hd66421 Renesas Electronics Corporation., hd66421 Datasheet - Page 34

• Manufacturer Part Number: hd66421
• Description: Ram-provided 160 Channel 4-level Grey Scale Driver For Dot Matrix Graphics Lcd
• Manufacturer: Renesas Electronics Corporation.

LCD drive levels bias ratio: LCD driving levels
bias ratio can be selected from 1/8, 1/9, 1/10 or
1/11.
Power Supply: The HD66421 needs the external
power supply for LCD driving circuit. If this
power circuit has on/off control, the HD66421
controls the external power supply circuit by
setting PWR bit.
Resister for
bias current
of operational
amplifier
Preliminary
R4
Vcc
IREFP
GND
IREFM
resistive divider for
partial display mode
VLCD
IV1
IV2
IV3
IV4
IV5
r
r
r
r
HD66421
Figure 31 Power Supply Circuit
Operational
amplifier OFF
Contrast
control
circuit
-
+
-
+
-
+
-
+
-
+
34
External Power Supply Circuit: When the
internal operational amplifier cannot fully drive
the LCD panel used, V1O to V5O voltages can be
supplied from external power supply circuit.
Here, the AMP bit must be set to 1 to turn off the
internal power supply circuit.
R1
R1
R3
R1
R1
R2
Bias
control
VLCD
GREF
DCON
V1O
V2O
V3O
V4O
V5O
R1 = R
R2 = 0.094R to 3R
R3 = 4R to 7R
R4 = 1M to 5M
C1 = 1µF to 3µF
C1
C1
C1
C1
C1
External voltage
booster
Rev. 1.1E '99.02.10
Vout
on/off
HD66421