MAXIM MAX4080, MAX4081 Technical data

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 unidirectional current-sense applications and the MAX4081 allows bidirectional current sensing. The MAX4081 single output pin continuously monitors the transition from charge to discharge and avoids the need for a separate polarity output. The MAX4081 requires an external reference to set the zero-current output level (V

SENSE

= 0V). The charging current is rep-

resented by an output voltage from V

REF

to VCC, while

discharge current is given from V

REF

to GND.

For maximum versatility, the 76V input voltage range applies independently to both supply voltage (V

)

and common-mode input voltage (V

RS+

). 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 systems.

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, accurate, and compact current-sense solution.

The MAX4080/MAX4081 operate from a 4.5V to 76V single supply and draw only 75µA of supply current. These devices are specified over the automotive operating temperature 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

Features

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

♦ Bidirectional or Unidirectional I

SENSE

♦ Low-Cost, Compact, Current-Sense Solution

♦ Three Gain Versions Available

5V/V (MAX4080F/MAX4081F) 20V/V (MAX4080T/MAX4081T) 60V/V (MAX4080S/MAX4081S)

♦ ±0.1% Full-Scale Accuracy

♦ Low 100µV Input Offset Voltage

♦ Independent Operating Supply Voltage

♦ 75µA Supply Current (MAX4080)

♦ Reference Input for Bidirectional OUT (MAX4081)

♦ Available in a Space-Saving 8-Pin µMAX Package

MAX4080/MAX4081

76V, High-Side, Current-Sense Amplifiers with

Voltage Output

________________________________________________________________ Maxim Integrated Products 1

Pin Configurations

Ordering Information

19-2562; Rev 0; 10/02

For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

EVALUATION KIT

AVAILABLE

Selector Guide appears at end of data sheet.

PART TEMP RANGE PIN-PACKAGE

MAX4080FAUA -40°C to +125°C 8 µMAX

MAX4080FASA -40°C to +125°C 8 SO

MAX4080TAUA -40°C to +125°C 8 µMAX

MAX4080TASA -40°C to +125°C 8 SO

MAX4080SAUA -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

TOP VIEW

RS+

N.C.

MAX4080

87RS-

N.C.V

N.C.

OUTGND

RS+

N.C.

MAX4081

87RS-

REF1AV

REF1B

OUTGND

μMAX/SO

MAX4080/MAX4081

76V, High-Side, Current-Sense Amplifiers with Voltage Output

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

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.

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

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

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

+ 0.3V)

REF1A, REF1B to GND

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

+ 0.3V)

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

Differential Input Voltage (V

+ - VRS-)...............................±80V

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

Continuous Power Dissipation (T

= +70°C)

8-Pin µMAX (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

DC ELECTRICAL CHARACTERISTICS

(VCC= V

RS+

= 4.5V to 76V, V

REF1A

= V

REF1B

= 5V (MAX4081 only), V

SENSE

= (V

RS+

- V

RS-

) = 0V, R

LOAD

= 100kΩ, TA= T

MIN

MAX

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

Operating Voltage Range V

Common-Mode Range C

Supply Current I

Leakage Current I

Input Bias Current I

Full-Scale Sense Voltage (Note 4) V

Input Offset Voltage V

Common-Mode Rejection Ratio

Power-Supply Rejection Ratio

OUT High Voltage

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

MVR

RS+

Inferred from PSRR test 4.5 76 V

Inferred from CMRR test (Note 3) 4.5 76 V

MAX4080 75 190

MAX4081 103 190

= 76V 0.01 2 µA

, I

RS-VCC

, I

RS-VCC

VCC = V no load

= 0V, V

= V

= 76V,

RS+

= 76V 5 12 µA

RS+

MAX4080F/MAX4081F ±1000

SENSE

MAX4080T/MAX4081T ±250

MAX4080S/MAX4081S ±100

MAX4080F/MAX4081F 5

MAX4080T/MAX4081T 20Gain A

MAX4080S/MAX4081S 60

TA = +25°C ±0.1 ±0.6

VCC = V

(Note 5)

RS+

= 48V

TA = -40°C to +85°C ±1Gain Accuracy ΔA

= T

MIN

to T

MAX

TA = +25°C ±0.1 ±0.6

CMRR V

PSRR V

VCC = V (Note 6)

RS+

= 48V

RS+

= 48V, V

RS+

TA = -40°C to +85°C ±1

= T

MIN

to T

MAX

= 4.5V to 76V 100 124 dB

= 48V, VCC = 4.5V to 76V 100 122 dB

MAX4080F/MAX4081F,

= 1000mV

= 4.5V, V

)

= 48V, V V

REF1B

(sourcing) =

OUT

REF1A

= 2.5V,

RS+

+500µA (Note 8)

SENSE

MAX4080T/MAX4081T,

= 250mV

SENSE

MAX4080S/MAX4081S, V

= 100mV

SENSE

0.15 0.27 V

±1.2

µA

V/V

MAX4080/MAX4081

76V, High-Side, Current-Sense Amplifiers with

Voltage Output

_______________________________________________________________________________________ 3

DC ELECTRICAL CHARACTERISTICS (continued)

(VCC= V

RS+

= 4.5V to 76V, V

REF1A

= V

REF1B

= 5V (MAX4081 only), V

SENSE

= (V

RS+

- V

RS-

) = 0V, R

LOAD

= 100kΩ, TA= T

MIN

MAX

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

OUT Low Voltage V

REF1A = REF1B Input Voltage Range (MAX4081 Only)

REF1A Input Voltage Range (MAX4081 Only)

REF1A Rejection Ratio (MAX4081 Only)

REF/REF1A Ratio (MAX4081 Only)

REF1A Input Impedance (MAX4081 Only)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

REF

GND)

REF1A

GND)

VCC = V V

REF1A

2.5V, V

-1000mV (for MAX4081 only)

Inferred from REF1A rejection ratio, V

REF1A

Inferred from REF1A rejection ratio, V

REF1B

VCC = V V

REF1A

REF1B

= 48V,

RS+

= V

REF1B

SENSE

= V

REF1B

= GND

= 48V, V

RS+

= V

REF1B

= 10V, V

= V

= 48V (Note 2)

RS+

= GND 250 kΩ

I 100µA

SENSE

= 1.5V to 6V

REF1B

OUT

= GND,

(sinking) = 10µA 4 15

(sinking) =

= 0V,

1.5 6 V

312V

80 108 dB

0.497 0.500 0.503

23 55

MAX4080/MAX4081

76V, High-Side, Current-Sense Amplifiers with Voltage Output

4 _______________________________________________________________________________________

AC ELECTRICAL CHARACTERISTICS

(VCC= V

RS+

= 4.5V to 76V, V

REF1A

= V

REF1B

= 5V (MAX4081 only), V

SENSE

= (V

RS+

- V

RS-

) = 0V, R

LOAD

= 100kΩ, C

LOAD

= 20pF,

= T

MIN

to T

MAX

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

Note 1: All devices are 100% production tested at TA= +25°C. All temperature limits are guaranteed by design. Note 2: V

REF

is defined as the average voltage of V

REF1A

and V

REF1B

. REF1B is usually connected to REF1A or GND.

SENSE

is defined as V

RS+

- V

RS-

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 V

SENSE

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

SENSE

Note 4: Negative V

SENSE

applies to MAX4081 only.

Note 5: V

SENSE

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: V

is extrapolated from the gain accuracy test for the MAX4080 and measured as (V

OUT

- V

REF

)/AVat V

SENSE

= 0V, for the

MAX4081.

Note 7: V

SENSE

is:

MAX4080F, 500mV MAX4080T, 125mV MAX4080S, 50mV MAX4081F/T/S, 0V V

REF1B

= V

REF1A

= 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.

Bandwidth BW

OUT Settling Time to 1% of Final Value

Capacitive-Load Stability No sustained oscillations 500 pF

Output Resistance R

Power-Up Time V

Saturation Recovery Time (Notes 9,10) 50 µs

PARAMETER SYMBOL CONDITION MIN TYP MAX UNITS

MAX4080F/T/S 250

MAX4081F/T/S 150

= 100mV ( Note 9) 50 µs

S E NS E

OUT

= V

48V, V

SENSE

= V

C C

RS+

= 2.5V

OUT

= 10mV to 100mV 20

= 100mV to 10mV 20

= 100mV 0.1 Ω

= 48V , V

RS +

kHz

µs

MAX4080/MAX4081

76V, High-Side, Current-Sense Amplifiers with

Voltage Output

_______________________________________________________________________________________ 5

Typical Operating Characteristics

(VCC= V

RS+

= 48V, V

SENSE

= 0V, C

LOAD

= 20pF, R

LOAD

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

INPUT OFFSET VOLTAGE HISTOGRAM

PERCENTAGE (%)

-125 -75 -50 -25-100 0 25 50 75 100 125 INPUT OFFSET VOLTAGE (μV)

MAX4080 toc01

INPUT OFFSET VOLTAGE (μV)

300 250 200 150 100

-50

-100

-150

-200

-250

-300

-50 25 500-25

COMMON-MODE REJECTION RATIO

GAIN ACCURACY vs. V

= 48V

RS+

S VERSION

-0.05

-0.10

GAIN ACCURACY (%)

-0.15

-0.20 476

T VERSION

F VERSION

VCC (V)

MAX4080 toc04

6452402816

-10

-20

-30

-40

-50

-60

-70

-80

-90

-100

-110

COMMON-MODE REJECTION RATIO (dB)

-120

-130 11M

MAX4081F/T/S

REFERENCE REJECTION RATIO

vs. FREQUENCY

-10

-20

-30

-40

-50

-60

-70

-80

-90

REFERENCE REJECTION RATIO (dB)

-100

-110

-120

FREQUENCY (Hz)

MAX4080 toc07

10k1k100101100k

SMALL-SIGNAL GAIN vs. FREQUENCY

SENSE

GAIN (dB)

0.1 1000

INPUT OFFSET VOLTAGE

vs. TEMPERATURE

TEMPERATURE (°C)

MAX4081F/T/S

vs. FREQUENCY

FREQUENCY (Hz)

MAX4080F/T/S

= 10mV

MAX4080S

MAX4080T

MAX4080F

FREQUENCY (kHz)

100 125 150

100101

100k10k1k10010

0.5

0.4

MAX4080 toc02

0.3

0.2

0.1

-0.1

GAIN ACCURACY (%)

-0.2

-0.3

-0.4

-0.5

-50 -25 0 25 50 75 100 125

-10

-20

MAX4080 toc05

-30

-40

-50

-60

-70

-80

-90

-100

-110

POWER-SUPPLY REJECTION RATIO (dB)

-120

-130 11M

MAX4080 toc08

GAIN (dB)

0.1 1000

GAIN ACCURACY vs. TEMPERATURE

TEMPERATURE (°C)

MAX4081F/T/S

POWER-SUPPLY REJECTION RATIO

vs. FREQUENCY

100k10k1k10010

FREQUENCY (Hz)

MAX4081F/T/S

SMALL-SIGNAL GAIN vs. FREQUENCY

= 100mV

OUT

P-P

MAX4081S

MAX4081T

MAX4081F

100101

FREQUENCY (kHz)

MAX4080 toc03

MAX4080 toc06

MAX4080 toc09

MAX4080/MAX4081

76V, High-Side, Current-Sense Amplifiers with Voltage Output

6 _______________________________________________________________________________________

Typical Operating Characteristics (continued)

(VCC= V

RS+

= 48V, V

SENSE

= 0V, C

LOAD

= 20pF, R

LOAD

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

42816 40 52 64 76

MAX4080

SUPPLY CURRENT vs. V

MAX4080 toc10

VCC (V)

SUPPLY CURRENT (μA)

NO LOAD V

SENSE

= 0V

MAX4080 toc11

VCC (V)

SUPPLY CURRENT (μA)

645216 28 40

100

105

110

115

120

125

476

MAX4081

SUPPLY CURRENT vs. V

REF

= 2.5V NO LOAD V

SENSE

= 0V

110

105

100

115

-50 -25 0 25 50 75 100 125

MAX4080

SUPPLY CURRENT vs. TEMPERATURE

MAX4080 toc12

TEMPERATURE (°C)

SUPPLY CURRENT (μA)

110

105

100

115

-50 -25 0 25 50 75 100 125

MAX4081

SUPPLY CURRENT vs. TEMPERATURE

MAX4080 toc13

TEMPERATURE (°C)

SUPPLY CURRENT (μA)

REF1A

= V

REF1B

= 2.5V

MAX4080 toc14

OUT

(SOURCING) (mA)

OUT

HIGH VOLTAGE (V

- V

) (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

01.0

OUT

HIGH VOLTAGE

vs. I

OUT

(SOURCING)

VCC = 4.5V

TA = +125°C

TA = +85°C

TA = +25°C

TA = 0°C

TA = -40°C

45040035030025020015010050

100

150

200

250

300

0 500

OUT

LOW VOLTAGE

vs. I

OUT

(SINKING)

MAX4080 toc15

OUT

(SINKING) (μA)

OUT

LOW VOLTAGE (mV)

TA = +125°C

TA = +85°C

TA = +25°C

TA = 0°C

TA = -40°C

VCC = 4.5V

MAX4080 toc16

INPUT

5mV/div

OUTPUT

25mV/div

20μs/div

MAX4080F

SMALL-SIGNAL TRANSIENT RESPONSE

MAX4080 toc17

INPUT

5mV/div

OUTPUT

100mV/div

20μs/div

MAX4080T

SMALL-SIGNAL TRANSIENT RESPONSE

MAX4080 toc18

INPUT

5mV/div

OUTPUT

300mV/div

20μs/div

MAX4080S

SMALL-SIGNAL TRANSIENT RESPONSE

MAX4080/MAX4081

76V, High-Side, Current-Sense Amplifiers with

Voltage Output

_______________________________________________________________________________________ 7

Typical Operating Characteristics (continued)

(VCC= V

RS+

= 48V, V

SENSE

= 0V, C

LOAD

= 20pF, R

LOAD

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

INPUT

10mV/div

OUTPUT

50mV/div

INPUT

400mV/div

MAX4081F

SMALL-SIGNAL TRANSIENT RESPONSE

20μs/div

MAX4080 toc19

MAX4080F

LARGE-SIGNAL TRANSIENT RESPONSE

MAX4080 toc22

INPUT

2.5mV/div

OUTPUT

50mV/div

INPUT

100mV/div

MAX4081T

SMALL-SIGNAL TRANSIENT RESPONSE

20μs/div

MAX4080 toc20

MAX4080T

LARGE-SIGNAL TRANSIENT RESPONSE

MAX4080 toc23

SMALL-SIGNAL TRANSIENT RESPONSE

MAX4081S

INPUT

1mV/div

OUTPUT

50mV/div

20μs/div

MAX4080S

LARGE-SIGNAL TRANSIENT RESPONSE

INPUT

33mV/div

MAX4080 toc21

MAX4080 toc24

OUTPUT

2V/div

INPUT

400mV/div

OUTPUT

2V/div

20μs/div

MAX4081F

LARGE-SIGNAL TRANSIENT RESPONSE

20μs/div

MAX4080 toc25

OUTPUT

2V/div

INPUT

100mV/div

OUTPUT

2V/div

20μs/div

MAX4081T

LARGE-SIGNAL TRANSIENT RESPONSE

20μs/div

MAX4080 toc26

OUTPUT

2V/div

20μs/div

MAX4081S

LARGE-SIGNAL TRANSIENT RESPONSE

INPUT

33mV/div

OUTPUT

2V/div

20μs/div

MAX4080 toc27

MAX4080/MAX4081

76V, High-Side, Current-Sense Amplifiers with Voltage Output

8 _______________________________________________________________________________________

Typical Operating Characteristics (continued)

(VCC= V

RS+

= 48V, V

SENSE

= 0V, C

LOAD

= 20pF, R

LOAD

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

MAX4080 toc28

4μs/div

VCC-TRANSIENT RESPONSE

5V/div

OUT

1V/div

RS+

= 20V

= 20V STEP

REF1

= V

REF2

= 2.5V

VCC = 40V

VCC = 20V

MAX4080 toc29

INPUT

500mV/div

OUTPUT

2V/div

20μs/div

MAX4080F

SATURATION RECOVERY RESPONSE

= 4.5V)

MAX4080 toc30

(0 TO 10V)

5V/div

OUTPUT

2.5V/div

100μs/div

MAX4080T

STARTUP DELAY

SENSE

= 250mV)

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 current 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 unidirectionally, 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 (V

RS+

). Highside 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 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 V

REF

to VCC, while discharge current is given from V

REF

GND. Measurements of OUT with respect to V

REF

yield a positive 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 R

SENSE

to the load (Figure 2), cre-

ating a sense voltage, V

SENSE

. 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 V

SOURCE

- (I

LOAD

)(R

SENSE

). The amplifier’s open-loop gain forces its noninverting input to the same voltage as the inverting input. Therefore, the drop across RG1 equals V

SENSE

. The internal current mirror

multiplies I

RG1

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, R

SENSE

, 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 measurement of the sense voltage is achieved. In the following amplifier stages of the MAX4081, the output signal of amplifier A2 is levelshifted to the reference voltage (V

REF

= V

REF1A

REF1B

), resulting in a voltage at the output pin (OUT)

MAX4080/MAX4081

76V, High-Side, Current-Sense Amplifiers with

Voltage Output

_______________________________________________________________________________________ 9

Pin Description

MAX4080 MAX4081

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

22 V

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

4 4 GND Ground

5 5 OUT

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

— 6 REF1B

— 7 REF1A

NAME FUNCTION

Supply Voltage Input. Decouple V bypass line transients.

Voltage Output. For the unidirectional MAX4080, V V

. For the bidirectional MAX4081, the difference voltage (V

SENSE

proportional to V

Reference Voltage Input: Connect REF1B to REF1A or to GND (see the External Reference section).

Reference Voltage Input: Connect REF1A and REF1B to a fixed reference voltage (V Reference section).

REF

). V

and indicates the correct polarity.

SENSE

is equal to V

OUT

to GND with at least a 0.1µF capacitor to

when V

REF

is proportional to

OUT

is zero (see the External

SENSE

- V

REF

) is

OUT

MAX4080/MAX4081

that swings above V

REF

voltage for positive-sense volt-

ages and below V

REF

for negative-sense voltages.

OUT

is equal to V

REF

when V

SENSE

is equal to zero.

Set the full-scale output range by selecting R

SENSE

and the appropriate gain version of the MAX4080/ MAX4081.

76V, High-Side, Current-Sense Amplifiers with Voltage Output

10 ______________________________________________________________________________________

Figure 1. MAX4081T OUT Transfer Curve

Figure 3. MAX4081 Functional Diagram

Figure 2. MAX4080 Functional Diagram

4.5V TO 76V BATTERY

LOAD

SENSE

MAX4081T

GND

RS+RS-

REF1A

REF1B

LOAD

CURRENT

MIRROR

SENSE

RS+

RS-

MAX4080

A3A2

CHARGE

OUT

SYSTEM LOAD AND CHARGER

OUT

10V

-250mV 250mV

= GND

OUT

DISCHARGE CURRENT

RS+

Q1 Q2

CURRENT

MIRROR

-5V

SENSE

RS-

CURRENT

MIRROR

CHARGE CURRENT

REF

- V

OUT

REF1A

= 10V

OUT

SENSE

= V

REF1B

MAX4081

= 5V

OUT

125kΩ

REF1B

125kΩ

REF1A

GND

REF

MAX4080/MAX4081

76V, High-Side, Current-Sense Amplifiers with

Voltage Output

______________________________________________________________________________________ 11

Table 1. Typical Component Values

External References (MAX4081)

For the bidirectional MAX4081, the V

OUT

reference level

is controlled by REF1A and REF1B. V

REF

is defined as

the average voltage of V

REF1A

and V

REF1B

. Connect REF1A and REF1B to a low-noise, regulated voltage source to set the output reference level. In this mode, V

OUT

equals V

REF1A

when V

SENSE

equals zero (see

Figure 4).

Alternatively, connect REF1B to ground, and REF1A to a low-noise, regulated voltage source. In this case, the output reference level (V

REF

) is equal to V

REF1A

divided by

two. V

OUT

equals V

REF1A

/2 when V

SENSE

equals zero.

In either mode, the output swings above the reference voltage for positive current-sensing (V

RS+

> V

RS-

). The output swings below the reference voltage for negative current-sensing (V

RS+

< V

RS-

Applications Information

Recommended Component Values

Ideally, the maximum load current develops the fullscale sense voltage across the current-sense resistor. Choose the gain needed to yield the maximum output voltage required for the application:

OUT

= V

SENSE

✕ A

where V

SENSE

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 AVis the gain of the device.

In applications monitoring a high current, ensure that R

SENSE

is able to dissipate its own I2R loss. If the resistor’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.

FULL-SCALE LOAD

CURRENT, I

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, I

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

LOAD

(A)

CURRENT-SENSE

RESISTOR (mΩ)

CURRENT-SENSE

RESISTOR (mΩ)

GAIN

(V/V)

GAIN

(V/V)

FULL-SCALE

SENSE

(mV)

FULL-SCALE

SENSE

(mV)

MAX4081 FULL-SCALE

OUTPUT VOLTAGE

- V

OUT

MAX4080 FULL-SCALE OUTPUT VOLTAGE (V)

REF,

MAX4080/MAX4081

The full-scale output voltage is V

OUT

= R

SENSE

✕ I

LOAD

(MAX)

✕ A

, for the MAX4080 and V

OUT

= V

REF

SENSE

✕ I

LOAD(MAX)

✕ A

for the MAX4081.

SENSE(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 R

SENSE

based on the following criteria:

• Voltage Loss: A high R

SENSE

value causes the power-source voltage to degrade through IR loss. For minimal voltage loss, use the lowest R

SENSE

value.

• Accuracy: A high R

SENSE

value allows lower currents to be measured more accurately. This is due to offsets becoming less significant when the sense voltage is larger. For best performance, select R

SENSE

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 R

SENSE

can be significant. Take this into consideration when choosing the resistor 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 I

SENSE

has a large high-frequency component. Wire-wound resistors have the highest inductance, while metal film is somewhat better. Low-inductance, metal-film resistors are also available. Instead of being spiralwrapped around a core, as in metal-film or wirewound resistors, they are a straight band of metal and are available in values under 1Ω.

Because of the high currents that flow through R

SENSE

, take care to eliminate parasitic trace resistance from causing errors in the sense voltage. Either use a fourterminal current-sense resistor or use Kelvin (force and sense) PC board layout techniques.

Dynamic Range Consideration

Although the MAX4081 have fully symmetrical bidirectional V

SENSE

input capability, the output voltage range is usually higher from REF to VCCand 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 VCCto GND with a 0.1µF ceramic capacitor. In many applications, VCCcan be connected to one of the current monitor terminals (RS+ or RS-). Because VCCis independent of the monitored voltage, VCCcan be connected to a separate regulated supply.

If VCCwill 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 conjunction with a 0.1µF bypass capacitor work well.

The MAX4080/MAX4081 require no special considerations with respect to layout or grounding. Consideration should be given to minimizing errors due to the large charge and discharge currents in the system.

76V, High-Side, Current-Sense Amplifiers with Voltage Output

12 ______________________________________________________________________________________

Figure 4. MAX4081 Reference Inputs

LOAD

= 0

LOAD

= 0

SENSE

RS-RS+

MAX4081

GND

REF1A

REF1B

OUT

LOAD

GND

SENSE

RS-RS+

REF1A

MAX4081

REF1B

OUT

LOAD

10V

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.

MAX4080/MAX4081

76V, High-Side, Current-Sense Amplifiers with

Voltage Output

______________________________________________________________________________________ 13

Typical Operating Circuit

Chip Information

TRANSISTOR COUNT: 185

PROCESS: Bipolar

Selector Guide

Figure 5. MAX4081 Used In Smart-Battery Application

PART GAIN (V/V) I

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

SENSE

RS-RS+

MAX4081

REF1A

GND

1.8V

OUT

ADC

MAX1243

μC

REF1B

SYSTEM

POWER

MANAGEMENT

AND

CHARGER

CIRCUITRY

SERIAL

INTERFACE

SENSE

VCC = 4.5V TO 76V

SENSE

SYSTEM

LOAD

RS-RS+

BATTERY

MAX4080

OUT

GND

MAX4080/MAX4081

76V, High-Side, Current-Sense Amplifiers with Voltage Output

14 ______________________________________________________________________________________

Package Information

(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.)

E H

Ø0.50±0.1

0.6±0.1

TOP VIEW

FRONT VIEW

4X S

BOTTOM VIEW

SIDE VIEW

DIM

A A1 A2 b

c D e

INCHES

MIN

0.002

0.030

0.010

0.005

0.116

0.0256 BSC

0.116

0.188

0.016 0°

0.0207 BSC

MAX

0.043

0.006

0.037

0.014

0.007

0.120

0.198

0.026 6°

MILLIMETERS

MIN

0.05 0.15

0.25 0.36

0.13 0.18

2.95 3.05

4.78

0.41

MAX

- 1.10

0.950.75

0.65 BSC

5.03

0.66

0.5250 BSC

8LUMAXD.EPS

6°0°

PROPRIETARY INFORMATION

TITLE:

PACKAGE OUTLINE, 8L uMAX/uSOP

21-0036

REV.DOCUMENT CONTROL NO.APPROVAL

MAX4080/MAX4081

76V, High-Side, Current-Sense Amplifiers with

Voltage Output

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.

Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 15

Package Information (continued)

(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.)

TOP VIEW

FRONT VIEW

INCHES

DIM

MIN

0.053A

0.004

0.014

0.007

C e 0.050 BSC 1.27 BSC

0.150

E H 0.2440.228 5.80 6.20

0.016L

VARIATIONS:

INCHES

MINDIM

0.189 0.197 AA5.004.80 8

0.337 0.344 AB8.758.55 14

0∞-8∞

SIDE VIEW

MAX

0.069

0.010

0.019

0.010

0.157

0.050

MAX

0.3940.386D

MILLIMETERS

MAX

MIN

1.35

1.75

0.10

0.25

0.35

0.49

0.19

0.25

3.80 4.00

0.40 1.27

MILLIMETERS

MAX

MIN

9.80 10.00

N MS012

SOICN .EPS

PROPRIETARY INFORMATION

TITLE:

PACKAGE OUTLINE, .150" SOIC

21-0041

REV.DOCUMENT CONTROL NO.APPROVAL

MAXIM MAX4080, MAX4081 Technical data

Specifications and Main Features

Frequently Asked Questions

User Manual