A fully-differential capacitive touch controller with input common-mode feedback for symmetric display noise cancellation

A fully-differential capacitive touch sensing method is proposed in which common-mode noise currents are symmetrically subtracted at the differential input of the first stage such that it doesn't contribute to dynamic range reduction in the later stages. And, for better sensitivity, the proposed method could accumulate signal charges in continuous time domain, and does not suffer from aliasing issues observed in many discrete-time charge integrating methods. Measurement results showed 42 dB SNR for a 1-mm diameter stylus on a 5-inch full-HD on-cell touch display panel.