HD66760 Datasheet, PDF (79/105 Pages) Hitachi Semiconductor – 104 X 80-dot Graphics LCD Controller/Driver for 256 Colors

HD66760
Example of Power-supply Voltage Generator for More Than Seven-times Step-up Output
The HD66760 incorporates a step-up circuit for up to six-times step-up. However, the LCD drive voltage
(VLCD) will not be enough for six-times step-up 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 step-up can be set higher than the power-supply voltage of Vcc.
Set the Vci input voltage for the step-up circuit to 3.6 V or less within the range of Vcc + 1.0 V. Control the
Vci voltage so that the step-up output voltage (VLOUT) should be less than the absolute maximum ratings
(16.5 V).
HD66760
Battery
3.6 V
Regulator
(1)
2.0 V
Regulator
(2)
2.2 V
GND
VLCD (= 15.4 V)
(VLPS-GND)
2.2 V x 7 = 15.4 V
Vcc ^{Logic circuit}
Vci
Step-up circuit
VLOUT
C1+
C1 –
C2+
C2 –
C3+
C3 –
C4+
C4 –
C5+
C5 –
C6+
C6 –
Vci (= 2.2 V)
Vcc (= 2.0 V)
GND (= 0 V)
GND
1 µF
(+)
(B Charac-
teristics)
VLPS
Operational
amplifier
GND
GND
Note: In practice, the LCD drive current lowers
the voltage in the step-up output voltage.
V 1OUT ≥ Vci or Vci
Figure 54 Usage Example of Step-up Circuit at Vci > Vcc
(+)
1 µF
(B Charac-
teristics)
(+)
1 µF
(B Charac-
teristics)
(+)
1 µF
(B Charac-
teristics)
(+)
1 µF
(B Charac-
teristics)
(+)
1 µF
(B Charac-
teristics)
(+)
1 µF
(B Charac-
teristics)
SEG1 to SEG312
COM1 to COM80