A 32-dB SNR Readout IC with 20-Vpp Tx Using On-Chip DM-TISM in HV BCD Process for Mutual-Capacitive Fingerprint Sensor

This paper presents a readout IC with a 20 V high-voltage (HV) transmitter (Tx) and On-Chip Differentially Modulated Time-Interleaved Sensing Method (DM-TISM) in a BCD process for a mutualcapacitive Transparent Fingerprint Sensor (TFPS) in order to achieve high SNR, AC & DC offset reduction, high noise immunity, and compensate for the signal loss under thick cover glass. A proposed readout IC with on-chip DM-TISM is composed of 42 identical HV Tx channels, 32 identical Rx channels, and a diamond-patterned TFPS. The performance results including those for transient noise show that the DM-TISM achieves greater SNR than conventional TISM. The measured raw data show that the proposed readout IC achieves SNR of 32 dB with current consumption of 25 mA for the Tx and 13 mA for the Rx. It can be applied to any type of mobile device that needs fingerprint recognition. The ICs for the Tx and Rx are fabricated using 0.25-μm BCD process and 0.18-μm CMOS process with 1.6 mm × 3.5 mm and 2.5 mm × 2.5 mm areas, respectively.