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CHAPTER 17 LCD CONTROLLER/DRIVER
User
’
s Manual U14701EJ3V0UD
17.7 Supplying LCD Drive Voltages V
LC0
, V
LC1
, and V
LC2
The
μ
PD780338 contains a booster circuit (
×
3 only) to generate a supply voltage to drive the LCD. The internal
LCD reference voltage (V
LCD2
) is output from the V
LC2
pin. A voltage two times higher than that on V
LCD2
is output
from the V
LC1
pin and a voltage three times higher than that on V
LCD2
is output from the V
LC0
pin.
The LCD reference voltage (V
LCD2
) can be varied by connecting external resistors as shown in Figure 17-11.
In addition, the
μ
PD780338 requires an external capacitor (recommended value: 0.47
μ
F) because it employs a
capacitance division method to generate a supply voltage to drive the LCD.
Table 17-6. Output Voltages of V
LC0
to V
LC2
Pins
Output Voltage
V
LC0
pin
3
×
V
LCD2
V
LC1
pin
2
×
V
LCD2
V
LC2
pin
V
LCD2
Cautions 1. When using the LCD function, do not open the V
LCDC
, V
LC0
, V
LC1
, and V
LC2
pins. Refer to Figure
17-11 for connection.
2. A constant LCD drive voltage can be supplied regardless of changes in V
DD
.
Remark
For the LCD reference voltage (V
LCD2
), refer to
LCD controller/driver characteristics
in
CHAPTER
24 ELECTRICAL SPECIFICATIONS
.
Figure 17-11. Example of Circuit to Adjust LCD Driver Reference Voltage
Remark
Use a capacitor with as little leakage as possible. Use a non-polarity capacitor as C1.
V
LC0
V
LC1
V
LC2
R1
R2
C2
C3
C4
V
LCDC
CAPH
C1
External pin
CAPL
C1 = C2 = C3 = C4 = 0.47 F