Capacitance sensing method

Abstract

A capacitance sensing method is provided. The capacitance sensing method includes the following steps. During at least one first period of a sensing period, a capacitance under test is sensed through a first sensing channel, and a reference capacitance is sensed through a second sensing channel. During at least one second period of the sensing period, the reference capacitance is sensed through the first sensing channel, and the capacitance under test is sensed through the second sensing channel. A first difference is generated according to the capacitance under test and the reference capacitance.

What is claimed is: 
     
         1 . A capacitance sensing method, comprising:
 sensing a capacitance under test through a first sensing channel and sensing a reference capacitance through a second sensing channel during at least one first period of a sensing period;   sensing the reference capacitance through the first sensing channel and sensing the capacitance under test through the second sensing channel during at least one second period of the sensing period; and   generating a first difference according to the capacitance under test and the reference capacitance.   
     
     
         2 . The capacitance sensing method according to  claim 1 , wherein the first sensing channel comprises a first charge-to-voltage converting unit, the second sensing channel comprises a second charge-to-voltage converting unit, and the capacitance sensing method further comprises:
 converting the capacitance under test into the voltage under test through the first charge-to-voltage converting unit and converting the reference capacitance into the reference voltage through the second charge-to-voltage converting unit during the first period; and   converting the reference capacitance into the reference voltage through the first charge-to-voltage converting unit and converting the capacitance under test into the voltage under test through the second charge-to-voltage converting unit during the second period,   wherein in the step of generating the first difference, the voltage under test and the reference voltage are compared to generate the first difference.   
     
     
         3 . The capacitance sensing method according to  claim 1 , wherein the first periods and the second periods of the sensing period are alternately arranged. 
     
     
         4 . The capacitance sensing method according to  claim 1 , wherein the output of the first sensing channel and the output of the second sensing channel form a second difference during each of the first periods and each of the second periods, and in the step of generating the first difference, the second differences are integrated and amplified to output the first difference.