HD66760 Datasheet, PDF (72/105 Pages) Hitachi Semiconductor – 104 X 80-dot Graphics LCD Controller/Driver for 256 Colors

HD66760
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 step-up
circuit, circuits should be connected as shown in figure 49. Here, contrast can be adjusted by software
through the CT bits of the contrast adjustment register. Minimize the voltage variation since the VLREF
input is a reference voltage that determines the LCD drive voltage.
The HD66760 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_LPS 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 1 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.