AMC1100_15 Datasheet, PDF (14/33 Pages) Texas Instruments – AMC1100 Fully-Differential Isolation Amplifier

AMC1100
SBAS562A – APRIL 2012 – REVISED DECEMBER 2014
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7.4 Device Functional Modes
The AMC1100 is powered on when the supplies are connected. The device is operated off a 5-V nominal supply
on the high-side. The potential of the ground reference GND1 can be floating, which is usually the case in shunt-
based current-measurement applications. TI recommends tying one side of the shunt to the GND1 pin of the
AMC1100 to maintain the operating common-mode range requirements of the device.
The low-side of the AMC1100 can be powered from a supply source with a nominal voltage of 3.0 V, 3.3 V, or
5.0 V. When operated at 5 V, the common-mode voltage of the output stage is set to 2.55 V nominal; in both
other cases, the common-mode voltage is automatically set to 1.29 V.
Although usually applied in shunt-based current-sensing circuits, the AMC1100 can also be used for isolated
voltage measurement applications, as shown in a simplified way in Figure 32. In such applications, usually a
resistor divider (R₁ and R₂ in Figure 32) is used to match the relatively small input voltage range of the
AMC1100. R₂ and the AMC1100 input resistance (R_IN) also create a resistance divider that results in additional
gain error. With the assumption that R₁ and R_IN have a considerably higher value than R₂, the resulting total gain
error can be estimated using Equation 1:
G_ERRTOT
=
G_ERR
+
R₂
R_IN
where:
• G_ERR = device gain error.
(1)
L1
R₁
R₂
R_IN
L2
Figure 32. Voltage Measurement Application
14
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