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Preliminary Specifications REV.E
Specifications in this manual are tentative and subject to change.
LCD Drive Control Circuit
Mitsubishi microcomputers
M30220 Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
126
Voltage Multiplier
The voltage multiplier performs threefold boosting. This circuit inputs a reference voltage for boosting
from LCD power input pin V
L1
. (However, when using a 1/2 bias, connect V
L1
and V
L2
and apply voltage
by external resistor division.)
To activate the voltage multiplier, choose the segment/port and duty rate, select bias control, and set up
the LCD frame frequency counter and LCDCK count source using the segment enable register and LCD
mode register, then enable the LCD output enable bit (bit 7 at address 0122
16
) and set the voltage
multiplier control bit (bit 4 at address 0120
16
) to “1” (= voltage multiplier enabled).
When voltage is input to the V
L1
pin during operating the voltage multiplier, voltage that is twice as large
as V
L1
occurs at the V
L2
pin, and voltage that is three times as large as V
L1
occurs at the V
L3
pin.
The voltage multiplier control bit (bit 4 of the address 0120
16
) controls the voltage multiplier.
When using the voltage multiplier, apply a voltage equal to or greater than 1.3 V but not exceeding 2.1 V
to the V
L1
pin before enabling the voltage multiplier control bit.
When not using the voltage multiplier, enable the LCD output enable bit and apply an appropriate voltage
to the LCD power supply input pins (V
L1
to V
L3
). When the LCD output enable bit is disabled, the V
L3
pin
is connected to V
CC
internally.
Table 1.16.2. Bias control and applied voltage to V
L1
to V
L3
Bias value
Voltage value
V
L3
= V
LCD
V
L2
= 2/3 V
LCD
V
L1
= 1/3 V
LCD
V
L3
= V
LCD
V
L2
= V
L1
= 1/2 V
LCD
1/3 bias
1/2 bias
Note : V
LCD
is the maximum value of supplied voltage for the LCD panel.
Figure 1.16.3. Example of circuit at each bias
V
L3
V
L2
C
2
C
1
V
L1
1/3 bias
when using the voltage multiplier
V
L3
V
L2
C
2
C
1
V
L1
1/3 bias
when not using the voltage multiplier
Open
Open
R2
R1
R3
R1=R2=R3
Contrast control
V
L3
V
L2
C
2
C
1
V
L1
1/2 bias
Open
Open
R4
R5
R4=R5
Contrast control
When selecting LCDRAM data output
(not using LCD panel)
V
L1
V
L3
V
L2
C
1
C
2
Open
Open
Bias Control and Applied Voltage to LCD Power Input Pins
To the LCD power input pins (V
L1
to V
L3
), apply the voltage shown in Table 1.16.2 according to the bias value.
Select a bias value by the bias control bit (bit 2 of the address 0120
16
).