The critical issues in charge-based touch screen panels for large size display are noise and speed. To solve these, this paper introduces a two-point relative sensing based ‘Delta-Integration’ scheme. It eliminates local noise and increases a readout difference between the touched and non-touched area. As a result, it can replace a high-resolution ADC with a comparator and counter. In addition, the single-bit conversion of Δ-integration method and the proposed wide-bandwidth charge amplifier solve a speed issue of a large display. The prototype chip is implemented in a 0.35-µm CMOS technology.
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