CAPACITIVE OBJECT SENSING SYSTEM AND CORRESPONDING METHOD

摘要

An electric field object sensing system (1) and method. The system (1) comprises a transmitter electrode (2), a receiver electrode (4), a switching circuit (32) coupled to the receiver electrode, an alternating voltage source (3) coupled to the transmitter electrode (2) and the switching circuit (32), and an output connection (34) coupled to the receiver electrode (4). Charge pumping performed according to the alternating voltage cycle provides a voltage over a capacitor (43) of the switching circuit (32) that increases dependent upon the capacitive coupling between the transmitter electrode (2) and the receiver electrode (4). The voltage over the capacitor (43) of the switching circuit (32) is allowed to saturate, and the saturated voltage is used as an output (20) that varies when an object (8) is in the vicinity of the transmitter and receiver electrodes. The output (20) may be fed to a high impedance read-out means e.g. an ADC (24). The system (1) may be implemented in CMOS and integrated in control circuits of electronic products.