In this letter, we evaluate the parasitic capacitance of an LCD touch panel, the description and implementation of a differential input sensing circuit, and an algorithm suitable for large LCDs with integrated touch function. When projected capacitive touch sensors are integrated with a liquid crystal display, the sensors have a very large amount of parasitic capacitance with the display elements. A differential input sensing circuit can detect small changes in the mutual capacitance from the touch of a finger. The circuit is realized using discrete components, and for the evaluation of a large-sized LCD touch panel, a printed circuit board touch panel is used.

For a large-sized touch screen, we designed and evaluated a real-time touch microarchitecture using a field-programmable gate array (FPGA). A high-speed hardware accelerator based on a parallel touch algorithm is suggested and implemented in this letter. The touch controller also has a timing control unit and an analog digital convert (ADC) control unit for analog touch sensing circuits. Measurement results of processing time showed that the touch controller with its proposed microarchitecture is five times faster than the 32-bit reduced instruction set computer (RISC) processor without the touch accelerator.