THS7314 Datasheet, PDF (18/23 Pages) Texas Instruments – 3-Channel SDTV Video Amplifier With 5th-Order Filters and 6-dB Gain

THS7314
SLOS513 – DECEMBER 2006
www.ti.com
APPLICATION INFORMATION (continued)
Just like the DC output mode of operation, each line should have a 75-Ω source termination resistor in series
with the ac-coupling capacitor. If 2 lines are to be driven, it is best to have each line use its own capacitor and
resistor rather than sharing these components as shown in Figure 34. This helps ensure line-to-line dc isolation
and the potential problems as stipulated above. Using a single 1000-µF capacitor for 2-lines can be done, but
there is a chance for ground loops and interference to be created between the two receivers.
Lastly, due to the edge rates and frequencies of operation, it is recommended – but not required – to place a
0.1-µF to 0.01-µF capacitor in parallel with the large 220-µF to 1000-µF capacitor. These large value capacitors
are most commonly aluminum electrolytic. These capacitors have significantly large ESR (equivalent series
resistance), and their impedance at high frequencies is large due to the associated inductances involved with
the leads and construction. The small 0.1-µF to 0.01-µF capacitors help pass these high frequency (>1 MHz)
signals with much lower impedance than the large capacitors.
Although it is common to use the same capacitor values for all the video lines, the frequency bandwidth of the
chroma signal in a S-Video system are not required to go as low – or as high of a frequency – as the luma
channels. Thus the capacitor values of the chroma line(s) can be smaller – such as 0.1-µF.
Y’
330 mf
Out 1
(Note A) _{75 W}
+
3.3 V
Y’
DAC/
Encoder
SDTV
P’_B
480i/576i
Y’P’_BP’_R
G’B’R’
P’_R
3.3 V
R
0.1 mF
3.3 V
3.3 V
3.01 MW
R
0.1 mF
3.3 V
3.3 V
3.01 MW
R
0.1 mF
THS 7314
1 CH.1 IN
2 CH.2 IN
3 CH.3 IN
4 ^VS+
CH.1 OUT 8
CH.2 OUT 7
CH.3 OUT ₆
GND ₅
0.1 mF
3.3 V
+
22 mF
330 mf
(Note A)
75 W
Y’
Out 2
+
330 mf
(Note A)
+
75 W
P’B
Out 1
330 mf
(Note A)
+
P’B
Out 2
75 W
330 mf
(Note A)
+
75 W
P’_R
Out 1
330 mf
P’R
Out 2
(Note A) _{75 W}
+
75 W
75 W
75 W
75 W
75 W
75 W
A. Due to the high frequency content of the video signal, it is recommended, but not required, to add a 0.1-µF or
0.01-µF capacitor in parallel with these large capators.
B. Current sinking DAC / Encoder shown. See the application notes.
Figure 34. Typical 480i/576i Y'P'_BP'_R AC-Input System Driving 2 AC-Coupled Video Lines
18
Submit Documentation Feedback