Title :
A 0.4 V driving multi-touch capacitive sensor with the driving signal frequency set to (n+0.5) times the inverse of the LCD VCOM noise period
Author :
Jae-Seung Lee ; Dong-Hee Yeo ; Sang-Soo Lee ; Hye-Jung Kwon ; Jae-Yoon Sim ; Byung-Sub Kim ; Hong June Park
Author_Institution :
Pohang Univ. of Sci. & Technol. (POSTECH), Pohang, South Korea
Abstract :
The time-periodic property of the LCD VCOM noise is utilized to reduce the effect of the VCOM noise on the mutual-capacitance measuring touch sensor placed on a LCD panel. The amplitude of the touch sensor driving signal (VSTM) can be reduced reliably down to 0.4 V with the reporting rate of 189 Hz, by using the following two methods. (1) The frequency of VSTM is set to (n+0.5)·fN, by synchronizing VSTM to a LCD gate driver signal with a referenceless CDR. fN is the inverse of the LCD VCOM noise period (TN) and n is a positive integer. (2) The reset period of the RX integrator is set to 2·TN.
Keywords :
capacitance measurement; capacitive sensors; driver circuits; liquid crystal displays; tactile sensors; CDR; LCD VCOM noise period; LCD gate driver signal; VSTM; driving signal frequency; frequency 189 Hz; multitouch capacitive sensor; mutual-capacitance measuring touch sensor; time-periodic property; touch sensor driving signal amplitude; voltage 0.4 V; Electrodes; Logic gates; Noise; Noise measurement; Semiconductor device measurement; Tactile sensors; Voltage measurement; VCOM noise; mutual-capacitance; touch sensor;
Conference_Titel :
Circuits and Systems (ISCAS), 2014 IEEE International Symposium on
Conference_Location :
Melbourne VIC
Print_ISBN :
978-1-4799-3431-7
DOI :
10.1109/ISCAS.2014.6865227
