參數(shù)資料
型號(hào): HD66421
廠商: Hitachi,Ltd.
英文描述: (RAM-Provided 160 Channel 4-Level Grey Scale Driver for Dot Matrix Graphics LCD)
中文描述: (內(nèi)存提供160通道4級(jí)灰度的點(diǎn)陣圖形液晶顯示驅(qū)動(dòng)程序)
文件頁數(shù): 33/46頁
文件大?。?/td> 201K
代理商: HD66421
Preliminary
Rev. 1.1E '99.02.10
HD66421
Power Supply Circuits
HD66421 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 are
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 HD66421
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;
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;
1/8 bias
0.73 * (VLCD-GND)
VLCD
0.988 * (VLCD-GND)
1/9 bias
0.82 * (VLCD-GND)
VLCD
0.993 * (VLCD-GND)
(Example 1.)
1/11 bias
0.79 * (VLCD-GND)
VLCD
0.992 * (VLCD-GND)
Partial Display
0.82 * (Vcc-GND)
VCC
0.997 * (VCC-GND)
(Example 2.)
Partail display function uses 1/4 bias ratio from
VCC to GND. 8 levels of contrast can be selected
with data bit 2 to 0 of R16.
33
Vcc
IREFMP > IREFM
GND
VLCD > Vcc > GREF
GND
VLCD
V1O
V2O
V3O
V4O
V5O
GREF
GND
VLCD-Vcc
1.0V
IREFP-IREFM
1.0V
Vcc-GREF
1.0V
Example.1 LCD bias level
1/80 duty Display(1/9 bias, VLCD=12V,GND=0V)
Example 2. LCD bias level
Partial Display(1/4 bias,VCC=5V,GND=0V)
0
1
2
3
4
5
6
7
8
9
10
11
12
Contrast (R16)
V
V1O
V2O
V3O
V4O
V5O
0
1F
7
F
17
0
1
2
3
4
5
Contrast (R16)
V
V1O
V2O
V3O
V4O
V5O
0
7
4
(maximum)
(maximum)
VLCD
VCC
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