A low-offset, low-noise, Fully Differential Receiver with a Differential Signaling Method for Fingerprint Mutual Capacitive Touch Screen

Abstract

This paper presents a fingerprint mutual capacitive touch-screen panel (TSP) readout IC (ROIC) with a differential signaling method for fast fingerprint recognition. A readout IC with high SNR and fast frame rate are required in the fingerprint recognition. However, the capacitance difference by the ridge and valley of the fingerprint is very small, so that the signal-to-noise ratio is very low. In addition, it takes long time to scan whole fingerprint TSP with multiple electrodes. A fully differential architecture with differential signaling is proposed to detect the low capacitance difference in fingerprint TSP. The internal noise generated is minimized by 2 nd fully differential operational amplifier and external noise is eliminated by a lock-in sensing structure. In addition, DCMS reduces an AC offset and enhances a higher product of SNR and frame rate in multiple channels. Proposed IC has been fabricated using a 0.18 μm standard CMOS process.