The input stage of the AMC3330 feeds a second-order, switched-capacitor, feed-forward ΔΣ modulator. The modulator converts the analog signal into a bitstream that is transferred over the isolation barrier, as described in the Isolation Channel Signal Transmission section. The high-impedance, and low bias-current input of the AMC3330 makes the device suitable for isolated, high-voltage-sensing applications that typically employ high-impedance resistor dividers.

There are two restrictions on the analog input signals (INP and INN). First, if the input voltage exceeds the input range specified in the Absolute Maximum Ratings table, the input current must be limited to 10 mA because the device input electrostatic discharge (ESD) diodes turn on. Second, the linearity and noise performance of the device are ensured only when the differential analog input voltage remains within the specified linear full-scale range V_FSR and within the specified input common-mode voltage range V_CM as specified in the Recommended Operating Conditions table.