HD66740 Datasheet, PDF (51/95 Pages) Hitachi Semiconductor – 112 x 80-dot Graphics LCD Controller/Driver

HD66740
Example of Power-supply Voltage Generator for More Than Five-times Boosting Output
The HD66740 incorporates the booster for up to five-times boosting. However, the LCD drive voltage
(VLCD) will not be enough for five-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.
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 (17 V).
HD66740
Battery
3.6 V
GND
VLCD (= 15 V)
Regula
-tor
(1)
2.5 V
Regula
-tor
(2)
3.0 V
3.0 x 5 = 15 V
Vcc ^{Logic circuit}
C1+
Vci
C1-
C2+
Booster
C2-
C3+
C3-
VLOUT
C4+
C4-
1 µF ⁺
GND
VLCD LCD driver
GND
Vcc (= 3 V)
Vcc (= 2.5 V)
GND (= 0 V)
GND
+
1 µF
+
1 µF
+
1 µF
+
1 µF
SEG1 to SEG112
COM1 to COM80
Figure 26 Usage Example of Booster at Vci > Vcc
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