Data Sheet AD8216
Rev. C | Page 11 of 16
OUTPUT OFFSET ADJUSTMENT
The output of the AD8216 can be adjusted for unidirectional or
bidirectional operation.
UNIDIRECTIONAL OPERATION
Unidirectional operation allows the AD8216 to measure currents
through a resistive shunt in one direction. The basic modes for
unidirectional operation are ground referenced output mode
and V+ referenced output mode.
For unidirectional operation, the output can 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 1.6 V. T h e r equired
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 AD8216 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 24).
AD8216
+IN
–IN
NC
NC = NO CONNECT
GND
V+
OUT
V
REF
1
V
REF
2
07062-029
Figure 24. Ground Referenced Output
Table 4. V+ = 5 V
V
IN
(Referred to −IN) V
OUT
0 V 0.1 V
1.6 V 4.8 V
V+ REFERENCED OUTPUT
The V+ 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 25).
AD8216
+IN
–IN
NC
NC = NO CONNECT
GND
V+
OUT
V
REF
1
V
REF
2
07062-030
Figure 25. V+ Referenced Output
Table 5. V+ = 5 V
V
IN
(Referred to −IN) V
OUT
0 V 4.9 V
−1.6 V 0.1 V
BIDIRECTIONAL OPERATION
Bidirectional operation allows the AD8216 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.
Table 6. V+ = 5 V, V
OUT
= 2.5 V with V
IN
= 0 V
V
IN
(Referred to −IN) V
OUT
+800 mV 4.9 V
−800 mV 0.1V
Adjusting the output is accomplished by applying voltage(s) to
the referenced inputs.
V
REF
1 and V
REF
2 are tied to internal resistors that connect to an
internal offset node. There is no operational difference between
the pins.
