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18 LCD DRIVER (LCD24A)
18.4.2 External Voltage Application Mode 1
In this mode, all the LCD drive voltages V
voltage application mode 1, set both the LCD24PWR.VCEN and LCD24PWR.BSTEN bits to 0 to turn both the
LCD voltage regulator and LCD voltage booster off. Figure 18.4.2.1 shows an external connection example for ex-
ternal voltage application mode 1.
C
P4
C
P3
C
P2
C
P1
V
C4
V
C3
V
C2
V
C1
When 1/3 bias is selected (LCD24PWR.BISEL bit = 0)
Figure 18.4.2.1 External Connection Example for External Voltage Application Mode 1 (resistor divider)
18.4.3 External Voltage Application Mode 2
In this mode, the LCD drive voltage V
generated. To put LCD24A into external voltage application mode 2, set the LCD24PWR.VCEN bit to 0 to turn the
LCD voltage regulator off and the LCD24PWR.BSTEN bit to 1 to turn the LCD voltage booster on. Figure 18.4.3.1
shows an external connection example for external voltage application mode 2.
C
P4
C
P3
C
P2
C
P1
V
C4
V
C3
V
C2
V
C1
When 1/3 bias is selected (LCD24PWR.BISEL bit = 0)
Figure 18.4.3.1 External Connection Example for External Voltage Application Mode 2 (when V
18.4.4 LCD Voltage Regulator Settings
When using internal generation mode, select the reference voltage for boosting voltage generated by the LCD volt-
age regulator according to the power supply voltage V
"Electrical Characteristics" chapter and set the LCD24PWR.VCSEL bit. Current consumption can be reduced by
selecting reference voltage V
By setting the LCD24PWR.HVLD bit to 1, the LCD voltage regulator enters heavy load protection mode and en-
sures stable V
to V
outputs. Heavy load protection mode should be set when the display has inconsistencies in
C1
C4
density. Current consumption increases in heavy load protection mode, therefore do not set heavy load protection
mode if unnecessary.
18.4.5 LCD Voltage Booster Setting
Set the booster clock frequency used in the LCD voltage booster using the LCD24TIM2.BSTC[1:0] bits. Set it to
the frequency that provides the best V
18-6
to V
are applied from outside the IC. To put LCD24A into external
C1
C4
Open
R
LCD3
R
LCD2
R
LCD1
or V
is applied from outside the IC and other voltages are internally
C1
C2
Open
C
LCD5
C
C
LCD2
LCD3
DD
as compared with reference voltage V
C2
–V
output stability after being evaluated using the actual circuit board.
C1
C4
Seiko Epson Corporation
C
P4
C
P3
C
P2
C
P1
V
C4
V
C3
V
C2
V
C1
When 1/4 bias is selected (LCD24PWR.BISEL bit = 1)
C
P4
C
C
P3
C
P2
C
C
P1
V
C4
V
C3
V
C2
V
C1
When 1/4 bias is selected (LCD24PWR.BISEL bit = 1)
. Refer to "LCD Driver (LCD24A) Characteristics" in the
.
C1
S1C17W22/W23 TECHNICAL MANUAL
Open
R
LCD4
R
LCD3
R
LCD2
R
LCD1
LCD6
LCD5
C
C
C
LCD2
LCD3
LCD4
is applied)
C1
(Rev. 1.3)
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