HD66789 Datasheet, PDF (114/156 Pages) Renesas Technology Corp – 528-channel, One-chip Driver for Amorphous TFT Panels with 262,144-color display RAM, Power Supply Circuit, and Gate Circuit

HD66789
Preliminary
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 grayscale voltage characteristics. Each
register can make an independent setting for the positive/negative polarity. The reference value and RGB
are common to both polarities.
Grayscale number
Gradient adjustment
Grayscale number
Amplitude adjustment
Grayscale 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 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 resistors (VRP(N)1/0) in the bottom 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, 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 fine-adjustment registers also incorporate separate registers
for positive and negative polarities.
Rev.0.12, May 09 2003, page 114 of 156