/V denotes an automotive qualified part.

PART TEMP RANGE PIN-PACKAGE

MAX4080FAUA+ -40°C to +125°C 8 µMAX

MAX4080FAUA/V+ -40°C to +125°C 8 µMAX

MAX4080FASA+ -40°C to +125°C 8 SO

MAX4080TAUA+ -40°C to +125°C 8 µMAX

MAX4080TAUA/V+ -40°C to +125°C 8 µMAX

N.C.

OUTGND

RS-

N.C.VCC

N.C.

RS+

µMAX/SO

TOP VIEW

MAX4080

REF1B

OUTGND

RS-

REF1AVCC

N.C.

RS+

µMAX/SO

MAX4081

MAX4080/MAX4081 76V, High-Side, Current-Sense Ampliers

with Voltage Output

19-2562; Rev 5; 5/15

Pin Congurations

Ordering Information

EVALUATION KIT AVAILABLE

VCC to GND ..........................................................-0.3V to +80V

RS+, RS- to GND ..................................................-0.3V to +80V

OUT to GND .......... -0.3V to the lesser of +18V or (VCC + 0.3V)

REF1A, REF1B to GND

(MAX4081 Only) -0.3V to the lesser of +18V or (VCC + 0.3V)

Output Short Circuit to GND......................................Continuous

Differential Input Voltage (VRS+ - VRS-) .............................. ±80V

Current into Any Pin .........................................................±20mA

Continuous Power Dissipation (TA = +70°C)

8-Pin ?MAX (derate 4.5mW/°C above +70°C) ............362mW

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

Operating Temperature Range ......................... -40°C to +125°C

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

Storage Temperature Range ............................ -65°C to +150°C

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

Soldering Temperature (reflow) ....................................... +260°C

(VCC = VRS+ = 4.5V to 76V, VREF1A = VREF1B = 5V (MAX4081 only), VSENSE = (VRS+ - VRS-) = 0V, RLOAD = 100kΩ, TA = TMIN to

TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Notes 1, 2)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Operating Voltage Range VCC Inferred from PSRR test 4.5 76 V

Common-Mode Range CMVR Inferred from CMRR test (Note 3) 4.5 76 V

Supply Current ICC VCC = VRS+ = 76V,

no load

MAX4080 75 190 µA

MAX4081 103 190

Leakage Current IRS+, IRS- VCC = 0V, VRS+ = 76V 0.01 2 µA

Input Bias Current IRS+, IRS- VCC = VRS+ = 76V 5 12 µA

Full-Scale Sense Voltage

(Note 4) VSENSE

MAX4080F/MAX4081F ±1000

mVMAX4080T/MAX4081T ±250

MAX4080S/MAX4081S ±100

Gain AV

MAX4080F/MAX4081F 5

V/VMAX4080T/MAX4081T 20

MAX4080S/MAX4081S 60

Gain Accuracy DAV

VCC = VRS+ = 48V

(Note 5)

TA = +25°C±0.1 ±0.6

%TA = -40°C to +85°C±1

TA = TMIN to TMAX ±1.2

Input Offset Voltage VOS

VCC = VRS+ = 48V

(Note 6)

TA = +25°C ±0.1 ±0.6

mVTA = -40°C to +85°C±1

TA = TMIN to TMAX ±1.2

Common-Mode Rejection Ratio

(Note 7) CMRR VCC = 48V, VRS+ = 4.5V to 76V 100 124 dB

Power-Supply Rejection Ratio

(Note 7) PSRR VRS+ = 48V, VCC = 4.5V to 76V 100 122 dB

OUT High Voltage (VCC –

VOH)

VCC = 4.5V, VRS+

= 48V, VREF1A =

VREF1B = 2.5V,

IOUT (sourcing) =

+500µA (Note 8)

MAX4080F/MAX4081F,

VSENSE = 1000mV

0.15 0.27 V

MAX4080T/MAX4081T,

VSENSE = 250mV

MAX4080S/MAX4081S,

VSENSE = 100mV

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MAX4080/MAX4081 76V, High-Side, Current-Sense Ampliers

with Voltage Output

DC Electrical Characteristics

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.

Absolute Maximum Ratings

(VCC = VRS+ = 4.5V to 76V, VREF1A = VREF1B = 5V (MAX4081 only), VSENSE = (VRS+ - VRS-) = 0V, RLOAD = 100kΩ, TA = TMIN to

TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Notes 1, 2)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

OUT Low Voltage VOL

VCC = VRS+ = 48V,

VREF1A = VREF1B =

2.5V, VSENSE =

-1000mV (for

MAX4081 only)

IOUT (sinking) = 10µA 4 15

IOUT (sinking) = 100µA 23 55

REF1A = REF1B Input Voltage

Range (MAX4081 Only)

(VREF –

VGND)

Inferred from REF1A rejection ratio,

VREF1A = VREF1B 1.5 6 V

REF1A Input Voltage Range

(MAX4081 Only)

(VREF1A –

VGND)

Inferred from REF1A rejection ratio,

VREF1B = VGND 3 12 V

REF1A Rejection Ratio

(MAX4081 Only)

VCC = VRS+ = 48V, VSENSE = 0V,

VREF1A = VREF1B = 1.5V to 6V 80 108 dB

REF/REF1A Ratio

(MAX4081 Only)

VREF1A = 10V, VREF1B = VGND,

VCC = VRS+ = 48V (Note 2) 0.497 0.500 0.503

REF1A Input Impedance

(MAX4081 Only) VREF1B = VGND 250 kΩ

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MAX4080/MAX4081 76V, High-Side, Current-Sense Ampliers

with Voltage Output

DC Electrical Characteristics (continued)

Note 1: All devices are 100% production tested at TA = +25°C. All temperature limits are guaranteed by design.

Note 2: VREF is defined as the average voltage of VREF1A and VREF1B. REF1B is usually connected to REF1A or GND.

VSENSE is defined as VRS+ - VRS-.

Note 3: The common-mode range at the low end of 4.5V applies to the most positive potential at RS+ or RS-. Depending on the

polarity of VSENSE and the device’s gain, either RS+ or RS- can extend below 4.5V by the device’s typical full-scale value of

VSENSE.

Note 4: Negative VSENSE applies to MAX4081 only.

Note 5: VSENSE is:

MAX4080F, 10mV to 1000mV

MAX4080T, 10mV to 250mV

MAX4080S, 10mV to 100mV

MAX4081F, -500mV to +500mV

MAX4081T, -125mV to +125mV

MAX4081S, -50mV to +50mV

Note 6: VOS is extrapolated from the gain accuracy test for the MAX4080 and measured as (VOUT - VREF)/AV at VSENSE = 0V, for

the MAX4081.

Note 7: VSENSE is:

MAX4080F, 500mV

MAX4080T, 125mV

MAX4080S, 50mV

MAX4081F/T/S, 0V

VREF1B = VREF1A = 2.5V

Note 8: Output voltage is internally clamped not to exceed 18V.

Note 9: Output settles to within 1% of final value.

Note 10: The device will not experience phase reversal when overdriven.

(VCC = VRS+ = 4.5V to 76V, VREF1A = VREF1B = 5V (MAX4081 only), VSENSE = (VRS+ - VRS-) = 0V, RLOAD = 100kΩ, CLOAD = 20pF,

TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Notes 1, 2)

PARAMETER SYMBOL CONDITION MIN TYP MAX UNITS

Bandwidth BW VCC = VRS+ = 48V,

VOUT = 2.5V

MAX4080F/T/S 250 kHz

MAX4081F/T/S 150

OUT Settling Time to 1% of Final

Value

VSENSE = 10mV to 100mV 20 µs

VSENSE = 100mV to 10mV 20

Capacitive-Load Stability No sustained oscillations 500 pF

Output Resistance ROUT VSENSE = 100mV 0.1 Ω

Power-Up Time VCC = VRS+ = 48V, VSENSE = 100mV (Note 9) 50 µs

Saturation Recovery Time (Notes 9,10) 50 µs

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MAX4080/MAX4081 76V, High-Side, Current-Sense Ampliers

with Voltage Output

AC Electrical Characteristics

(VCC = VRS+ = 48V, VSENSE = 0V, CLOAD = 20pF, RLOAD = ∞, TA = +25°C, unless otherwise noted.)

MAX4080 toc09

FREQUENCY (kHz)

GAIN (dB)

100101

0.1 1000

MAX4081F/T/S

SMALL-SIGNAL GAIN vs. FREQUENCY

VOUT = 100mVP-P

MAX4081S

MAX4081T

MAX4081F

MAX4080 toc08

FREQUENCY (kHz)

GAIN (dB)

100101

0.1 1000

MAX4080F/T/S

SMALL-SIGNAL GAIN vs. FREQUENCY

VSENSE = 10mV

MAX4080S

MAX4080T

MAX4080F

MAX4080 toc07

FREQUENCY (Hz)

REFERENCE REJECTION RATIO (dB)

-110

-90

-100

-80

-60

-70

-50

-40

-20

-30

-10

-120

MAX4081F/T/S

REFERENCE REJECTION RATIO

vs. FREQUENCY

10k1k100101 100k

MAX4080 toc06

FREQUENCY (Hz)

POWER-SUPPLY REJECTION RATIO (dB)

100k10k1k10010

-120

-100

-110

-90

-80

-60

-70

-50

-40

-20

-30

-10

-130

1 1M

MAX4081F/T/S

POWER-SUPPLY REJECTION RATIO

vs. FREQUENCY

MAX4080 toc05

FREQUENCY (Hz)

COMMON-MODE REJECTION RATIO (dB)

100k10k1k10010

-120

-100

-110

-90

-80

-60

-70

-50

-40

-20

-30

-10

-130

1 1M

MAX4081F/T/S

COMMON-MODE REJECTION RATIO

vs. FREQUENCY

GAIN ACCURACY vs. VCC

MAX4080 toc04

VCC (V)

GAIN ACCURACY (%)

6452402816

-0.15

-0.10

-0.05

-0.20

4 76

VRS+ = 48V

S VERSION

T VERSION

F VERSION

-0.5

-0.2

-0.3

-0.4

-0.1

0.4

0.3

0.2

0.1

0.5

-50 -25 0 25 50 75 100 125

GAIN ACCURACY vs. TEMPERATURE

MAX4080 toc03

TEMPERATURE (°C)

GAIN ACCURACY (%)

INPUT OFFSET VOLTAGE

vs. TEMPERATURE

MAX4080 toc02

-300

-250

-150

-200

-50

-100

300

100

150

200

250

INPUT OFFSET VOLTAGE (V)

-50 25 500-25 75 100 125 150

TEMPERATURE (°C)

-125 -75 -50 -25-100 0 25 50 75 100 125

INPUT OFFSET VOLTAGE HISTOGRAM

MAX4080 toc01

INPUT OFFSET VOLTAGE (µV)

PERCENTAGE (%)

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MAX4080/MAX4081 76V, High-Side, Current-Sense Ampliers

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Typical Operating Characteristics

(VCC = VRS+ = 48V, VSENSE = 0V, CLOAD = 20pF, RLOAD = ∞, TA = +25°C, unless otherwise noted.)

MAX4080 toc18

INPUT

5mV/div

OUTPUT

300mV/div

20µs/div

MAX4080S

SMALL-SIGNAL TRANSIENT RESPONSE

MAX4080 toc17

INPUT

5mV/div

OUTPUT

100mV/div

20µs/div

MAX4080T

SMALL-SIGNAL TRANSIENT RESPONSE

MAX4080 toc16

INPUT

5mV/div

OUTPUT

25mV/div

20µs/div

MAX4080F

SMALL-SIGNAL TRANSIENT RESPONSE

45040035030025020015010050

100

150

200

250

300

0 500

VOUT LOW VOLTAGE

vs. IOUT (SINKING)

MAX4080 toc15

IOUT (SINKING) (µA)

VOUT LOW VOLTAGE (mV)

TA = +125°C

TA = +85°C

TA = +25°C

TA = 0°C

TA = -40°C

VCC = 4.5V

MAX4080 toc14

IOUT (SOURCING) (mA)

VOUT HIGH VOLTAGE (VCC - VOH) (V)

0.90.80.6 0.70.2 0.3 0.4 0.50.1

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

0 1.0

VOUT HIGH VOLTAGE

vs. IOUT (SOURCING)

VCC = 4.5V

TA = +125°C

TA = +85°C

TA = +25°C

TA = 0

TA = -40°C

110

105

100

115

-50 -25 0 25 50 75 100 125

MAX4081

SUPPLY CURRENT vs. TEMPERATURE

MAX4080 toc13

TEMPERATURE (°C)

SUPPLY CURRENT (µA)

VREF1A = VREF1B = 2.5V

110

105

100

115

-50 -25 0 25 50 75 100 125

MAX4080

SUPPLY CURRENT vs. TEMPERATURE

MAX4080 toc12

TEMPERATURE (°C)

SUPPLY CURRENT (µA)

MAX4080 toc11

VCC (V)

SUPPLY CURRENT (µA)

645216 28 40

100

105

110

115

120

125

4 76

MAX4081

SUPPLY CURRENT vs. VCC

VREF = 2.5V

NO LOAD

VSENSE = 0V

4 2816 40 52 64 76

MAX4080

SUPPLY CURRENT vs. VCC

MAX4080 toc10

VCC (V)

SUPPLY CURRENT (µA)

NO LOAD

VSENSE = 0V

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MAX4080/MAX4081 76V, High-Side, Current-Sense Ampliers

with Voltage Output

Typical Operating Characteristics (continued)

(VCC = VRS+ = 48V, VSENSE = 0V, CLOAD = 20pF, RLOAD = ∞, TA = +25°C, unless otherwise noted.)

MAX4080 toc27

INPUT

33mV/div

OUTPUT

2V/div

20µs/div

MAX4081S

LARGE-SIGNAL TRANSIENT RESPONSE

MAX4080 toc26

INPUT

100mV/div

OUTPUT

2V/div

20µs/div

MAX4081T

LARGE-SIGNAL TRANSIENT RESPONSE

MAX4080 toc25

INPUT

400mV/div

OUTPUT

2V/div

20µs/div

MAX4081F

LARGE-SIGNAL TRANSIENT RESPONSE

MAX4080 toc24

INPUT

33mV/div

OUTPUT

2V/div

20µs/div

MAX4080S

LARGE-SIGNAL TRANSIENT RESPONSE

MAX4080 toc23

INPUT

100mV/div

OUTPUT

2V/div

20µs/div

MAX4080T

LARGE-SIGNAL TRANSIENT RESPONSE

MAX4080 toc22

INPUT

400mV/div

OUTPUT

2V/div

20µs/div

MAX4080F

LARGE-SIGNAL TRANSIENT RESPONSE

MAX4080 toc21

INPUT

1mV/div

OUTPUT

50mV/div

20µs/div

MAX4081S

SMALL-SIGNAL TRANSIENT RESPONSE

MAX4080 toc20

INPUT

2.5mV/div

OUTPUT

50mV/div

20µs/div

MAX4081T

SMALL-SIGNAL TRANSIENT RESPONSE

MAX4080 toc19

INPUT

10mV/div

OUTPUT

50mV/div

20µs/div

MAX4081F

SMALL-SIGNAL TRANSIENT RESPONSE

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MAX4080/MAX4081 76V, High-Side, Current-Sense Ampliers

with Voltage Output

Typical Operating Characteristics (continued)

(VCC = VRS+ = 48V, VSENSE = 0V, CLOAD = 20pF, RLOAD = ∞, TA = +25°C, unless otherwise noted.)

MAX4080 toc30

VCC

(0 TO 10V)

5V/div

OUTPUT

2.5V/div

100µs/div

MAX4080T

STARTUP DELAY

(VSENSE = 250mV)

MAX4080 toc29

INPUT

500mV/div

OUTPUT

2V/div

20µs/div

MAX4080F

SATURATION RECOVERY RESPONSE

(VCC = 4.5V)

MAX4080 toc28

4µs/div

VCC-TRANSIENT RESPONSE

VCC

5V/div

VOUT

1V/div

VRS+ = 20V

VCC = 20V STEP

VREF1 = VREF2 = 2.5V

VCC = 40V

VCC = 20V

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MAX4080/MAX4081 76V, High-Side, Current-Sense Ampliers

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Typical Operating Characteristics (continued)

Detailed Description

The MAX4080/MAX4081 unidirectional and bidirectional

high-side, current-sense amplifiers feature a 4.5V to 76V

input common-mode range that is independent of supply

voltage. This feature allows the monitoring of current out

of a battery as low as 4.5V and also enables high-side cur-

rent sensing at voltages greater than the supply voltage

(VCC). The MAX4080/MAX4081 monitors current through

a current-sense resistor and amplifies the voltage across

the resistor. The MAX4080 senses current unidirectional-

ly, while the MAX4081 senses current bidirectionally.

The 76V input voltage range of the MAX4080/MAX4081

applies independently to both supply voltage (VCC) and

common-mode, input-sense voltage (VRS+). High-side

current monitoring does not interfere with the ground

path of the load being measured, making the MAX4080/

MAX4081 particularly useful in a wide range of high-volt-

age systems.

Battery-powered systems require a precise bidirectional

current-sense amplifier to accurately monitor the battery’s

charge and discharge. The MAX4081 charging current

is represented by an output voltage from VREF to VCC,

while discharge current is given from VREF to GND.

Measurements of OUT with respect to VREF yield a posi-

tive and negative voltage during charge and discharge, as

illustrated in Figure 1 for the MAX4081T.

Current Monitoring

The MAX4080 operates as follows: current from the

source flows through RSENSE to the load (Figure 2), cre-

ating a sense voltage, VSENSE. Since the internal-sense

amplifier’s inverting input has high impedance, negligible

current flows through RG2 (neglecting the input bias

current). Therefore, the sense amplifier’s inverting input

voltage equals VSOURCE - (ILOAD)(RSENSE). The ampli-

fier’s open-loop gain forces its noninverting input to the

same voltage as the inverting input. Therefore, the drop

across RG1 equals VSENSE. The internal current mirror

multiplies IRG1 by a current gain factor, β, to give IA2 =

β × IRG1. Amplifier A2 is used to convert the output

current to a voltage and then sent through amplifier

A3. Total gain = 5V/V for MAX4080F, 20V/V for the

MAX4080T, and 60V/V for the MAX4080S.

The MAX4081 input stage differs slightly from the

MAX4080 (Figure 3). Its topology allows for monitoring

of bidirectional currents through the sense resistor. When

current flows from RS+ to RS-, the MAX4081 matches the

voltage drop across the external sense resistor, RSENSE,

by increasing the current through the Q1 and RG1. In this

way, the voltages at the input terminals of the internal

amplifier A1 are kept constant and an accurate measure-

ment of the sense voltage is achieved. In the following

amplifier stages of the MAX4081, the output signal of

amplifier A2 is level- shifted to the reference voltage

(VREF = VREF1A = VREF1B), resulting in a voltage at the

output pin (OUT)

PIN NAME FUNCTION

MAX4080 MAX4081

1 1 RS+ Power connection to the external-sense resistor.

2 2 VCC Supply Voltage Input. Decouple VCC to GND with at least a 0.1µF capacitor to

bypass line transients.

3, 6, 7 3 N.C. No Connection. No internal connection. Leave open or connect to ground.

4 4 GND Ground

5 5 OUT

Voltage Output. For the unidirectional MAX4080, VOUT is proportional to

VSENSE. For the bidirectional MAX4081, the difference voltage (VOUT - VREF) is

proportional to VSENSE and indicates the correct polarity.

8 8 RS- Load connection to the external sense resistor.

— 6 REF1B Reference Voltage Input: Connect REF1B to REF1A or to GND (see the External

Reference section).

— 7 REF1A

Reference Voltage Input: Connect REF1A and REF1B to a fixed reference

voltage (VREF). VOUT is equal to VREF when VSENSE is zero (see the External

Reference section).

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MAX4080/MAX4081 76V, High-Side, Current-Sense Ampliers

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Pin Description

that swings above VREF voltage for positive-sense volt-

ages and below VREF for negative-sense voltages.

VOUT is equal to VREF when VSENSE is equal to zero.

Set the full-scale output range by selecting RSENSE

and the appropriate gain version of the MAX4080/

MAX4081.

Note: For Gain = 5 (F), RG1 = RG2 = 160k.

For Gain = 20 (T), RG1 = RG2 = 60k.

For Gain = 60 (S), RG1 = RG2 = 20k.

Figure 3. MAX4081 Functional DiagramFigure 2. MAX4080 Functional Diagram

Figure 1. MAX4081T OUT Transfer Curve

VSENSE

RG1 RG2

VREF

RS-

REF1B

OUT

GND

REF1A

Q1 Q2

125kΩ

RS+

CURRENT

MIRROR

CURRENT

MIRROR

MAX4081

RSENSE

VSENSE

ILOAD

OUT

RG1 RG2

RS-

RS+

CURRENT

MIRROR

IA2

A3A2

MAX4080

MAX4081T

VSENSE ICHARGE

ILOAD

RSENSE

VCC

GND

RS+RS-

OUT

REF1A

REF1B

SYSTEM LOAD

AND CHARGER

BATTERY

VOUT = VGND

VOUT = 10V

VREF1A = VREF1B = 5V

DISCHARGE CURRENT

4.5V TO 76V

VOUT - VREF

CHARGE CURRENT

10V

-250mV 250mV

-5V

VSENSE

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MAX4080/MAX4081 76V, High-Side, Current-Sense Ampliers

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External References (MAX4081)

For the bidirectional MAX4081, the VOUT reference level

is controlled by REF1A and REF1B. VREF is defined as

the average voltage of VREF1A and VREF1B. Connect

REF1A and REF1B to a low-noise, regulated voltage

source to set the output reference level. In this mode,

VOUT equals VREF1A when VSENSE equals zero (see

Figure 4).

Alternatively, connect REF1B to ground, and REF1A to a

low-noise, regulated voltage source. In this case, the out-

put reference level (VREF) is equal to VREF1A divided by

two. VOUT equals VREF1A/2 when VSENSE equals zero.

In either mode, the output swings above the reference

voltage for positive current-sensing (VRS+ > VRS-). The

output swings below the reference voltage for negative

current-sensing (VRS+ < VRS-).

Applications Information

Recommended Component Values

Ideally, the maximum load current develops the full-scale

sense voltage across the current-sense resistor. Choose

the gain needed to yield the maximum output voltage

required for the application:

VOUT = VSENSE 5 AV

where VSENSE is the full-scale sense voltage, 1000mV

for gain of 5V/V, 250mV for gain of 20V/V, 100mV for gain

of 60V/V, and AV is the gain of the device.

In applications monitoring a high current, ensure that

RSENSE is able to dissipate its own I2R loss. If the resis-

tor’s power dissipation is exceeded, its value may drift or

it may fail altogether.

The MAX4080/MAX4081 sense a wide variety of currents

with different sense-resistor values. Table 1 lists common

resistor values for typical operation.

Table 1. Typical Component Values

FULL-SCALE LOAD

CURRENT, ILOAD (A)

CURRENT-SENSE

RESISTOR (mΩ)

GAIN

(V/V)

FULL-SCALE

VSENSE

(mV)

MAX4081 FULL-SCALE

OUTPUT VOLTAGE

(VOUT - VREF, V)

0.500 1000 5 ±500 ±2.5

0.125 1000 20 ±125 ±2.5

0.050 1000 60 ±50 ±3.0

5.000 100 5 ±500 ±2.5

1.250 100 20 ±125 ±2.5

0.500 100 60 ±50 ±3.0

50.000 10 5 ±500 ±2.5

12.500 10 20 ±125 ±2.5

5.000 10 60 ±50 ±3.0

FULL-SCALE LOAD

CURRENT, ILOAD (A)

CURRENT-SENSE

RESISTOR (mΩ)

GAIN

(V/V)

FULL-SCALE

VSENSE

(mV)

MAX4080 FULL-SCALE

OUTPUT VOLTAGE (V)

1.000 1000 5 1000 5.0

0.250 1000 20 250 5.0

0.100 1000 60 100 6.0

10.000 100 5 1000 5.0

2.500 100 20 250 5.0

1.000 100 60 100 6.0

50.000 10 5 500 2.5

25.000 10 20 250 5.0

10.000 10 60 100 6.0

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MAX4080/MAX4081 76V, High-Side, Current-Sense Ampliers

with Voltage Output

The full-scale output voltage is VOUT = RSENSE × ILOAD

(MAX) × AV, for the MAX4080 and VOUT = VREF ± RSENSE

× ILOAD(MAX) × AV for the MAX4081. VSENSE(MAX) is

1000mV for the 5V/V gain version, 250mV for the 20V/V

gain version, and 100mV for the 60V/V gain version.

Choosing the Sense Resistor

Choose RSENSE based on the following criteria:

Voltage Loss: A high RSENSE value causes the pow-

er-source voltage to degrade through IR loss. For minimal

voltage loss, use the lowest RSENSE value.

●Accuracy: A high RSENSE value allows lower cur-

rents to be measured more accurately. This is due

to offsets becoming less significant when the sense

voltage is larger. For best performance, select

RSENSE to provide approximately 1000mV (gain of

5V/V), 250mV (gain of 20V/V), or 100mV (gain of

60V/V) of sense voltage for the full-scale current in

each application.

●Efficiency and Power Dissipation: At high current

levels, the I2R losses in RSENSE can be significant.

Take this into consideration when choosing the resis-

tor value and its power dissipation (wattage) rating.

Also, the sense resistor’s value might drift if it is

allowed to heat up excessively.

●Inductance: Keep inductance low if ISENSE has a

large high-frequency component. Wire-wound resis-

tors have the highest inductance, while metal film is

somewhat better. Low-inductance, metal-film resistors

are also available. Instead of being spiral- wrapped

around a core, as in metal-film or wire-wound resis-

tors, they are a straight band of metal and are avail-

able in values under 1Ω.

Because of the high currents that flow through RSENSE,

take care to eliminate parasitic trace resistance from

causing errors in the sense voltage. Either use a four-ter-

minal current-sense resistor or use Kelvin (force and

sense) PC board layout techniques.

Dynamic Range Consideration

Although the MAX4081 have fully symmetrical bidirec-

tional VSENSE input capability, the output voltage range

is usually higher from REF to VCC and lower from REF

to GND (unless the supply voltage is at the lowest end of

the operating range). Therefore, the user must consider

the dynamic range of current monitored in both directions

and choose the supply voltage and the reference voltage

(REF) to make sure the output swing above and below

REF is adequate to handle the swings without clipping or

running out of headroom.

Power-Supply Bypassing and Grounding

For most applications, bypass VCC to GND with a 0.1µF

ceramic capacitor. In many applications, VCC can be

connected to one of the current monitor terminals (RS+

or RS-). Because VCC is independent of the monitored

voltage, VCC can be connected to a separate regulated

supply.

If VCC will be subject to fast-line transients, a series

resistor can be added to the power-supply line of the

MAX4080/MAX4081 to minimize output disturbance. This

resistance and the decoupling capacitor reduce the rise

time of the transient. For most applications, 1kΩ in con-

junction with a 0.1µF bypass capacitor work well.

The MAX4080/MAX4081 require no special consider-

ations with respect to layout or grounding. Consideration

should be given to minimizing errors due to the large

charge and discharge currents in the system.

Figure 4. MAX4081 Reference Inputs

MAX4081

RSENSE

ILOAD = 0

LOAD

VCC

GND

RS-RS+

OUT

REF1A

REF1B

10V

MAX4081

RSENSE

ILOAD = 0

LOAD

VCC

GND

RS-RS+

OUT

REF1A

REF1B

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MAX4080/MAX4081 76V, High-Side, Current-Sense Ampliers

with Voltage Output

Power Management

The bidirectional capability of the MAX4081 makes it an

excellent candidate for use in smart battery packs. In the

application diagram (Figure 5), the MAX4081 monitors the

charging current into the battery as well as the discharge

current out of the battery. The microcontroller stores this

information, allowing the system to query the battery’s

status as needed to make system power-management

decisions.

+Denotes a lead(Pb)-free/RoHS-compliant package.

Figure 5. MAX4081 Used In Smart-Battery Application

PACKAGE

TYPE

PACKAGE

CODE

OUTLINE

NO.

LAND

PATTERN NO.

8 µMAX U8+1 21-0036 90-0092

8 SO S8+2 21-0041 90-0096

PART TEMP RANGE PIN-PACKAGE

MAX4080TASA+ -40°C to +125°C 8 SO

MAX4080SAUA+ -40°C to +125°C 8 µMAX

MAX4080SAUA/V+ -40°C to +125°C 8 µMAX

MAX4080SASA+ -40°C to +125°C 8 SO

MAX4081FAUA+ -40°C to +125°C 8 µMAX

MAX4081FASA+ -40°C to +125°C 8 SO

MAX4081TAUA+ -40°C to +125°C 8 µMAX

MAX4081TASA+ -40°C to +125°C 8 SO

MAX4081SAUA+ -40°C to +125°C 8 µMAX

MAX4081SASA+ -40°C to +125°C 8 SO

PART GAIN (V/V) ISENSE

MAX4080FAUA 5 Unidirectional

MAX4080FASA 5 Unidirectional

MAX4080TAUA 20 Unidirectional

MAX4080TASA 20 Unidirectional

MAX4080SAUA 60 Unidirectional

MAX4080SASA 60 Unidirectional

MAX4081FAUA 5 Bidirectional

MAX4081FASA 5 Bidirectional

MAX4081TAUA 20 Bidirectional

MAX4081TASA 20 Bidirectional

MAX4081SAUA 60 Bidirectional

MAX4081SASA 60 Bidirectional

MAX4080

VCC = 4.5V TO 76V

RSENSE

ISENSE

SYSTEM

LOAD

VCC

GND

RS-RS+

OUT

MAX4081

RSENSE

VCC

GND

RS-RS+

OUT

REF1A

REF1B

SYSTEM

POWER

MANAGEMENT

AND

CHARGER

CIRCUITRY

µC

1.8V

SERIAL

INTERFACE

BATTERY

MAX1243

ADC

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MAX4080/MAX4081 76V, High-Side, Current-Sense Ampliers

with Voltage Output

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.

Ordering Information (continued)

Chip Information

PROCESS: Bipolar

Typical Operating Circuit

Selector Guide

REVISION

NUMBER

REVISION

DATE DESCRIPTION PAGES

CHANGED

0 10/02 Initial release —

1 11/08 Added values for RG1 and RG2 10

2 5/09 Added lead-free and automotive parts to Ordering Information 1

3 5/10 Removed automotive part and added soldering temperature 1, 2

4 7/11 Added automotive part designation 1

5 5/15 Updated Benefits and Features section 1

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 specications 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.

│

MAX4080/MAX4081 76V, High-Side, Current-Sense Ampliers

with Voltage Output

Revision History

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.