M38264EBFS datasheet(46/91 Pages) RENESAS

46 / 91 page

Rev.1.00

Sep 06, 2006

page 46 of 88

REJ03B0181-0100

3826 Group (One Time PROM version)

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.

Set each bit of the segment output enable register and the LCD

mode register in the following order for operating the voltage mul-

tiplier.

1. Set the segment output enable bits (bits 0 to 5) of the seg-

ment output enable register to “0” or “1”.

2. Set the duty ratio selection bits (bits 0 and 1), the bias con-

trol bit (bit 2), the LCD circuit divider division ratio selection

bits (bits 5 and 6), and the LCDCK count source selection

bit (bit 7) of the LCD mode register to “0” or “1”.

3. Set the LCD output enable bit (bit 6) of the segment output

enable register to “1” (enabled). Apply the limit voltage or

less to the VL1 pin.

4. Set the voltage multiplier control bit (bit 4) of the LCD mode

to select 1/3 bias for bias control.

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.

■Notes on Voltage Multiplier

When using the voltage multiplier, apply the limit voltage or less to

the VL1 pin, then set the voltage multiplier control bit to “1” (en-

abled).

When not using the voltage multiplier, set the LCD output enable

bit to “1”, then apply proper voltage to the LCD power input pins

(VL1–VL3). When the LCD output enable bit is set to “0” (disabled)

(during reset is included), the VL3 pin is connected to VCC inside

of this microcomputer. When the voltage exceeding VCC is applied

to VL3, apply VL3 voltage after setting the LCD output enable bit to

“1” (enabled).

Fig. 48 Example of circuit at each bias

Table 12 Bias control and applied voltage to VL1–VL3

Bias value

1/3 bias

1/2 bias

Voltage value

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.

Bias Control and Applied Voltage to LCD

Power Input Pins

To the LCD power input pins (VL1–VL3), apply the voltage shown

in Table 12 according to the bias value.

Select a bias value by the bias control bit (bit 2 of the LCD mode

R4 = R5

1/2 bias

VCC

VL3

VL2

VL1

R1 = R2 = R3

VCC

VL3

VL2

VL1

VL3

VL2

VL1

Open

Contrast control

Open

Contrast control

1/3 bias

when not using the voltage

multiplier

1/3 bias

when using the voltage

multiplier

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