1µA, 4-Bump UCSP/SOT23,

Precision Current-Sense Amplifier

6

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Detailed Description

The MAX9634 unidirectional high-side, current-sense

amplifier features a 1.6V to 28V input common-mode

range. This feature allows the monitoring of current out

of a battery with a voltage as low as 1.6V. The

MAX9634 monitors current through a current-sense

resistor and amplifies the voltage across that resistor.

The MAX9634 is a unidirectional current-sense amplifier

that has a well-established history. An op amp is used

to force the current through an internal gain resistor at

equals the voltage drop across an external sense resis-

FET. Its source current is the same as its drain current,

MAX9634T, 50V/V for the MAX9634F, 100V/V for the

MAX9634H, and 200V/V for the MAX9634W. The output

is protected from input overdrive by use of an output

current-limiting circuit of 7mA (typical) and a 6V clamp

protection circuit.

Applications Information

Choosing the Sense Resistor

Voltage Loss

to drop due to IR loss. For minimal voltage loss, use the

GAIN

(V/V)

(

Ω)

(k

Ω)

200

100

20

100

100

10

50

200

10

25

400

10

Table 1. Internal Gain-Setting Resistors

(Typical Values)

Typical Operating Circuit

GND

OUT

P

MAX9634

RS+

RS-

ADC

LOAD

µC

10k

Ω