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 34. In such applications, usually a resistor divider (R₁ and R₂ in Figure 34) 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:

Equation 1.

where

• G_ERR = device gain error.

Figure 34. Voltage Measurement Application