M38258MCM Datasheet, PDF (32/70 Pages) Mitsubishi Electric Semiconductor – SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

MITSUBISHI MICROCOMPUTERS
3825 Group
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
Voltage Multiplier (3 Times)
The voltage multiplier performs threefold boosting. This circuit in-
puts a reference voltage for boosting from LCD power input pin
VL1. (However, when using a 1/2 bias, connect VL1 and VL2 and
apply voltage by external resistor division.)
The voltage multiplier control bit (bit 4 of the LCD mode register)
controls the voltage multiplier.
When voltage is input to the VL1 pin during operating the voltage
multiplier, voltage that is twice as large as VL1 occurs at the VL2
pin, and voltage that is three times as large as VL1 occurs at the
VL3 pin.
When using the voltage multiplier; after applying 1.3 V ≤ Voltage ≤ 2.3 V
to the VL1 pin, set the voltage multiplier control bit to “1” to select the
voltage multiplier enable.
When not using the voltage multiplier, apply proper voltage to the
LCD power input pins (VL1–VL3).
Bias Control and Applied Voltage to LCD
Power Input Pins
To the LCD power input pins (VL1–VL3), apply the voltage shown
in Table 9 according to the bias value.
Select a bias value by the bias control bit (bit 2 of the LCD mode
register).
Common Pin and Duty Ratio Control
The common pins (COM0–COM3) to be used are determined by
duty ratio.
Select duty ratio by the duty ratio selection bits (bits 0 and 1 of the
LCD mode register).
Table 9. Bias control and applied voltage to VL1–VL3
Bias value
Voltage value
1/3 bias
1/2 bias
VL3=VLCD
VL2=2/3 VLCD
VL1=1/3 VLCD
VL3=VLCD
VL2=VL1=1/2 VLCD
Note : VLCD is the maximum value of supplied voltage for the
LCD panel.
Table 10. Duty ratio control and common pins used
Duty
ratio
2
3
4
Duty ratio selection bit
Bit 1
Bit 0
0
1
1
0
1
1
Common pins used
COM0, COM1 (Note 1)
COM0–COM2 (Note 2)
COM0–COM3
Notes 1: COM2 and COM3 are open
2: COM3 is open
VL3
VL2
C2
C1
VL1
1/3 bias
when using the voltage multiplier
Fig. 30 Example of circuit at each bias
Contrast control
Contrast control
VL3
R1
VL2
C2
Open
R2
C1
Open
VL1
R3
R1=R2=R3
1/3 bias
when not using the voltage multiplier
VL3
R4
VL2
C2
Open
C1
Open
VL1
R5
1/2 bias
R4=R5
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