Synaptics Incorporated
Common mode noise suppression with restoration of common mode signal

Abstract:

A processing system is disclosed. The processing system includes an amplifier configured to generate a feedback signal including a spatial common mode estimate from spatial-common-mode-processed signals. The processing system further includes charge integrators configured to obtain resulting signals from capacitive sensor electrodes, the resulting signals including a spatial common mode, and generate the spatial-common-mode-processed signals by mitigating the spatial common mode in the resulting signals using the feedback signal. The processing system also includes a controller including a programmable gain amplifier capturing the spatial common mode estimate over a summing resistor of the amplifier and a demodulator configured to remove a modulation voltage from the spatial common mode estimate.