HD66750 Datasheet, PDF (52/96 Pages) Hitachi Semiconductor – 128 x 128-dot Graphics LCD Controller/Driver with Four-grayscale Functions

HD66750/1
Liquid Crystal Display Voltage Generator
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 35. Here, contrast can be adjusted by software through the
CT bits of the contrast adjustment register.
The HD66750/1 incorporates 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 difference between V_LCD and V1 must be 0.1 V or higher, and that between V4 and
GND must be 1.4 V or higher. Note that the OPOFF pin must be grounded when using the operational
amplifiers. Place a capacitor of about 0.47 µF (B characteristics) between each internal operational
amplifier (V1OUT to V5OUT outputs) and GND and stabilize the output level of the operational amplifier.
Adjust the capacitance value of the stabilized capacitor after the LCD panel has been mounted and the
screen quality has been confirmed.
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