HD66773R Datasheet, PDF (105/133 Pages) Renesas Technology Corp – 262,144-color, 132 x 176-dot Graphics Controller Driver for TFT LCD panels

HD66773R
Frame-Frequency Adjustment Function
The HD66773R incorporates frame frequency adjustment function. The frame frequency during the liquid
crystal drive is adjusted by the instruction setting (DIV, RTN) while keeping the oscillation frequency fixed.
Setting the oscillation frequency high in advance allows switching the frame frequency in accordance to the
kind of picture to be displayed (i.e. moving/still picture). When displaying a still picture, set the frame
frequency low to save power consumption, while setting the frame frequency high for displaying a moving
picture which requires high-speed switching of screens.
Relationship between Liquid Crystal Drive Duty and Frame Frequency
The relationship between the liquid crystal drive duty and the frame frequency is calculated by the
following formula. The frame frequency is adjusted through instruction setting with the 1-H period
adjustment bit (RTN bit) and the operation clock division bit (DIV bit).
(Formula for the frame frequency)
fosc
Frame frequency =
[Hz]
Clock cycles per raster-row × division ratio × (Line+8)
fosc: R-C oscillation frequency
Line: number of drive raster-rows (NL bit)
Clock cycles per raster-row: RTN bit
Division ratio: DIV bit
Calculation Example The maximum frame frequency = 60 Hz
Number of drive raster-rows: 176
1-H period: 16 clock cycles (RTN3-0 = 0000)
Operation clock division ratio: 1 division
fosc = 60 Hz × (0 + 16) clock × 1 division × (176 + 8) lines = 177 (kHz)
In this case, the R-C oscillation frequency becomes 177 kHz. Adjust the resistance of external resistor for
the R-C oscillator to177 kHz.
Rev.1.10, Jun.21.2003, page 105 of 133