Data Sheet

AD8417-2

OUTPUT OFFSET ADJUSTMENT

analog.com

Rev. 0 | 11 of 15

The output of the AD8417-2 can be adjusted for unidirectional or

bidirectional operation.

UNIDIRECTIONAL OPERATION

Unidirectional operation allows the AD8417-2 to measure currents

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

unidirectional operation are ground referenced output mode and VS

referenced output mode.

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

rail (near ground) or at the positive rail (near VS) when the differen-

tial 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 must

be negative to decrease the output. If the output is set at ground,

the polarity must be positive to increase the output.

Ground Referenced Output Mode

When using the AD8417-2 in ground referenced output 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).

Figure 27. Ground Referenced Output

VS Referenced Output Mode

VS referenced output 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).

Figure 28. VS Referenced Output

BIDIRECTIONAL OPERATION

Bidirectional operation allows the AD8417-2 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.

Apply voltage(s) to the referenced inputs to adjust the output. VREF1

and VREF2 are tied to internal resistors that connect to an internal

offset node. There is no operational difference between the pins.

EXTERNAL REFERENCED OUTPUT

Tying both pins together and to a reference produces an output

equal to the reference voltage when there is no differential input

(see Figure 29). The output decreases the reference voltage when

the input is negative, relative to the −IN pin, and increases when the

input is positive, relative to the −IN pin.

Figure 29. External Referenced Output