HD66773R Datasheet, PDF (87/133 Pages) Renesas Technology Corp – 262,144-color, 132 x 176-dot Graphics Controller Driver for TFT LCD panels

HD66773R
γ-Correction Register
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 fine-tuning in relation to grayscale number and voltage characteristics. Each register can
make an independent setting for the positive/negative polarity. The reference value and RGB are common
for all registers.
Grayscale Number
Gradient Adjustment
Grayscale Number
Amplitude Adjustment
Grayscale Number
Fine Adjustment
γ-Correction Register
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 the dynamic range. To adjust a gradient, the values of the
variable resistors (VRHP (N)/VRL (N)) in the middle of 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 resistor (VRP(N)1/0) located at the lower side of the ladder resistor
block for grayscale voltage generation are adjusted. The variable resistor located at the upper side of the
ladder resistor block is adjusted by the input VDH level or reference resistor. Same with the gradient
registers, the 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, each level of 8-level reference voltages generated from the ladder registers is controlled by 8-
to-1 selector. Same with the other registers, the registers also incorporate separate registers for positive and
negative polarities.
Rev.1.10, Jun.21.2003, page 87 of 133