HD66724 Datasheet, PDF (68/117 Pages) Hitachi Semiconductor – (Graphics LCD Controller/Driver with Key Scan Function)

HD66724/HD66725
Power Supply for Liquid Crystal Display Drive
When External Power Supply and Internal Operational Amplifiers are Used
To supply LCD drive voltage directly from the external power supply without using the internal booster,
circuits should be connected as shown in figure 36. Here, contrast can be adjusted through the CT bits of
the contrast control instruction.
The HD66724/HD66725 incorporate a voltage-follower operational amplifier for each V1 to V5 to reduce
current flowing through the internal bleeder-resistors, which generate different levels of liquid-crystal drive
voltages. Thus, 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.
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