3822 datasheet(33/59 Pages) RENESAS

33 / 59 page

Rev.1.20

Dec 24, 2003

page 33 of 57

3822 Group (A ver.)

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

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).

Fig. 31 Example of circuit at each bias

Table 10 Duty ratio control and common pins used

Duty

ratio

Common pins used

Notes1: COM2 and COM3 are open.

2: COM3 is open.

Bit 1

Bit 0

COM0, COM1 (Note 1)

Duty ratio selection bit

COM0–COM2 (Note 2)

COM0–COM3

Table 9 Bias control and applied voltage to VL1–VL3

Bias value

1/3 bias

Voltage value

VL3=VLCD

VL2=2/3 VLCD

VL1=1/3 VLCD

Note 1: VLCD is the maximum value of supplied voltage for the

LCD panel.

1/2 bias

VL3=VLCD

VL2=VL1=1/2 VLCD

Contrast control

1/2 bias

1/3 bias

Contrast control

VL3

R4 = R5

R1 = R2 = R3

VL2

VL1

VL3

VL2

VL1

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