HD66750 Datasheet, PDF (58/96 Pages) Hitachi Semiconductor – 128 x 128-dot Graphics LCD Controller/Driver with Four-grayscale Functions

HD66750/1
Example of Power-supply Voltage Generator for More Than Seven-times Boosting Output
The HD66750/1 incorporates a booster for up to seven-times boosting. However, the LCD drive voltage
(VLCD) will not be enough for seven-times boosting from Vcc when the power-supply voltage of Vcc is
low or when the LCD drive voltage is high for the high-contrast LCD display. In this case, the reference
voltage (Vci) for boosting can be set higher than the power-supply voltage of Vcc.
When the boosting factor is high, the current driving ability is lowered and insufficient display quality may
result. In this case, the boosting ability can be improved by decreasing the boosting factor as shown in the
booster in figure 39.
Set the Vci input voltage for the booster to 3.6 V or less within the range of Vcc + 1.0 V. Control the Vci
voltage so that the boosting output voltage (VLOUT) should be less than the absolute maximum ratings
(16.5 V).
HD66750/ 1
B attery
3.6 V
Regu-
lator
(1)
1.8 V
Regu-
lator
(2)
2.2 V
GND
VLCD (= 15.4 V)
2.2 V x 7 = 15.4 V
Vci (= 2. 2 V)
Vcc (= 1. 8 V)
GND (= 0 V)
GND
1 µF
( +)
(B Charac-
teri s tics )
VVccic _{L ogic circuit}
Vc i
B ooster
VLOUT
C1+
C1 Ð
C2+
C2 Ð
C3+
C3 Ð
C4+
C4 Ð
C5+
C5 Ð
C6+
C6 Ð
VLCD LCD driver
GND
GND
Note: I n pract ice, t he LCD drive current lowers
t he volt age in t he boost ing out put volt age.
Figure 39 Usage Example of Booster at Vci > Vcc
( +)_{1 µF}
(B Charac-
teri s tics )
( +)_{1 µF}
(B Chara c-
teristic s)
( +)
1 µF
(B Chara c-
teristic s)
( +)
1 µF
(B Ch arac-
teristi cs)
( +)
1 µF
(B Ch arac-
teristi cs)
( +)
1 µF
(B Ch arac-
teristi cs)
SEG1 to SEG128
COM1 t o COM128
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