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ST62T45B/E45B
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 18.
Table 18. Multiplexing ratio
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 19).
Table 19. LCD Frame Frequency Selection
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 ex-
ternal connection of the 1/3VLCD and 2/3VLCD
pins (Figure 27).
Figure 27. Bias Config for 1/2 Duty
Figure 28. Typical Current consumption on
VLCD
Pin
(25
°C, no load, fLCD=512Hz,
mux=1/3-1/4)
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.
DS1
DS0
Display Mode
Active backplanes
0
1/4 mux.ratio
COM1, 2, 3, 4
0
1
1/1 mux.ratio
COM1
1
0
1/2 mux.ratio
COM1, 2
1
1/3 mux.ratio
COM1, 2, 3
LF2
LF1
LF0
Base
fLCD
(Hz)
Frame Frequency fF (Hz)
1/1
mux.
ratio
1/2
mux.
ratio
1/3
mux.
ratio
1/4
mux.
ratio
0
64
32
21
16
0
1
85
43
28
21
0
1
0
128
64
43
32
0
1
171
85
57
43
1
0
256
128
85
64
1
0
1
341
171
114
85
1
0
512
256
171
128
1
Reserved
VLCD
VLCD1/3
VSS
VLCD2/3
RH
LCDOFF
VR01367
ILCD(A)
VLCD(V)
70
60
50
40
30
20
10
34
56
7
8
9
10
VR01838
48