Low-noise self-capacitor sensing for capacitive touch panels

Abstract

Techniques are described for low-noise self-capacitor sensing in a capacitive touch panel array integrated with a display panel. Each channel of the array has a self-capacitance (Ci) that changes responsive to presence or absence of a local touch event local. Each channel is read by an analog front-end (AFE) by using a locally noise-suppressed discharge current for a discrete discharge time to discharge Ci to obtain a discharge voltage level that differs with presence or absence of the local touch event, and outputting a voltage output for the channel based on the discharge voltage level by passively mixing at least the discharge voltage level to produce a pair of up-converted channel signals, sampling the pair of up-converted channel signals to obtain a differential voltage sample, and amplifying the differential voltage sample to generate the Vout as indicating absence or presence of the touch event local to the channel.