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 cross-talk between display signals and touch signals. In the conventional gate driver circuit, transistors are connected between the gate node of pull-up transistor $Q$ node and the low DC supply voltage $V _{GL}$ to reset the $Q$ 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 $V _{GL}$ 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 $V _{GH}$ to keep the voltage at the $Q$ 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.