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.
Highlights
Gate driver circuit integration using thin-film transistors (TFTs) becomes important for the-state-of-the-art active matrix displays
The electrical characteristics of discrete aSi:H TFT samples are measured with Keithley 4200
In the touch sensing and re-start periods, there are two touch detection intervals with duration of 100 μs, one placed between the 2nd and 3rd pulse waveforms, and the other located between the 5-th and 6-th pulse waveforms. These results prove that the touch detection intervals can be flexibly arranged between the adjacent gate driver stages, by changing the turning sequence of TP and RCK signals
Summary
Gate driver circuit integration using thin-film transistors (TFTs) becomes important for the-state-of-the-art active matrix displays. For the in-cell touch display, discontinuous row scanning pulses are required [5] This is because gate driver output should be maintained with low voltage (i.e., VL), during touch sensing periods, to minimize interferences from display driving signals. Moon et al demonstrated the first type gate driver, where the re-start charge is maintained by the gate electrode of buffer transistor, i.e., the main transistor with large width-to-length ratio for pullingup and pulling-down the voltage level of loading capacitor and resistors of gate lines [7]. It is not easy to implement TFT integrated gate driver with both bi-directional scanning and re-start charge maintaining functions for in-cell touch display [11]–[13]. Transient performances of fabricated circuit samples will be characterized through measurements at the final part
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