Avoiding noise frequency interference with binary phase pulse driving and CDS for capacitive TSP controller

Abstract

Noise frequency interference avoidance (NFIA) using binary phase pulse driving and correlated double sampling (CDS) circuit technique is applied to avoid the interference of noise signal in capacitive touch screen panel (TSP). The proposed analog front-end circuitry is composed of a charge transfer circuit and a two-stage cascaded CDS circuit. The purpose of the two-stage cascaded CDS circuit is to remove harmonic noise frequencies interfering with touched data in TSP. If the system detects that noise frequencies interfere with the touched data, the proposed NFIA technique can be applied. Our proposed methodology is implemented in a real TSP system using 0.13-µm CMOS process and the measured SNR is 46 dB with the scan rate of 120 Hz in 21.5 inch TSP.