Single/Dual/Quad, High-Side Current-Sense

Amplifiers with Internal Gain

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Detailed Description

The MAX4376/MAX4377/MAX4378 high-side current-

sense amplifiers feature a 0 to +28V input common-mode

range that is independent of supply voltage. This feature

allows the monitoring of current out of a battery in deep

discharge and also enables high-side current sensing at

The MAX4376/MAX4377/MAX4378 operate as follows:

load (Figure 1). 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

The amplifier’s open-loop gain forces its noninverting

input to the same voltage as the inverting input.

Therefore:

where amp gain is 2, 5, or 10.

The part’s gain equals (

β x RGD / RG1) x amp gain.

Therefore:

where GAIN = 20 for MAX437_T.

GAIN = 50 for MAX437_F.

GAIN = 100 for MAX437_H.

the appropriate gain version of the MAX4376/

MAX4377/MAX4378.

Applications Information

Recommended Component Values

The MAX4376/MAX4377/MAX4378 sense a wide variety

of currents with different sense resistor values. Table 1

lists common resistor values for typical operation of the

MAX4376/MAX4377/MAX4378.

To measure lower currents more accurately, use a high

sense voltage that reduces offset voltage errors of the

internal op amp.

rated power dissipation is exceeded, its value may drift

or it may fail altogether, causing a differential voltage

across the terminals in excess of the absolute maxi-

mum ratings.

have the highest inductance, metal-film resistors are

somewhat better, and low-inductance metal-film resis-

tors are best suited for these applications.

Bidirectional Current-Sense Amplifier

Systems such as laptop computers and other devices

that have internal charge circuitry require a precise

bidirectional current-sense amplifier to monitor accu-

rately the battery’s current regardless of polarity. Figure

2 shows the MAX4377 used as a bidirectional current

Pin Description

PIN

MAX4376

MAX4376

MAX4377

MAX4378

SOT23-5

SO-8

µMAX-8/

SO-8

SO-14/

TSSOP-14

NAME

FUNCTION

1

4

1, 7

1, 7, 8, 14

OUT, OUT_

reversal).

2

3

4

11

GND

Ground

3184

Supply Voltage

4

8

3, 5

3, 5, 10, 12

RS+, RS_+

Power connection to the external sense resistor

5

6

2, 6

2, 6, 9, 13

RS-, RS_-

Load-side connection to the external sense resistor

—

2, 5, 7

——

N.C.

No Connection. Not internally connected.