CAPACITIVE SENSOR SYSTEM WITH IMPROVED CAPACITANCE MEASURING SENSITIVITY

摘要

A capacitance sensor system and method includes a capacitive sensor as an array of sensor electrodes E1 (1) near the surface of the integrated circuit and charge pump circuits (5) for measuring the capacitance C14 (20) at each sensor electrode. Shield electrodes E4 (4) and unused sense electrodes are used for background capacitance cancellation at each array location. The shield electrodes E4 (4) are switched between the circuit supply potentials in a manner synchronous to the capacitance sensing at the sense electrodes. The improved background capacitance cancellation allows all circuitry to be located outside the sensor array. The capacitance data is used to determine the positions of fingerprint artifacts and other fingerprint features.