Small-Area and High-Accuracy Calibration Technique for Sensing Capacitor in the Touch Screen Panel

摘要

In this paper, a small-area and high-accuracy calibration technique for sensing capacitor in the touch screen panel is proposed. It uses 10-bit C-2C structure in calibration analog-to-digital converter (ADC) to get higher accuracy and small area just in one frame time. By boosting and comparing, the varied outputs of the charge amplifier are held at a reference voltage. Compared to previous calibration technique that adjusts feedback capacitor of the charge amplifier, it has advantage of faster speed, smaller area and higher accuracy. Simulation result shows that 10% variation of the sensing capacitance causes the variation of the output of charge amplifier less than 3mV in 3.5 inch touch screen panel.