ST6285B View Datasheet(PDF) - STMicroelectronics

Part Name

Description

MFG CO.

ST6285B

8-BIT OTP/EPROM MCU WITH LCD DRIVER, EEPROM AND A/D CONVERTER

STMicroelectronics 

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ST62T85B/E85B

LCD CONTROLLER-DRIVER (Cont”d)

4.7.1 Multiplexing ratio and frame frequency

setting

Up to 16 common plates COM1..COM16 can be

used for multiplexing ratio of 1/8, 1/11 and 1/16.

The selection is made by the bits MUX11 and

MUX16 of the LCDCR as shown in the Table 21.

Table 21. Multiplexing ratio

Figure 30. Bias Config for 1/2 Duty

VS

Contrast

C5

VS

VLCD

MUX11 MUX16 Display Mode Active backplanes

R5

0

0 1/8 mux.ratio

COM1-8

C4

1

0 1/11 mux.ratio COM1-16

C4

VLCD 4/5

Contrast

VLCD

0

1 1/16 mux.ratio COM1-16

1

1-

Reserved

R4

R4

C3

C3

If the 1/1 multiplexing ratio is chosen, LCD seg-

VLCD 3/5

VLCD 4/5

ments are refreshed with a frame frequency Flcd

derived from 32Khz clock with a division ratio de-

) fined by the bits LF0..LF2 of the LCDCR.

t(s When a higher multiplexing ratio is set, refreshment

c frequency is decreased accordingly (Table 22).

du Table 22. LCD Frame Frequency Selection

ro Base

P LF1 LF0 fLCD

Frame Frequency fF (Hz)

1/8

1/11

1/16

te (Hz) mux.ratio mux.ratio mux.ratio

le 0

1 128

128

93

64

o 1

0 170

170

124

85

s 0

0 256

256

186

128

b 1

1 512

512

372

256

O 1

1

Reserved

) - 4.7.2 Segment and common plates driving

t(s LCD panels physical structure requires precise

c timings and stepped voltage values on common

u and segment outputs. Timings are managed by

d the LCD controller, while voltages are generated

ro through an external resistive bridge. In 1/11 and

1/8 multiplexing mode, VLCD 2/5 and VLDCD 3/5

Obsolete P are shorted as seen on Figure 30.

R3

R3

C2

C2

VLCD 3/5

VLCD 2/5

VLCD 2/5

R2

R2

C1

C1

VLCD 1/5

VLCD 1/5

R1

R1

GND

1/5 bias

(1/16 MUX)

GND

1/4 bias

(1/11, 1/8 MUX)

R2 to R5 should be 1KΩ to 200KΩ

C1 to C5 should be 0µF to 0.3 µF VR001662

Note: For display voltages VLCD < 4.5V the resis-

tivity of the divider may be too high for some appli-

cations (especially using 1/3 or 1/4 duty display

mode). In that case an external resistive divider

must be used to achieve the desired resistivity.

56/78

56

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