hd66717 Renesas Electronics Corporation., hd66717 Datasheet - Page 56

• Manufacturer Part Number: hd66717
• Description: Low-power Dot-matrix Liquid Crystal Display Controller/driver -
• Manufacturer: Renesas Electronics Corporation.

HD66717
When an Internal Booster and External Bleeder-Resistors are Used
When the internal operational amplifiers cannot fully drive the LCD panel used, V1 to V5 voltages can
be supplied through external bleeder-resistors (Figure 34). Here, the OPOFF pin must be set to the V
level to turn off the internal operational amplifiers. Since the internal contrast adjuster is disabled in this
case, contrast must be adjusted externally. Double- and triple-boosters can be used as they are.
508
Figure 34 External Bleeder-Resistor Example for LCD Drive Voltage Generation Power Supply
Note: 1. Resistance of each external bleeder resistor should be 5 k to 15 k .
2. The bias current value for driving liquid-crystals can be varied by adjusting
3. The internal contrast-adjuster is disabled; contrast must be adjusted either
4. Vci is both a reference voltage and power supply for the booster; connect it to V
5. Vci must be smaller than V
the resistance (2R) between the V2OUT and V3OUT pins.
by controlling the external variable resistor between V
or combine it with a transistor so that sufficient current can be obtained.
V
CC
GND
VR
+
GND
R
R
2R
R
R
0.47 F
to 1 F
0.47 F
to 1 F
+
0.47 F
to 1 F
V5OUT2
V5OUT3
V1OUT
V2OUT
V3OUT
V4OUT
V5OUT
CC
+
V
V
.
Vci
C1
C2
CC
EE
Circuit
HD66717
OPOFF =
Booster
+
–
+
–
+
–
+
–
+
–
V
V
V1
V2
V3
V4
V5
CC
CC
EE
and V5OUT or Vci for the booster.
CC
directly
CC