High-SNR Capacitive Multi-Touch Sensing Technique for AMOLED Display Panels

A mutual-capacitive multi-touch sensing technique is presented, especially for ultra-thin active-matrix organic light-emitting diode (OLED) display panels. The proposed scheme recognizes touch positions by detecting LC oscillation frequency shift. The signal feedback to the common cathode electrode of OLEDs cancels out the effects of parasitic coupling capacitances. In addition, the ground-floating-based scanning method enables a multi-touch function. The proposed touch sensor was implemented in a 0.35-μm CMOS process. Simulations were performed in model of 3.97-in on-cell-type TSP with various noise signals gathered by actual measurements. The proposed sensing technique achieves 68.9- and 61.6-dB signal-to-noise ratios with 6- and 2-mm diameter metal pillars, respectively.