參數(shù)資料
型號: HD66420TA0
廠商: Hitachi,Ltd.
英文描述: LCD Display Driver
中文描述: 液晶顯示驅(qū)動程序
文件頁數(shù): 38/52頁
文件大小: 167K
代理商: HD66420TA0
HD66420
38
Power Supply Circuits
HD66420 has following circuits for power supply circuit: operational amplifiers, resistive dividers, bias
control circuit and contrast control circuit. LCD driving voltage, VLCD, must be generated externally.
LCD Drive Voltage Power Supply Levels:
To drive the LCD, a 6-level power supply is necessary. These
levels are generated internally or supplied from outside. When an internal voltage levels generator is
chosen, external capacitors are needed to stabilize these levels. AS the HD66420 incorporates operational
amplifiers to these levels, this circuit gives better quality of display with less power consumption. This
divided ratio is programmable.
Bias current of internal operational amplifier is determined with a resister which is inserted between
IREFM and GND. This resister value is between 1M
and 5M
. Larger resister value make less power
consumption at internal operational amplifier. However, too large value loose operational margin of
amplifiers.
Keep following relationship among voltage levels;
V
CC
IREFMP > IREFM
GND
VLCD > V
CC
> GREF
GND
VLCD
V1O
V2O
V3O
V4O
V5O
GREF
VLCD–V
CC
1.0V
IREFP–IREFM
1.0V
V
CC
–GREF
1.0V
Contrast Control:
Internal contrast control circuit can change the output voltage level of VLCD by setting
data to contrast control register, R16. VLCD adjustable range are showed below;
1/6 bias
0.75 * (VLCD-GND)
VLCD
0.99 * (VLCD-GND)
1/9 bias
0.82 * (VLCD-GND)
VLCD
0.993 * (VLCD-GND)
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