Synaptics Incorporated
Capacitive sensing device with single reference channel

Abstract:

An example a processing system for a capacitive sensing device includes a reference transmitter coupled to a reference capacitance. The processing system further includes a charge accumulation circuit having an input coupled to the reference transmitter through the reference capacitance and configured to generate an integrated signal, a demodulator circuit having an input coupled to an output of the charge accumulation circuit and configured to demodulate the integrated signal to generate at least one demodulated signal, a sampling circuit having an input coupled to an output of the demodulator circuit and configured to sample the demodulated signal(s), a first reference buffer coupled to an output of the sampling circuit, the first reference buffer outputting a first voltage reference for the capacitive sensing device, and a second reference buffer coupled to the output of the sampling circuit, the second reference buffer outputting a second voltage reference for the capacitive sensing device.