HD66765 Datasheet, PDF (67/71 Pages) Hitachi Semiconductor – 396-channel Segment Driver with Internal RAM for 4096-color Displays

HD66765
n-raster-row Reversed AC Drive
The HD66765 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 64 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
n ^{the LCD cells.}
tio _{1 frame}
1 frame
ifica ^{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 111213 79 80 1 2 3}
c _{B-pat tern}
e _{wa veform drive}
p • 1/80 duty
S _{C-pat tern}
y wav eform drive
r _{• 1/80 duty}
a • 11-raster-row
revers al
in • Without EORs
C- pat tern
lim ^{waveform drive}
• 1/80 duty
e _{• 11-rast er-row}
r _reversal
P • With EORs
Note: Specify the numb er of AC drive raster-rows and the necess ity of EOR so that the DC bias is not generated f
the liquid crys tal.
Figure 50 Example of an AC Signal under n-raster-row Reversed AC Drive
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