72 dB SNR, 240 Hz Frame Rate Readout IC With Differential Continuous-Mode Parallel Architecture for Larger Touch-Screen Panel Applications

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IEEE Transactions on Circuits and Systems I: Regular Papers, ISSN: 1549-8328, Vol: 63, Issue: 7, Page: 960-971

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Heo, Sanghyun; Ma, Hyunggun; Song, Joohyeb; Park, Kyoungmin; Choi, Eun-Ho; Kim, Jae Joon; Bien, Franklin
Institute of Electrical and Electronics Engineers (IEEE); IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
Engineering; Capacitor sensor; common-mode feedback; differential sensing; parallel operation; touch screen panel
article description
This paper presents a mutual capacitive touch screen panel (TSP) readout IC (ROIC) with a differential continuous-mode parallel operation architecture (DCPA). The proposed architecture achieves a high product of signal-to-noise ratio (SNR) and frame rate, which is a requirement of ROIC for large-sized TSP. DCPA is accomplished by using the proposed differential sensing method with a parallel architecture in a continuous-mode. This architecture is implemented using a continuous-type transmitter for parallel signaling and a differential-architecture receiver. A continuous-type differential charge amplifier removes the common-mode noise component, and reduces the self-noise by the band-pass filtering effect of the continuous-mode charge amplifier. In addition, the differential parallel architecture cancels the timing skew problem caused by the continuous-mode parallel operation and effectively enhances the power spectrum density of the signal. The proposed ROIC was fabricated using a 0.18-μm CMOS process and occupied an active area of 1.25 mm. The proposed system achieved a 72 dB SNR and 240 Hz frame rate with a 32 channel TX by 10 channel RX mutual capacitive TSP. Moreover, the proposed differential-parallel architecture demonstrated higher immunity to lamp noise and display noise. The proposed system consumed 42.5 mW with a 3.3-V supply.