Highly Robust Integrated Gate-Driver for In-Cell Touch TFT-LCD Driven in Time Division Driving Method

Abstract

This paper proposes a gate driver circuit for in-cell touch thin-film transistor (TFT) liquid crystal displays (LCDs) in which display and touch are driven at separate times to avoid crosstalk between display signals and touch signals. In the conventional gate driver circuit, transistors are connected between the gate node of pull-up transistor node and the low DC supply voltage to reset the node. In the proposed gate driver gate driver circuit, these transistors are instead connected to the Touch Enable signal. During the display operation, the Touch Enable signal voltage is to operate the proposed gate driver circuit in the same way as the conventional circuit. During touch operations, the Touch Enable signal changes to the high DC supply voltage to keep the voltage at the node constant without leakage. In simulations and experiments, the proposed gate driver circuit prevented display failures caused by the interval during which the display pauses in the middle of a frame time for touch operation. The fabricated low temperature poly-silicon (LTPS) TFT-LCD has good multi-touch functionality without any ghost touches, and achieved 40-dB SNR and 120 Hz touch report rate.