A switched-capacitor differential-capacitance-to-time converter for capacitive sensors

A high-accuracy and low-power consumption switched-capacitor (SC) differential-capacitance-to-time converter (DCTC) is presented for high-accuracy ratiometric operation of capacitive sensors. This circuit does not require additional capacitors and component matching. Performances of the proposed circuit are simulated by HSPICE using a 0.35 μm n-well CMOS process parameter. Simulated results have demonstrated that the capacitance difference can be linearly converted to time. A prototype circuit built using discrete components has confirmed the principles of operation.