Datasheet

AD8207
Rev. 0 | Page 13 of 16
EXTERNAL REFERENCED OUTPUT
Tying both reference pins together and to an external reference
produces an output equal to the reference voltage when there is
no differential input (see Figure 30). The output moves down
from the reference voltage when the input is negative, relative
to the −IN pin, and up when the input is positive, relative to the
−IN pin. The reference pins are connected to the positive input
of the main amplifier via precision-trimmed 100 kΩ resistors.
Therefore, it is recommended that a low impedance voltage is
always be used to set the reference voltage. If external resistors
are connected directly to the V
REF
1 and V
REF
2 pins, there will
be a mismatch with the internal trimmed resistors, leading to
offset gain accuracy reduction.
RANGE
V+
5
V
REF
+IN
–IN
OUT
VOLTAGE
REFERENCE
GND
AD8207
ZERO
DRIFT
V
REF
1
V
REF
2
2.5V
09160-014
Figure 30. External Referenced Output, V+ = 5 V
SPLITTING THE SUPPLY
By tying one reference pin to V+ and the other to the ground
pin, the output is set at half of the supply when there is no dif-
ferential input (see Figure 31). The benefit is that no external
reference is required to offset the output for bidirectional current
measurement. This creates a midscale offset that is ratiometric to
the supply, which means that if the supply increases or decreases,
the output remains at half the supply. For example, if the supply is
5.0 V, the output is at half scale, or 2.5 V. If the supply increases by
10% (to 5.5 V), the output goes to 2.75 V.
RANGE
V+
5
V
REF
+IN
–IN
OUT
GND
AD8207
ZERO
DRIFT
V
REF
1
V
REF
2
09160-015
Figure 31. Splitting the Supply, V+ = 5 V
SPLITTING AN EXTERNAL REFERENCE
In Figure 32, an external reference is divided by 2 with an
accuracy of approximately 0.5% by connecting one V
REF
pin to
ground and the other V
REF
pin to the reference (see Figure 32).
V+
5
V
REF
+IN
–IN
OUT
VOLTAGE
REFERENCE
GND
AD8207
ZERO
DRIFT
V
REF
1
V
REF
2
5V
09160-016
RANGE
Figure 32. Splitting an External Reference, V+ = 5 V