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An Excessive Current Subtraction Technique to Improve Dynamic Range for Touch Screen Panel Applications
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 Title & Authors
An Excessive Current Subtraction Technique to Improve Dynamic Range for Touch Screen Panel Applications
Heo, Sanghyun; Ma, Hyunggun; Bien, Franklin;
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A current subtraction technique with parallel operation system is proposed to remove excessive current in touch screen application. The proposed current subtraction remove the current which go into the input node of charge amplifier. The value of subtraction current is same with current when touch screen is not touched. As a result, charge amplifier output is only proportional to variation of mutual capacitor, which make dynamic rage is increased. Also, Transmitter (Tx) driving signal and subtraction driving signal are out of phase each other. Thus, noise generated in Tx is cancelled. The proposed IC is implemented in a mixed-mode 0.18-um CMOS process. Overall system is designed for touch screen panel (TSP) with 16 driving lines and 8 sensing lines. 5-V supply voltages are used in the proposed circuits. For multiple Tx driving signal, Walsh codes are used and signal frequency is 300 khz. By using proposed technique, dynamic rage is improved 36 dB.
Touch screen;high voltage;parallel operation;current subtraction;
 Cited by
Sanghyun Heo, et al "Dynamic range enhanced readout circuit for a capacitive touch screen panel with current subtraction technique," European Solid State Circuits Conference (ESSCIRC), ESSCIRC 2014 - 40th, vol., no., pp.327,330, 22-26 Sept. 2014

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Ko, Seunghoon, et al. "A 70dB SNR capacitive touch screen panel readout IC using capacitor-less trans-impedance amplifier and coded Orthogonal Frequency-Division Multiple Sensing scheme." VLSI Circuits (VLSIC), 2013 Symposium on. IEEE, 2013.

Ma, Hyunggun, et al. "Algorithm for improving SNR using high voltage and differential Manchester code for capacitive touch screen panel." Electronics Letters 50.24 (2014): 1813-1815. crossref(new window)