INTEGRATABLE CAPACITIVE TOUCH SENSING CIRCUIT THROUGH CHARGE SHARING

摘要

An integratable capacitive touch sensing circuit through charge sharing is provided, including a charge sharing circuit, voltage-controlled oscillator, reference frequency generator, switch clock generator and frequency compare circuit; wherein charge sharing circuit further including a sensing capacitor, touch capacitor, share capacitor, charging switch, charge sharing switch and discharging switch, for sharing charge from charged sensing capacitor with discharged share capacitor through charge sharing to accumulate voltage on share capacitor. The capacitance of share capacitor is adjustable for applications generating different sensing capacitance. The charging switch, charge sharing switch and discharging switch are controlled by non-overlapping clocks. Prolonging close duration of charging switch and minimizing close duration of charge sharing switch and discharging switch can minimize interference from ambient noise. The charge sharing circuit finishes charge sharing in a clock cycle and voltage of share capacitor are linear to sensing capacitance and touch capacitance.

主权项

1. An integratable capacitive touch sensing circuit through charge sharing, comprising:
a charge sharing circuit, further comprising a sensing capacitor and a share capacitor, and sharing charge from the charged sensing capacitor with the discharged share capacitor through charge sharing to accumulate voltage on the share capacitor; a voltage-controlled oscillator (VCO), coupled to the share capacitor of the charge sharing circuit and generating an output frequency having a linear relation to the capacitance of the sensing capacitor of the charge sharing circuit; a reference frequency generator, providing a reference voltage; a frequency compare circuit, coupled to the output end of the VCO and the reference frequency provided by the reference frequency generator to count respectively the output frequency of the VCO and the reference frequency; when the output frequency of the VCO changing because of a finger touching, a touch event is detected; and a switch clock generator, coupled VCO and generating non-overlapping switch clocks according to the output of the VCO.