Patent ID: 8188754

Claim:
A capacitance sensing device comprising: a. a sensed capacitor; b. a signal generator configured to generate a digital local oscillator signal and an excitation signal; c. a capacitance-to-amplitude converter coupled to the sensed capacitor and to the signal generator, wherein the capacitance-to-amplitude converter is configured to convert a measured capacitance received from the sensed capacitor to an AC signal according to the excitation signal, the AC signal having an amplitude proportional to the measured capacitance; d. a demodulator coupled to the capacitance-to-amplitude converter to receive the AC signal and to the signal generator to receive the digital local oscillator signal, wherein the demodulator is configured to output a DC component proportional to the AC signal and to output an AC component; and e. an analog-to-digital converter coupled to the output of the demodulator, wherein the analog-to-digital converter is configured to output a digital conversion value proportional to the DC component, which is proportional to the measured capacitance.