11.7 A load-aware pre-emphasis column driver with 27% settling-time reduction in ±18% panel-load RC delay variation for 240Hz UHD flat-panel displays (2016)

In this paper, we present a column driver with load-aware pre-emphasis driving (LPD) as in Fig. 11.7.2. The LPD scheme calibrates the K value to the panel-load resistance and capacitance to minimize the increase in the settling time due to the column-to-column and panel-to-panel R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> delay variation. In addition, the self K-calibration reduces fabrication cost because no trimming of the K is required during fabrication. Before the column driver starts its data-driving operation, a K-calibrator embedded in every column searches the K corresponding to the panel load R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> and C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> of each column and adjusts the K of a pre-emphasis voltage generator (PVG). The K-calibration searches for the K value where the voltage buffer supplies a proper amount of charge for the voltage step (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">REF2</sub> -V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">REF1</sub> ) to the panel load capacitance C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> during the preemphasis duration T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">PRE</sub> . To measure the amount of charge on C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> , the data line is detached from the voltage buffer after T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">PRE</sub> (φ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DRV</sub> = L) so that the charges on the data line are redistributed. After enough time elapses, the nodes on the data line (v <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1,2,...,N</sub> ) are stabilized to one voltage, which is compared to the target data voltage (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">REF2</sub> ). When there is an error, the K-calibrator adjusts the K value to make the data line voltage close to the target data voltage V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> . For more precise matching between the amount of the injected charge of the K-calibration and a real driving, the data lines can be disconnected a few hundred nanoseconds after T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">PRE</sub> to reflect the charge leaked during the pre-emphasized output v <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">O</sub> slewing down to V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">REF2</sub> .