APPARATUS FOR DETECTING VARIATION OF CAPACITANCE MULTI CHANNEL

摘要

A device for detecting the capacitance change of multi-channel is provided to prevent simultaneous operations by one pin in operating plural detecting devices in parallel, by setting an output mode. A device for detecting the change of capacitance of multi-channel has plural capacitance change detection modules. The capacitance change detection module is composed of a dual frequency generating unit generating detection frequency(fa) and detection frequency(fb) k times as slow as the detection frequency(fa) about the capacitance change of a capacitor by time division; a difference frequency operation unit calculating difference frequency between the detection frequencies; a difference frequency change rate operation unit having a reference frequency generating unit and a difference frequency change rate calculating unit; a detection level input stage; a comparing unit comparing the detection level input to the detection level input stage with the change rate of difference frequency calculated in the difference frequency change rate operation unit; an output stage converting a high signal into a low signal if the change rate of difference frequency is higher than the detection level, according to the result of the comparing unit and outputting the converted low signal; a dual frequency generation cycle varying unit increasing a generation cycle of the detection frequency(fa) generated from the dual frequency generating unit for a predetermined time from when the change rate of difference frequency gets higher or lower than the detection level; and an enable signal input/output unit enabling the detection module according to the voltage applied from the outside or outputting an enable signal to the outside. A synchronous control unit(230) synchronizes the detecting devices to prevent the detecting devices from being operated at the same time in operating the detecting devices in parallel or sets an output mode of the detecting device in individually operating the detecting device.