Patent ID: 8339148

Claim:
A multi-channel capacitive sensing circuit comprising: at least one capacitive sensor having capacitance changed corresponding to the change of external environment and generating capacitance change signals corresponding to the capacitance change, respectively; an oscillator outputting a carrier wave modulating the capacitance change signal; at least one capacitance-to-voltage converter each receiving the capacitance change signals modulated by means of the carrier wave and outputting voltage signals corresponding to the modulated capacitance change signals, respectively; a multiplexer receiving the voltage signals and selecting any one of the voltage signals to sequentially output it; and an analog-to-digital converter (ADC) receiving the voltage signals outputted from the multiplexer, converting the voltage signals into digital voltage signals and outputting them, wherein each of the at least one capacitive sensor comprises a first capacitor and a second capacitor whose capacitances are changed by different amount with respect to the change of external environment, wherein the oscillator is electrically connected to the first and second capacitors and outputs the carrier wave to the first and the second capacitors, wherein the oscillator is a chopper oscillator, and further comprising an inverter electrically connected to the oscillator and the second capacitor, receiving the carrier wave, and outputting an anti-phase carrier wave having a phase opposite to that of the carrier wave.