HD66727 Datasheet, PDF (62/97 Pages) Hitachi Semiconductor – Low-Power Dot-Matrix Liquid Crystal Display Controller/Driver with Key Scan Function

HD66727
a) Double boosting
OPOFF = GND
V_CC
Short-circuited
for 1-or 2-line
display
V_CC ^HD66727
R
V2 ^R
R
+–+- ^V1
+–+- V2
V3 ^R
R
R
VR
V_EE
+–+- ^V3
+–^{+- V4}
+–^{+- V5}
Vci
C1
0.47 µF
to 1 µF + ^C2
0.47 µF
to 1 µF ₊
GND
V5OUT2
V5OUT3
Booster
b) Triple boosting
OPOF = GND
V_CC
Short-circuited
for 1-or 2-line
display
V_CC ^HD66727
R
V2 ^R
R
+– ^V1
+– V2
V3 ^R
R
R
VR
V_EE
+– ^V3
+– ^V4
+– ^V5
Vci
C1
0.47 µF
to 1 µF ⁺
C2
V5OUT2
+
0.47 µF
to 1 µF
GND
V5OUT3
Booster
+
GND
Notes: 1. The reference voltage input (Vci) must be adjusted so that the output voltage after boosting will not exceed
the absolute maximum rating of the liquid-crystal power supply voltage (15V). Particularly, Vci must be
5V or less for triple boosting.
2. Vci is both a reference voltage and power supply for the booster; connect it to V_CC directly or combine it with
a transistor so that sufficient current can be obtained.
3. Vci must be smaller than V_CC.
4. To operate the voltage-follower correctly, potential differences between V_CC and V1 and between V5 and
V_EE must be 0.4V or greater, particularly for low-duty drive such as 1-line display.
5. Polarized capacitors must be connected correclty.
6. Circuits for temperature compensation should be designed based on the sample circuit shown in figure 35.
7. The HD66727's internal operational amplifiers have a reduced drive current to save current consumption;
when the internal operational amplifiers cannot fully drive the LCD panel used, an appropriate capacitor must
be inserted between each output of V1OUT to V5OUT and V_CC to stabilize the operational amplifier output
(Figure 36).
Figure 34 Internal Power Supply Circuit Example for LCD Drive Voltage Generation
HD66727
V_CC
V_CC
Thermistor
Tr ^Vci
GND
Figure 35 Temperature Compensation Circuit Example
62