ST6246 查看數據表（PDF） - STMicroelectronics
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ST6246 Datasheet PDF : 72 Pages
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ST62T46B/E46B
LCD CONTROLLER-DRIVER (Continued)
4.5.1 Multiplexing ratio and frame frequency
setting
Up to 4 common plates COM1..COM4 can be
used for multiplexing ratio ranging from 1/1 to 1/4.
The selection is made by the bits DS0 and DS1 of
the LCDCR as shown in theTable 16.
Table 16. Multiplexing ratio
DS1 DS0 Display Mode
0 0 1/4 mux.ratio
0 1 1/1 mux.ratio
1 0 1/2 mux.ratio
1 1 1/3 mux.ratio
Active backplanes
COM1, 2, 3, 4
COM1
COM1, 2
COM1, 2, 3
If the 1/1 multiplexing ratio is chosen, LCD seg-
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.
When a higher multiplexing ratio is set, refreshment
frequency is decreased accordingly (Table 17).
Table 17. LCD Frame Frequency Selection
Base Frame Frequency fF (Hz)
LF2
LF1
LF0
fLCD
1/1 1/2 1/3
mux. mux. mux.
1/4
mux.
(Hz) ratio ratio ratio ratio
0
0
0 64 64 32 21 16
0
0
1 85 85 43 28 21
0
1
0 128 128 64 43 32
0
1
1 171 171 85 57 43
1
0
0 256 256 128 85 64
1
0
1 341 341 171 114 85
1
1
0 512 512 256 171 128
1
1
1
Reserved
4.5.2 Segment and common plates driving
LCD panels physical structure requires precise
timings and stepped voltage values on common
and segment outputs. Timings are managed by
the LCD controller, while voltages are derivated
from the VLCD value through internal resistive di-
vision. This internal divider is disabled when the
LCD driver is OFF in order to avoid consumption
on VLCD pin.
The 1/3 VLCD and 2/3 VLCD values used in 1/1,
1/3 and 1/4 multiplexing ratio modes are internally
generated and issued on external pins, while 1/2
VLCD value used in 1/2 mode is obtained by exter-
nal connection of the 1/3VLCD and 2/3VLCD pins
(Figure 26).
Figure 26. Bias Config for 1/2 Duty
LCDOFF
VLCD
RH
VLCD2/3
RH
VLCD1/3
RH
VSS
VR01367
Figure 27. Typical Current consumption on
VLCD Pin (25°C, no load, fLCD=512Hz, mux=1/3-
1/4)
ILCD(µA)
70
60
50
40
30
20
10
3 4 5 6 7 8 9 10 VLCD(V)
VR01838
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.
49/72
385
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