Patent ID: 8536881

Claim:
A capacitance sensing circuit, driven at least by a driving signal having rising edges and falling edges, comprising: a difference comparing unit receiving a waveform under test and a reference waveform, wherein the difference comparing unit outputs a differential signal according to at least one positive edge difference and at least one negative edge difference between the waveform under test and the reference waveform, wherein the difference comparing unit has a first input end and a second input end, in at least one first period of a sensing period, the first input end receives the waveform under test, and the second input end receives the reference waveform, and in at least one second period of the sensing period, the first input end receives the reference waveform, and the second input end receives the waveform under test, and wherein the waveform under test and the reference waveform are positive pulses and negative pulses alternating changing respectively according to the rising edges and falling edges of the driving signal, so the at least one positive edge difference occurs at the rising edges and the at least one negative edge difference occurs at the falling edges.