Synaptics Incorporated
LOW GROUND MASS CORRECTION FOR CAPACITIVE IMAGING SENSORS

Abstract:

A capacitive sensing input system includes sensor electrodes disposed in a sensor electrode pattern and a processing system. When under a low ground mass (LGM) condition, proximity-sensing pairs of electrodes formed by a first selective pairing of the sensor electrodes have an increased sensitivity to a presence of an input object in comparison to LGM-sensitive pairs of electrodes formed by a second selective pairing of the sensor electrodes that are primarily sensitive to the LGM condition. The processing system is configured to, while under the LGM condition, determine a first LGM term using a mutual capacitance sensing with a first of the LGM-sensitive pairs of electrodes, obtain a first transcapacitance sensing signal for a sensing element formed by a first of the proximity-sensing pairs of electrodes, and generate an LGM-corrected transcapacitance sensing signal by correcting the first transcapacitance sensing signal using the first LGM term.