Low noise capacitive sensor for multi-touch mobile handset´s applications

Author

Ko, Seunghoon ; Shin, Hyungcheol ; Lee, Jaemin ; Jang, Hongjae ; So, Byeong-Sheol ; Yun, Ilhyun ; Lee, Kwyro

Author_Institution

Dept. of Electr. Eng., Korea Adv. Inst. of Sci. & Technol., Daejeon, South Korea

fYear

2010

fDate

8-10 Nov. 2010

Firstpage

1

Lastpage

4

Abstract

Capacitive touch screen sensor, though it enables multi-touch recognition, has problems rejecting distributed noise such as LCD, RF and EMI interferences coupled to transparent ITO electrodes. This paper presents a capacitive sensor design for multiple channels at the X-Y crossing of ITO patterns on the LCD panel. Capacitance-to-Voltage converter (C-VC) with moving average and time interleaved scheme is proposed to reject noises and achieve high data-rate. Calibration algorithm is used to compensate the delay of each channel due to series RC of ITO pattern. The measured signal-to-noise ratio of the sensor is 24 dB at 65 Hz scanning frequency for 320 channels. The prototype IC is implemented in a 0.18 CMOS technology, while consuming 13 mW from 3.3 V and 6 mW from 1.8 V supply.

Keywords

CMOS integrated circuits; capacitive sensors; electromagnetic interference; liquid crystal displays; mobile handsets; touch sensitive screens; CMOS technology; EMI interference; LCD panel; RF interference; capacitance-to-voltage converter; capacitive touch screen sensor; frequency 65 Hz; low noise capacitive sensor; multitouch mobile handset; multitouch recognition; power 13 mW; power 6 mW; size 0.18 mum; transparent ITO electrodes; voltage 1.8 V; voltage 3.3 V; Calibration; Capacitance; Electrodes; Frequency measurement; Indium tin oxide; Signal to noise ratio;

fLanguage

English

Publisher

ieee

Conference_Titel

Solid State Circuits Conference (A-SSCC), 2010 IEEE Asian

Conference_Location

Beijing

Print_ISBN

978-1-4244-8300-6

Type

conf

DOI

10.1109/ASSCC.2010.5716570

Filename

5716570