Capacitive-based touch apparatus and method therefor, with reduced interference

摘要

A touch-sensitive device that includes a touch surface circuit that facilitates a change in a coupling capacitance in response to a capacitance-altering touches occurring at the touch surface. The device includes a sense circuit that provides a signal, in response thereto, having transient portions for characterizing positive-going transitions towards an upper signal level and negative-going transitions towards a lower signal level. An amplification circuit is then used for amplifying and processing the signals, in response to the time-varying input parameters. The amplification circuit adjusts the gain for the transient portions relative to gain for portions of the response signals between the transient portions, and thereby suppresses RF interference, such as in the form of signal odd and/or even harmonics, to provide a noise filtered output for determining positions of capacitance-altering touches on the touch surface.