ST62E80B STMICROELECTRONICS [STMicroelectronics], ST62E80B Datasheet - Page 58

• Manufacturer Part Number: ST62E80B
• Description: 8-BIT OTP/EPROM MCU WITH LCD DRIVER, EEPROM AND A/D CONVERTER
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

ST62T80B/E80B
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 20.
Table 20. 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 21).
Table 21. LCD Frame Frequency Selection
4.7.2 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 generated
through an external resistive bridge. In 1/11 and
1/8 multiplexing mode, VLCD 2/5 and VLDCD 3/5
are shorted as seen on Figure 32.
58/78
58
MUX11 MUX16
LF1
0
1
0
1
1
0
1
0
1
LF0
1
0
0
1
1
0
0
1
1
Base
f
(Hz)
128
170
256
512
LCD
1/8 mux.ratio
1/11 mux.ratio
1/16 mux.ratio
-
Display Mode
mux.ratio
Frame Frequency f
128
170
256
512
1/8
Reserved
mux.ratio
Active backplanes
COM1-8
COM1-16
COM1-16
Reserved
1/11
124
186
372
93
mux.ratio
F
(Hz)
1/16
128
256
64
85
Figure 32. Bias Config for 1/2 Duty
Note: For display voltages V
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.
C5
C4
C3
C2
C1
R5
R4
R3
R2
R1
(1/16 MUX)
1/5 bias
R2 to R5 should be 1K
C1 to C5 should be 0 F to 0.3 F
VS
Contrast
VLCD
GND
VLCD 4/5
VLCD 3/5
VLCD 2/5
VLCD 1/5
LCD
to 200K
C4
C3
C2
R4
R3
R2
C1
R1
(1/11, 1/8 MUX)
< 4.5V the resis-
1/4 bias
VS
Contrast
VLCD
VLCD 4/5
VLCD 3/5
VLCD 2/5
VLCD 1/5
GND
VR001662