Capacitor Reused Gate Driver for Compact In-Cell Touch Displays

Abstract

A thin-film transistor (TFT) integrated gate driver is proposed for compact in-cell touch display, where one capacitor is reused for both turning on low-level maintaining transistors via voltage coupling and maintaining the re-start charge during the touch sensing period. The gate terminal of buffer transistor is thus free of electrical stress during touch sensing period, and can be re-charged for the subsequent re-start period, leading to minimal variations in the transient response. With the capacitor reusing scheme and a capacitor stacking structure, the area of the single stage gate driver is decreased to $645\,\,\mu \text{m}\,\,\times 210\,\,\mu \text{m}$ . The fabricated a-Si TFT gate driver with 8 cascaded stages shows that the rising and falling time variations among re-start and normal gate driver stages are less than $1~\mu \text{s}$ . Versatile touch sensing modes and bidirectional scanning functions are verified.

Keywords

• Capacitor reusing
• gate driver
• in-cell touch
• bidirectional scanning
• display