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 generated 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. The charge integrators 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 configured to obtain digital touch signals by analog-to-digital converting the spatial-common-mode-processed signals, obtain a digital spatial common mode estimate by analog-to-digital converting the spatial common mode estimate, and obtain at least one digital resulting signal by combining at least one of the digital touch signals with the digital spatial common mode estimate.