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13. Dot Matrix LCD Controller (H8/3857 Group)
When Using Built-In Step-Up Circuit and Op-Amps
When the built-in step-up circuit is used, connections should be made as shown in figure 13.17 (1)
(3X step-up) or figure 13.17 (2) (2X step-up).
The LCD controller includes bleeder resistances that generate levels V1 to V5, and voltage
follower op-amp circuits. When the built-in op-amps are used, the OPON bit in control register 2
(LR1) should be set 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 μF should
be inserted between the V1OUT to V5OUT built-in op-amp outputs and V
to provide
SS
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
and V1, and between V5 and V
, is at
LCD
SS
least 0.4 V.
Since the V
pin is also used for the step-up circuit power supply, ensure that an adequate current
ci
can be supplied when carrying out reference voltage adjustment. The V
input level must not
ci
exceed V
.
CC
Rev.3.00 Jul. 19, 2007 page 368 of 532
REJ09B0397-0300
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