E202075_HD404889 Datasheet, PDF (148/202 Pages) Renesas Technology Corp – Low-Voltage AS Microcomputers with On-Chip LCD Circuit

HD404889/HD404899/HD404878/HD404868 Series
1
VCC
COM1
3-digit LCD
VCC
V1
V2
SEG1
V3
to
GND
SEG24
24
Static drive (power supply voltage used for VLCD)
2
VCC
COM1
6-digit LCD
V1
COM2
VCC
V2
SEG1
V3
to
GND
SEG24
24
1/2 duty, 1/2 bias drive (power supply voltage used for VLCD)
VCC
VLCD
VCC
V1
V2
V3
GND
COM1
to
COM3
SEG1
to
SEG24
3
24
8-digit LCD
1/3 duty, 1/3 bias drive (external power supply used for VLCD)
VCC
VLCD
VCC
V1
V2
V3
GND
COM1
to
COM4
SEG1
to
SEG24
4
24
12-digit LCD
1/4 duty, 1/3 bias drive (external power supply used for VLCD)
Figure 91-2 Examples of LCD Wiring (HD404868 Series)
Large LCD panel drive:
If the capacitance of the driven LCD is large, the value of the divided resistance should be reduced by
dividing the resistance in parallel with the built-in divided resistor (see figures 92-1 and 92-2).
As an LCD has a matrix structure, the path of the charge/discharge current flowing to the load capacitance
is complicated. Moreover, the current varies depending on the illumination state, so that it is not possible
to determine the resistance values simply from the LCD load capacitance. The resistance values must
therefore be determined experimentally in accordance with the power consumption requirement of the
equipment, including the LCD. (Adding capacitors C with a value of 0.1 to 0.3 µF is also effective).
A value of 1 kΩ to 10 kΩ is normally set for R.
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