DOI QR코드

DOI QR Code

Capacitive Touch Switch Regardless of Operating Frequency Using a Switched-Capacitor

스위치드 커패시터를 이용한 동작 주파수에 무관한 정전용량 터치스위치

  • Lee, Mu-Jin (Department of Electronic Engineering, Yengnam University) ;
  • Seong, Kwang-Su (Department of Electronic Engineering, Yengnam University)
  • 이무진 (영남대학교 전자공학과) ;
  • 성광수 (영남대학교 전자공학과)
  • Received : 2013.04.06
  • Accepted : 2013.05.14
  • Published : 2013.06.30

Abstract

This paper proposes a capacitive touch switch using a switched-capacitor. The proposed method charges capacitance for measurement using the switched-capacitor until the voltage across the capacitance reaches a threshold voltage. As the proposed method uses the number of times being charged to measure the capacitance, the method has no relation with the operating frequency of the switched-capacitor. This paper also shows the quantization resolution of the proposed method is related to the capacitance in the switched-capacitor and the threshold voltage, i.e., the resolution is improved when the capacitance in the switched-capacitor is decreased and the threshold voltage is increased. Simulation result shows the method gives 31fF quantization resolution when the capacitance in the switched-capacitor is 50fF and threshold voltage is 80% of the supply voltage.

Keywords

References

  1. Kwang-Su Seong, "An efficient pulse width measurement method using multiphase clock signals for capacitive touch switches," Journal of Electrical Engineering & Technology, (accepted for publication).
  2. Kwang-Su Seong, "A design of full digital capacitive sensing touch key reducing the effects due to the variations of resistance and clock frequency,"Journal of the Korean Institute of Illuminating and Electrical Installation Engineers, Vol.23, No.4, pp.39-46, Apr.2009. https://doi.org/10.5207/JIEIE.2009.23.4.039
  3. Chul Nam, Young-Gun Pu, and Kang-Yoon Lee, "$12{\times}12$ capacitive matrix touch sensing unit for SoC application in 0.18um CMOS process," 2009 International SoC design conference (ISOCC),pp.305-308,Nov.2009.
  4. Microchip Technology Inc., "40/44-pin, flash microcontrollers with nanoWattXLP and mTouch technology, PIC16(L)F707," 2011.
  5. Nils Karlsson, "A study of a high-resolution linear circuit for capacitive sensors," IEEE Trans. on Instrumentation and Measurement, vol.48, no.6, pp.1122-1124, Dec.1999. https://doi.org/10.1109/19.816125
  6. Seunghoon Ko, Hyungcheol Shin, Jaemion Lee, Hongjae Jang, Byeong Cheol So, Ilhyun Yun, and Kwyro Lee, "Low noise capacitive sensor for multiple-touch mobile handset's applications," 2010 IEEE Asian Solid-State circuits conference, pp.1-4, Nov.2010.
  7. Manel Gasulla, "The noise performance of a high-speed capacitive-sensor interface based on a relaxation oscillator and a fast counter," IEEE Trans. on Instrumentation and Measurement, vol.54, no.5, pp.1934-1940, Oct.2005. https://doi.org/10.1109/TIM.2005.853684
  8. Wikipedia - The free encyclopedia, "Switched capacitor," available on http://www.wikipedia.org.