Data Sheet

AD8418

OUTPUT OFFSET ADJUSTMENT

The output of the AD8418 can be adjusted for unidirectional or

bidirectional operation.

UNIDIRECTIONAL OPERATION

Unidirectional operation allows the AD8418 to measure currents

through a resistive shunt in one direction. The basic modes for

unidirectional operation are ground referenced output mode

For unidirectional operation, the output can be set at the negative

differential input is 0 V. The output moves to the opposite rail

when a correct polarity differential input voltage is applied. The

required polarity of the differential input depends on the output

voltage setting. If the output is set at the positive rail, the input

polarity needs to be negative to move the output down. If the

output is set at ground, the polarity must be positive to move

the output up.

Ground Referenced Output

When using the AD8418 in this mode, both referenced inputs are

tied to ground, which causes the output to sit at the negative rail

when there are zero differential volts at the input (see Figure 27).

–

+

R1

OUT

GND

AD8418

R2

R3

R4

–IN

+IN

Figure 27. Ground Referenced Output

This mode is set when both reference pins are tied to the positive

supply. It is typically used when the diagnostic scheme requires

detection of the amplifier and the wiring before power is applied to

the load (see Figure 28).

–

+

R1

OUT

GND

AD8418

R2

R3

R4

–IN

+IN

BIDIRECTIONAL OPERATION

Bidirectional operation allows the AD8418 to measure currents

through a resistive shunt in two directions.

In this case, the output is set anywhere within the output range.

Typically, it is set at half-scale for equal range in both directions.

In some cases, however, it is set at a voltage other than half scale

when the bidirectional current is nonsymmetrical.

Adjusting the output is accomplished by applying voltage(s) to

the referenced inputs.

internal offset node. There is no operational difference between

the pins.

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