AD8205

Rev. 0 | Page 9 of 12

OUTPUT OFFSET ADJUSTMENT

The output of the AD8205 can be adjusted for unidirectional or

bidirectional operation.

UNIDIRECTIONAL OPERATION

Unidirectional operation allows the AD8205 to measure cur-

rents through a resistive shunt in one direction. The basic

modes for unidirectional operation are ground referenced

output mode and V+ referenced output mode.

In the case of unidirectional operation, the output could be set

at the negative rail (near ground) or at the positive rail (near

V+) when the differential input is 0 V. The output moves to the

opposite rail when a correct polarity differential input voltage is

applied. In this case, full scale is approximately 100 mV. 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 is positive to move the

output up.

GROUND REFERENCED OUTPUT

When using the AD8205 in this mode, both reference 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 14).

AD8205

+IN

–IN

NC

NC = NO CONNECT

GND

V+

OUT

Figure 14. Ground Referenced Output

Table 4. V+ = 5 V

0 V

0.05 V

100 mV

4.8 V

V+ REFERENCED OUTPUT

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

tive 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 15).

AD8205

+IN

–IN

NC

NC = NO CONNECT

GND

V+

OUT

Figure 15. V+ Referenced Output

Table 5. V+ = 5 V

0 V

4.8 V

100 mV

0.05 V

BIDIRECTIONAL OPERATION

Bidirectional operation allows the AD8205 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.

+40 mV

4.5 V

−40 mV

0.5 V

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

the reference inputs.

internal offset node. There is no operational difference between

the pins.