HD66730 Datasheet, PDF (115/131 Pages) Hitachi Semiconductor – Dot-Matrix Liquid Crystal Display Controller/Driver Supporting Japanese Kanji, Korean Font Display

HD66730/HD66731
Power Supply for Liquid Crystal Display Drive
The HD66730/1 incorporates a booster for raising the LCD voltage two or three times that of the reference
voltage input below V_CC (Figure 48). A two or three times boosted voltage can be obtained by externally
attaching two or three 1-µF capacitors.
If the LCD panel is large and needs a large amount of drive current, the values of bleeder resistors that
generate the V1 to V5 potential are made smaller. However, the load current in the booster and the voltage
drop increases in this case.
We recommend setting the resistance value of each bleeder larger than 4.7 kΩ and to hold down the DC
load current to 0.4 mA if using a booster circuit. An external power supply should supply LCD voltage if
the DC load current exceeds 0.7 mA (Figure 49). Refer to Electrical Characteristics showing the
relationship between the load current and booster voltage output. Table 27 shows the duty factor and
bleeder resistor value for power supply for liquid crystal display drive.
Table 28 Duty Factor and Bleeder Resistor Value for Power Supply for Liquid Crystal Display
Drive
Item
Data
Drive lines (DT1/0 setting value)
1
2
3
4
Duty factor
1/14
1/27
1/40
1/53
Bias
1/4.7
1/6.2
1/7.3
1/8.3
Bleeder resistance value
R1
R
R
R
R
R0
R*0.7
R*2.2
R*3.3
R*4.3
Note: * R changes depending on the size of a liquid crystal panel. Normally, R must be 4.7 kΩ to 20 kΩ.
Adjust R to the optimum value with the consumption current and display picture quality.
V_CC
V_CC
R1
V1
R1
V2
R0
V3
R1
V4
R1
V5
VR
V_EE
Figure 46 Example of Power Supply for Liquid Crystal Display Drive
(with External Power Supply)
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