Mutual Capacitive Sensing Touch Screen Controller for Ultrathin Display with Extended Signal Passband Using Negative Capacitance

Autor: Chang-Ju Lee, Jong Kang Park, Canxing Piao, Han-Eol Seo, Jaehyuk Choi, Jung-Hoon Chun
Jazyk: angličtina
Rok vydání: 2018
Předmět:
Zdroj: Sensors, Vol 18, Iss 11, p 3637 (2018)
Druh dokumentu: article
ISSN: 1424-8220
DOI: 10.3390/s18113637
Popis: Flexible and thin displays for smart devices have a large coupling capacitance between the sensor electrode of the touch screen panel (TSP) and the display electrode. This increased coupling capacitance limits the signal passband to less than 100 kHz, resulting in a significant reduction in the received signal, with a driving frequency of several hundred kilohertz used for noise avoidance. To overcome this problem, we reduced the effective capacitance at the analog front-end by connecting a circuit with a negative capacitance in parallel with the coupling capacitance of the TSP. In addition, the in-phase and quadrature demodulation scheme was used to address the phase fluctuation between the signal and the clock during demodulation. We fabricated a test chip using the 0.35 µm CMOS process and obtained a signal-to-noise ratio of 43.2 dB for a 6 mm diameter metal pillar touch input.
Databáze: Directory of Open Access Journals
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