CAPACITANCE MEASURING CIRCUIT FOR TOUCH SENSOR

摘要

PURPOSE: A capacitance measurement circuit of a touch sensor and a capacitance measurement method are provided to use OP AMP in which the current consumption smalls and reduce or remove the parasitic capacitance. CONSTITUTION: A condenser part repeatedly charge and discharge for a capacitance. A sensor unit is composed so that the capacitance of the condenser part is changed in response to react to the access of the outer conductor. An amplifier(20) has differential inputs to output the capacitance integrated and amplified. A reference condenser(30) returns negatively the output of an amplifier to an input side of the amplifier. A reset switch(40) discharges the capacitance of the reference condenser. The reset switch discharges the capacitance of the reference condenser when the capacitance is abnormal state or the rate of the output capacitance of the capacitance comparison amplifier is over than designated rate.