M38C89MB datasheet(32/55 Pages) RENESAS

32 / 55 page

SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

MITSUBISHI MICROCOMPUTERS

38C8 Group

Bias Control

In the LCD power source pins (VL1–VL5), 1/7 bias is automatically

generated in 32 duty ratio and 1/5 bias is done in 16 duty ratio as

well. Be sure to connect the capacitor for smoothness to these pins.

When requiring 1/5 bias in 32 duty ratio, use an external resistor to

generate a necessary level. In this case the drivability selection bit 1

of LCD control register 1 must be “1”.

Fig. 29 Example of circuit at each bias

Table 8 Bias control and applied voltage to VL1–VL5

Bias value

Voltage value

VL5 = VLCD

VL4 = 6/7 VLCD

VL3 = 5/7 VLCD

VL2 = 2/7 VLCD

VL1 = 1/7 VLCD

VL5 = VLCD

VL4 = 4/5 VLCD

VL3 = 3/5 VLCD

VL2 = 2/5 VLCD

VL1 = 1/5 VLCD

Note: VLCD is a value which can be supplied to the LCD panel. Set value

which is less than maximum ratings to VLCD.

1/5 bias

in 16 duty ratio

1/7 bias

in 32 duty ratio

•At 1/5 bias

R1=R2=R3=R4=R5

•At 1/7 bias

R1=R2=R4=R5

R3=3•R1

VL5

VL4

VL3

VL2

VL1

VLIN

VL5

VL4

VL3

VL2

VL1

VLIN

VL5

VL4

VL3

VL2

VL1

VLIN

1/5, 1/7 bias

When using voltage multiplier

circuit

1/5, 1/7 bias

When not using voltage

multiplier circuit (1)

1/5, 1/7 bias

When not using voltage

multiplier circuit (2)

1.3 to

2.33 V

Voltage Multiplier

When the voltage multiplier is operated after a reference voltage for

boosting is applied to LCD power supply VLIN, a voltage that is ap-

proximately three times as large as that of VLIN pin occurs at the VL5

pin. Operate the voltage multiplier after applying a reference voltage

for boosting to VLIN.

The voltage multiplier multiplies a VLIN voltage by charge/discharge

of capacitors between C1 and C2 pins and to C3 pin. Accordingly, if a

large LCD panel is driven or a vias value is changed owing to an

external resistor, a level from VL5 pin might be not a requested level.

To prevent this, we recommend use of an external power source

which can supply stabilized power.

Additionally, when using the voltage multiplier, set a higher resistor

value (the sum of R1 to R5) as possible (100 k

Ω or more recom-

mended).

M38C89MB Datasheet(PDF) 32 Page - Renesas Technology Corp

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