HD66781 Datasheet, PDF (160/196 Pages) Renesas Technology Corp – 720-channel Source Driver for a-Si TFT/Low Temperature Poly-Si TFT Panels with 262,144-color display RAM

HD66781
Preliminary
γ-Correction Registers
The γ-adjustment register is a group of registers to set an appropriate grayscale voltage for the γ-
characteristics of a liquid crystal panel. The register group is categorized into the ones adjusting gradient,
amplitude, and reference value and fine-tuning in relation to grayscale number and grayscale voltage
characteristics. Each register group can make an independent setting for the positive/negative polarity.
The reference value and RGB are common to both polarities.
Gray-scale number
Gradient
adjustment
Gray-scale number
Amplitude
adjustment
Gray-scale number
Fine adjustment
Gradient, Amplitude, Fine Adjustments
1. Gradient adjustment registers
The gradient adjustment registers are used to adjust the gradient around the middle of the grayscale number
and voltage characteristics without changing a dynamic range. To adjust a gradient, the values of the
variable resistors (VRHP (N)/VRLP (N)) in the ladder resistor block for grayscale voltage generation are
controlled. The registers incorporate separate registers for positive and negative polarities to be compatible
with asymmetric drive.
2. Amplitude adjustment registers
The amplitude adjustment registers are used to adjust the amplitude of the grayscale voltage. To adjust the
amplitude, the values of the variable resistors (VRP(N)1/0) in the upper and lower parts of the ladder
resistor block for grayscale voltage generation are adjusted. Same with the gradient registers, the amplitude
adjustment registers also incorporate separate registers for positive and negative polarities.
3. Fine adjustment registers
The fine adjustment register is to fine-adjust the grayscale voltage level. To fine-adjust the grayscale
voltage level, 8-to-1 selectors control each level of 8-level reference voltages generated from the ladder
registers. Same with the other registers, the fine adjustment registers also incorporate separate registers for
positive and negative polarities.
Rev.0.5, July.31.2003, page 160 of 196