Datasheet

RL78/L12 CHAPTER 14 LCD CONTROLLER/DRIVER
R01UH0330EJ0200 Rev.2.00 635
Dec 13, 2013
14.8.3 Capacitor split method
RL78/L12 contains an internal voltage reduction circuit for generating LCD drive power supplies. The internal voltage
reduction circuit and external capacitors (0.47
μ F±30%) are used to generate an LCD drive voltage. Only 1/3 bias mode
can be set for the capacitor split method.
Different from the external resistance division method, there is always no current flowing with the capacitor split method,
so current consumption can be reduced.
Table 14-12. LCD Drive Voltages (Capacitor Split Method)
Bias Method
LCD Drive Voltage Pin
1/3 Bias Method
VL4 VDD
VL3
−
VL2 2/3 × VL4
VL1 1/3 × VL4
Figure 14-24. Examples of LCD Drive Power Connections (Capacitor Split Method)
Note When switching to internal voltage boosting, connect the capacitor C4 as shown in figure 14-23 Examples of
LCD Drive Power Connections (Internal Voltage Boosting Method).
Remark Use a capacitor with as little leakage as possible.
In addition, make C1 a nonpolar capacitor.
• 1/3 bias method
VL4
Note
VDD
VL3/P125
V
L2
C2 C3
1/3  VL4
2/3  VL4
CAPH
CAPL
C1
VL1
Drive voltage
generator
VDD