An analog front-end for self-capacitance touch sensing with environmental noise reduction technique

Abstract

A differential analog front-end (AFE) circuit for self-capacitance touch screen panel (TSP) is described. It receives two pseudo-differential signals from a panel to cancel out common environmental noises. Each pseudo-differential input signal is achieved by using up and down charge-pumps which convert self-capacitances of two adjacent channels into voltages. The dc signal resulted from the proposed capacitance-to-voltage converter is cancelled out by summing the two differential inputs which have opposite polarity dc levels. It enables the use of high gain amplifier which results in enhanced sensitivity.