11.6 A 100-TRX-channel configurable 85-to-385Hz-frame-rate analog front-end for touch controller with highly enhanced noise immunity of 20Vpp

Touch screens have recently been adopted not only for smartphones but also for tablet PCs and home appliances that have touch-screen panels (TSPs) larger than 10 inches. However, there are many sources of noise that affect touch detection, and some of these noise sources, such as charger noise, significantly affect the capacitance variation needed to detect touch input and lead to inaccurate touch detection [1-2]. For example, as shown in Fig. 11.6.1, common-mode supply noise results in large peak-to-peak noise injection over 10Vpp and deteriorates touch-detection performance. Although rejection of display noise using the differential sensing method [3] has been investigated, sufficient attenuation of the injected noise through a touch object remains a problem. In this paper, we present an analog front-end (AFE) with noise immunity of up to 20Vpp for a large TSP controller. To improve the immunity to the injected noise, the proposed AFE employs the following techniques: a) TX/RX dual modulation, b) differential sensing, c) high-order noise filtering, and d) multiple TX driving frequency support. Further, to cope with various usages and advanced touch-detection modes, the proposed AFE provides a configurable frame rate from 85 to 385Hz.

[1]  Deog-Kyoon Jeong,et al.  A Reconfigurable 40-to-67 dB SNR, 50-to-6400 Hz Frame-Rate, Column-Parallel Readout IC for Capacitive Touch-Screen Panels , 2014, IEEE Journal of Solid-State Circuits.

[2]  Gyu-Hyeong Cho,et al.  A highly noise-immune touch controller using Filtered-Delta-Integration and a charge-interpolation technique for 10.1-inch capacitive touch-screen panels , 2013, 2013 IEEE International Solid-State Circuits Conference Digest of Technical Papers.

[3]  Sungsoo Park,et al.  6.8 A pen-pressure-sensitive capacitive touch system using electrically coupled resonance pen , 2015, 2015 IEEE International Solid-State Circuits Conference - (ISSCC) Digest of Technical Papers.

[4]  Sungsoo Park,et al.  A Pen-Pressure-Sensitive Capacitive Touch System Using Electrically Coupled Resonance Pen , 2016, IEEE Journal of Solid-State Circuits.

[5]  Masayuki Miyamoto,et al.  6.6 A 240Hz-reporting-rate mutual-capacitance touch-sensing analog front-end enabling multiple active/passive styluses with 41dB/32dB SNR for 0.5mm diameter , 2015, 2015 IEEE International Solid-State Circuits Conference - (ISSCC) Digest of Technical Papers.

[6]  Masayuki Miyamoto,et al.  12.3 A 240Hz-reporting-rate 143×81 mutual-capacitance touch-sensing analog front-end IC with 37dB SNR for 1mm-diameter stylus , 2014, 2014 IEEE International Solid-State Circuits Conference Digest of Technical Papers (ISSCC).

[7]  Hyungcheol Shin,et al.  A 55dB SNR with 240Hz frame scan rate mutual capacitor 30×24 touch-screen panel read-out IC using code-division multiple sensing technique , 2013, 2013 IEEE International Solid-State Circuits Conference Digest of Technical Papers.