A Highly Noise-Immune Capacitive Touch Sensing System Using an Adaptive Chopper Stabilization Method

Abstract

This paper proposes a capacitive touch sensing system (CTSS) using an adaptive chopper stabilization (ACS) method to achieve high noise immunity. The proposed ACS method quickly detects and adaptively filters out external noises, thereby achieving high noise immunity in the proposed CTSS. To verify the proposed ACS method, a readout integrated circuit (ROIC) was fabricated using a 0.35-mu m CMOS process technology with 18 V high-voltage devices and was measured using a 46-in capacitive touch sensor (CTS). When no external noises are induced into the CTS, the measured signal-to-noise ratio (SNR) of the ROIC is 45.8 dB at a reporting rate of 120 Hz. When external noises are induced into the CTS, the measured SNR of the ROIC using the ACS method is 44.5 dB, which is improved by 22.0 dB compared with the SNR achieved without using the ACS method. Therefore, the proposed ACS method effectively eliminates external noises induced into the CTS of the CTSS.