9.2.2.1 Design Requirements

Figure 59 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 AMC1306. This resistor and the differential input impedance of the device (the AMC1306x25 is 22 kΩ, the AMC1306x05 is 4.9 kΩ) also create a voltage divider that results in an additional gain error. With the assumption of R1, R2, and R_IN having a considerably higher value than R3, the resulting total gain error can be estimated using Equation 4, with E_G being the gain error of the AMC1306.

Equation 4.

This gain error can be easily minimized during the initial system-level gain calibration procedure.