HD66421 Datasheet, PDF (34/46 Pages) Hitachi Semiconductor – (RAM-Provided 160 Channel 4-Level Grey Scale Driver for Dot Matrix Graphics LCD)

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