HD66750 Datasheet, PDF (51/96 Pages) Hitachi Semiconductor – 128 x 128-dot Graphics LCD Controller/Driver with Four-grayscale Functions

HD66750/1
n-raster-row Reversed AC Drive
The HD66750/1 supports not only the LCD reversed AC drive in a one-frame unit (B-pattern waveform)
but also the n-raster-row reversed AC drive which alternates in an n-raster-row unit from one to 32 raster-
rows (C-pattern waveform). When a problem affecting display quality occurs, such as crosstalk at high-
duty driving of more than 1/64 duty, the n-raster-row reversed AC drive (C-pattern waveform) can improve
the quality. Determine the number of raster-rows n (NW bit set value + 1) for alternating after confirmation
of the display quality with the actual LCD panel. However, if the number of AC raster-rows is reduced, the
LCD alternating frequency becomes high. Because of this, the charge or discharge current is increased in
the LCD cells.
1 frame
1 frame
1 2 3 4 5 6 7 8 9 10 11 12 13
79 80 1 2 3 4 5 6 7 8 9 10 1112 13
79 80 1 2 3
B-pattern
waveform drive
Â¥ 1/80 duty
C-pattern
waveform drive
Â¥ 1/80 duty
Â¥ 11-raster-row
reversal
Â¥ Without EORs
C-pattern
waveform drive
Â¥ 1/80 duty
Â¥ 11-raster-row
reversal
Â¥ With EORs
Note: Specify the number of AC drive raster-rows and the necessity of EOR so that the DC bias is not generated for
the liquid crystal.
Figure 34 Example of an AC Signal under n-raster-row Reversed AC Drive
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