Experimental characterization and methodology for full-wave modeling of ESD to displays

An electrostatic discharge (ESD) to the touchscreen display of a cellphone or other handheld device can result in device failures through sparkless discharge. A test model has been designed and a test board built to investigate sparkless discharge to glass displays, based on the discharge path in a typical product. The current waveform at the touchscreen circuit load was captured during an air discharge using an oscilloscope for 40 test cases with different glass thicknesses, load resistances, and patch-to-ground capacitances. Full wave and circuit models of the discharge event have also been developed. Using the circuit model and a genetic algorithm approach, methods were developed for estimating the input current waveform associated with the discharge event. Using this current waveform, it is possible to predict the magnitude, rise time, total charge, and energy of a typical surface discharges to displays during the early stages of product design to prevent device failures.