參數(shù)資料
型號: LH1554P
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): 23/51頁
文件大?。?/td> 288K
代理商: LH1554P
23
LH155BA
2.19. Voltage Control Circuit
The boosted voltage at the V
OUT
pin is connected
to the V
R1
and V
R2
pins and then the LCD drive
voltages (V
0
, V
1
, V
2
, V
3
, and V
4
) are generated via
the voltage converter. The input level at the V
R1
and V
R2
must meet the electric potential condition
of V
R1
≥ V
R2
. The internal electronic volume
divides the electric potential between the V
R1
and
V
R2
into 16 segments.
Since the V
R1
and V
R2
pins have high input
impedance, the input voltage levels at the V
R1
and
V
R2
are determined by the resistance ratio of R
1
,
R
2
, and R
3
. The current flowing between the V
OUT
and V
SS
pins is determined by the combined
resistance of R
1
, R
2
, and R
3
.
Therefore, R
1
, R
2
, and R
3
must be selected in
accordance with the above current as well as the
input voltage levels at the V
R1
and V
R2
.
The boosted voltage at the V
OUT
pin originates
from the voltage supplied at the V
EE
pin. Thus, the
DC path current generated with R
1
, R
2
, and R
3
connected between the V
OUT
and V
SS
pins is
supplied as current at the V
EE
pin. The electric
current value, four times larger than the DC path
current generated between the V
OUT
and V
SS
pins
when the voltage is boosted four times, is added as
supply current at the V
EE
pin (three times larger
current is added for tripled voltage). Take sufficient
care that the input levels at the V
R1
and V
R2
pins
do not fluctuate with external noise (connect
capacitor C
3
).
2.20. Electronic Volume
The voltage converter incorporates an electronic
volume, which allows the LCD drive voltage level
V
0
to be controlled with a command and also
allows the tone of LCD to be controlled.
If 4-bit data is stored in the register of the electronic
volume, one level can be selected among 16
voltage values for the LCD drive voltage V
0
. The
voltage control range of the electronic volume is
determined by the input voltage levels at the V
R1
and V
R2
. This means that the voltage range of (V
R1
to V
R2
) for the graphic display voltage control circuit
is the controllable voltage range of the electronic
volume. The electric potential relation between the
V
R1
and V
R2
pins must be V
R1
≥ V
R2
. The input
voltage levels at the V
R1
and V
R2
must be selected
in accordance with the voltage levels to be obtained
with the electronic volume.
2.21. LCD Drive Voltage Generation
Circuit
The voltage converter contains the voltage
generation circuit. The LCD drive voltages other
than V
0
, that is, V
1
, V
2
, V
3
and V
4
, are obtained by
dividing V
0
through a resistor network. The LCD
drive voltage from LH155BA is biased at 1/7 or 1/9
for the graphic display mode and at 1/3 (fixed) for
the segment display mode.
When using the internal power supply, connect a
stabilizing capacitor C
2
to each of pins V
0
to V
4
.
The capacitance of C
2
should be determined while
observing the LCD panel to be used. In this case,
connect a capacitor C
3
to stabilize input voltage to
V
R1
and V
R2
. A value of C
3
can be defined
selectively.
C
3
C
3
R
3
R
2
R
1
V
R1
V
OUT
LH155BA
V
R2
V
SS
C
1
Example of Voltage Control Circuit
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