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3.2.3 Video circuit
Video circuit is mainly responsible for the input of external video signals, the processing of video
signals send from tuner, and the drive processing of LCD screen, including video input selection, video
A/D conversion circuit, LCD picture processing circuit and video output circuit. Video circuit block diagram
is shown in the figure 3.2.3.1:
1. Video input and video processing circuit
His circuit is mainly composed of FSAV433 and MST718, MST718 supports NTSC, PAL and
SECAM video signals and the supportable video signal format has RGB, YPbPr, CVBS or S-video video.
The built-in A/D converter can realize multi- format’s conversion function. MST718 adds video switch,
A/D converter and MCU on the basis of MST518 and MST718 also has video output function. Output jack
includes TTL, LVDS modes.
When machine is set in DVD or DVB mode, Y PB Pr signal is inputted to pin 2/6/10 of FSAV433,
and then output from pin 13/15/17 after being selected through electronic switch (FSAV433) to MST718
for A/D conversion. At the same time, Mt1389 also outputs composite video signal, after being selected
through the internal video electronic switch of MST718, output from pin 34 of MST718 to the video
amplifying circuit composed of Q100, Q1 and then output to SCART video output pin.
U101
MST718
LCD picture
processor&
MCU
PANEL
U106
Video
Electronic
switch
FSAV433
SCART
JACK
Y PB PR
INPUT
JACK
video
amplifying
TUNER
/DCVBS-
22/23
34
67
66
SDARX
SCLTX
SCVBS+
SCVBS-
25
24
TV+/TV-
30/31
PRIN
PBIN
Y
7/8
9/10
12/13
SR SGSB
EY
EPB
EPR
DY
DPB
DPR
DG0~DG7
DB0~DB7
DR0~DR7
HSYNC
VSYNC
DE
CLKO
12MHZ
X101
Mt1389
Figure
3.2.3.1
Video circuit block diagram
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