Datasheet

CHAPTER 15 LCD CONTROLLER/DRIVER
406 User’s Manual U18698EJ1V0UD
15.8 Supplying LCD Drive Voltages VLC0, VLC1, VLC2 and VLC3
With the 78K0/LC3, a LCD drive power supply can be generated using either of two types of methods: internal
resistance division method or external resistance division method.
15.8.1 Internal resistance division method
The 78K0/LC3 incorporates voltage divider resistors for generating LCD drive power supplies. Using internal
voltage divider resistors, a LCD drive power supply that meet each bias method listed in Table 15-9 can be generated,
without using external voltage divider resistors.
Table 15-9. LCD Drive Voltages (with On-Chip Voltage Divider Resistors)
Bias Method No Bias (Static) 1/2 Bias Method 1/3 Bias Method 1/4 Bias Method
LCD Drive Voltage Pin
VLC0 VLCD VLCD VLCD VLCD
VLC1 VLCD VLCD
Note
VLCD VLCD
VLC2 VLCD VLCD VLCD
VLC3 VSS VSS VSS VLCD
Note For the 1/2 bias method, it is necessary to connect the V
LC1 and VLC2 pins externally.
Figure 15-23 shows examples of generating LCD drive voltages internally according to Table 15-9.
Figure 15-23. Examples of LCD Drive Power Connections (Internal Resistance Division Method) (1/2)
(a) 1/3 bias method and static display mode
(MDSET1, MDSET0 = 0, 1)
(example of V
DD = 5 V, VLC0 = 5 V)
(b) 1/3 bias method and static display mode
(MDSET1, MDSET0 = 1, 1)
(example of V
DD = 5 V, VLC0 = 3 V)
R
R
R
P-ch
SCOC
P40/KR0
P40/KR0
R
R
R
P-ch
SCOC
P40/KR0
P40/KR0
2R
5
3
V
LC0
V LC0
V LC1
V LC2
V SS
V DD
V SS
V LC1
V LC2
V LC0 = V DD
V LC0
V LC0
V LC1
V LC2
V SS
V DD
V SS
V LC1
V LC2
V LC0 = V DD
Remark It is recommended to use the external resistance division method when using the static display mode, in
order to reduce power consumed by the voltage divider resistor.
2
3
2
3
1
2
1
3
1
3
3
4
2
4
1
4