Figure 56 shows a simplified circuit typically used in high-voltage-sensing applications. The high impedance resistors (R1 and R2) are used as voltage dividers and dominate the current value definition. The resistance of the sensing resistor R3 is chosen to meet the input voltage range of the AMC1304. This resistor and the differential input impedance of the device (the AMC1304x25 is 25 kΩ, the AMC1304x05 is 5 kΩ) also create a voltage divider that results in an additional gain error. With the assumption of R1, R2, and RIN having a considerably higher value than R3, the resulting total gain error can be estimated using Equation 4, with EG being the gain error of the AMC1304.
This gain error can be easily minimized during the initial system-level gain calibration procedure.