A Fully-Differential Correlated Doubling Sampling Readout Circuit for Mutual-capacitance Touch Screens

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JSTS:Journal of Semiconductor Technology and Science, ISSN: 1598-1657, Vol: 15, Issue: 3, Page: 349-355

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Kwon, Kihyun; Kim, Sung Woo; Bien, Franklin; Kim, Jae Joon
The Institute of Electronics Engineers of Korea; IEEK PUBLICATION CENTER
Materials Science; Engineering; Sensor interface, readout circuit, Touch screen, differential, mutual capacitance
article description
A fully-differential touch-screen sensing architecture is presented to improve noise immunity and also support most multi-touch events minimizing the number of amplifiers and their silicon area. A correlated double sampling function is incorporated to reduce DC offset and low-frequency noises, and a stabilizer circuit is also embedded to minimize inherent transient fluctuations. A prototype of the proposed readout circuit was fabricated in a 0.18 mm CMOS process and its differential operation in response to various touch events was experimentally verified. With a 3.3 V supply, the current dissipation was 3.4 mA at normal operation and 140 mA in standby mode.