A 6.3 mW high-SNR frame-rate scalable touch screen panel readout IC with column-parallel Σ-Δ ADC structure for mobile devices

Abstract

This paper presents a capacitive touch screen panel (TSP) readout IC that provides highly enhanced signal-to-noise ratio (SNR) and scalable frame rate. To increase touch sensitivity and noise immunity, the proposed readout IC employs a differential sensing method. A column-parallel incremental sigma-delta (Σ-Δ) ADC structure is adopted to obtain high frame rate and its scalability. The readout IC is fabricated in 0.18-μm CMOS process and its active area is 2.2 mm2. The measured results show that the readout IC achieves 60-dB SNR and 200-Hz frame rate with 12 × 8 mutual capacitive TSP. The frame rate and SNR can be adjusted from 50 Hz to 1.6 kHz and from 50 dB to 67 dB, respectively. The power consumption is 6.3 mW with 3.3-V supply.