H8-3857 Datasheet, PDF (389/560 Pages) Renesas Technology Corp – 8-Bit Single-Chip Microcomputer

13. Dot Matrix LCD Controller (H8/3857 Group)
13.3.13 LCD Voltage Generation Circuit
When Using External Power Supply and Built-In Op-Amps
When the built-in step-up circuit is not used, and the LCD drive voltages are supplied directly
from an external power supply, connections should be made as shown in figure 13.15. The V_LCD
input level must be between V_CC and 7.0 V.
The LCD controller includes bleeder resistances that generate levels V1 to V5, and voltage
follower op-amp circuits. Set the OPON bit in control register 2 (LR1) to 1. Contrast can be
controlled by software, using the contrast control register (LRA).
If the capacitance of the LCD panel to be driven is large, capacitors of around 0.1 to 0.5 μ F
should be inserted between the V1OUT to V5OUT built-in op-amp outputs and V_SS to provide
stabilization. In order for the op-amps to operate normally, the contrast control register (LRA)
should be set so that the potential difference between V_LCD and V1, and between V5 and V_SS, is at
least 0.4 V.
Rev.3.00 Jul. 19, 2007 page 365 of 532
REJ09B0397-0300