HD66724 Datasheet, PDF (69/117 Pages) Hitachi Semiconductor – (Graphics LCD Controller/Driver with Key Scan Function)

OPOFF=GND
V LCD
VLCD
VR
V1OUT
R
V2OUT
R0
GND
V3OUT
R
0.1 µF
to 0.5 µF
V4OUT
R
V5OUT
++ + ++
R
GND
HD66724/5
+
-
V1
+
-
V2
LCD
driver
+
-
V3
+
-
V4
+
-
V5
GND
Vci
C1+
C1-
C2+
C2-
VLOUT
Booster
HD66724/HD66725
SEG1 to SEG72 (96)
COM1 to COM24
COMS1 to COMS2
Figure 36 External Power Supply Circuit for LCD Drive Voltage Generation
When an Internal Booster and Internal Operational Amplifiers are Used
To supply LCD drive voltage using the internal booster, circuits should be connected as shown in figure 37.
Here, contrast can be adjusted through the CT bits of the contrast control instruction. Temperature can be
compensated either through the CT bits or by controlling the reference voltage for the booster (Vci pin)
using a thermistor.
Note that Vci is both a reference voltage and power supply for the booster. The reference voltage must
therefore be adjusted using an emitter-follower or a similar element so that sufficient current can be
supplied. In this case, Vci must be equal to or smaller than the V_CC level.
The HD66724/HD66725 incorporate a voltage-follower operational amplifier for each of V1 to V5 to
reduce current flowing through the internal bleeder-resistors, which generate different liquid-crystal drive
voltages. Thus, the potential differences between V_LCD and V1 and between V5 and GND must be 0.1 V or
higher. Note that the OPOFF pin must be grounded when using the operational amplifiers. Place a capacitor
of about 0.1 µF to 0.5 µF between each internal operational amplifier V1out to V5out output and GND and
stabilize the output level of the operational amplifier.
69