Improved SNR, On-Chip Differentially Modulated TISM Signaling in HV DMOS Process for Mutual Capacitance Fingerprint Sensor

Abstract

We propose improved SNR through on-chip Differentially Modulated Signaling with High Voltage (HV) based on Time-Interleaved Sensing Method (TISM) in fingerprint sensing. Tx driver transmits the 0 to 20V-pulse output with proposed signaling into Fingerprint Sensor (FPS), in order to increase the signal to noise ratio (SNR). When capacitance difference of valley-ridge is 0.4fF, the proposed differentially modulated TISM (DM-TISM) signaling is achieved to greater SNR (3.3dB) than that of conventional TISM in performance of fingerprint sensor readout IC architecture, when noise transient is included. Tx driver consists of 4 identical channels. A chip size is 1.3 × 1.1 mm 2 and prototype is fabricated in 0.25-um BCDMOS process.