PD16715A_15 Datasheet, PDF (11/18 Pages) Renesas Technology Corp – 384-OUTPUT TFT-LCD SOURCE DRIVER(COMPATIBLE WITH 64-GRAY SCALES)

µ PD16715A
8. RELATIONSHIP BETWEEN OUTPUT DATA AND D/A CONVERTER
The µPD16715A is a dot inversion and inverts dots by alternately using a charging output buffer and a discharging
output buffer. Therefore, the output voltage of the first line may not be correctly written because the last line’s output
polarity of frame n (n + 1) and the first line’s output polarity are the same (refer to Figure 8-1).
Consequently, polarity inversion and write operation must be performed between frames (vertical blanking period)
in order to invert (clear) the polarity of the wiring level of the liquid crystal panel by using the last line output of the
previous frame (refer to Figure 8-2).
Figure 8-1. Incase of the output voltage may not be correctly written
STB
POL
S2N
Last line of frame n
,,, _{Discharging output}
buffer
Vertical blanking period
First line of frame
(n + 1)
,,,,,,,,,,,,,,, ^Hi-Z
Hi-Z
Second line of frame
(n + 1)
Charging output
buffer
VCOM
Hi-Z
If the write voltage of the first line of the last (n + 1) frame is greater than the
write voltage of
the last line of frame n, the targeted voltage cannot be correctly written with the
Figure 8-2. Polarity inversion and write operation
STB
POL
S2N
,,, _{Last line of frame n}
Vertical blanking period
First line of frame
(n + 1)
,,,,,,,,,,,,,,,,,, ^Hi-Z
Hi-Z
Hi-Z
Second line of frame
(n + 1)
Hi-Z
VCOM
Because data of negative polarity is to be written on the first line of
frame (n + 1),
Data Sheet S13944EJ2V0DS00
9