Texas Instruments THS7303EVM Evaluation Module THS7303EVM THS7303EVM 데이터 시트
제품 코드
THS7303EVM
GND
CH.2 IN B
CH.3 IN B
I 2C-A0
SDA
V
S +
11
12
13
14
15
16
17
18
19
20
SCL
CH.3 SAG
I 2C-A1
CH.1 IN B
CH.2 IN A
CH.3 IN A
CH.1 IN A
NC
CH.3 OUT
CH.2 SAG
CH.2 OUT
CH.1 SAG
CH.1 OUT
NC
1
2
3
4
5
6
7
8
9
10
P’
R
Out 2
+
P’
R
Out 1
+
P’
B
Out 2
+
P’
B
Out 1
+
Y’
Out 2
+
Y’
Out 1
+
DAC /
Encoder
(THS8200)
Y’
P’
B
P’
R
External
Input
Y’
P’
B
P’
R
R
R
R
HDTV
480i
576i
576i
480p
576p
720p
576p
720p
1080i
1080p
3.3 V
75 W
75 W
75 W
75 W
75 W
75 W
75 W
75 W
75 W
75 W
75 W
75 W
75 W
75 W
75 W
0.1 F
m
0.01 F
m
470 F
(See Note A)
m
470 F
(See Note A)
m
470 F
(See Note A)
m
470 F
(See Note A)
(See Note A)
m
470 F
(See Note A)
(See Note A)
m
470 F
(See Note A)
(See Note A)
m
100 F
m
1 F
m
1 F
m
3.3 V
I C
Controller
2
AC STC
AC Bias
AC Bias
DC + 135 mV
DC + 135 mV
DC + 135 mV
SLOS479B
–
OCTOBER 2005
–
REVISED MARCH 2011
OUTPUT MODES OF OPERATION: AC-COUPLED
The most common method of coupling the video signal to the line is by using a large capacitor. This capacitor is
typically between 220
typically between 220
μ
F and 1000
μ
F, although 470
μ
F is most common. This value of this capacitor must be
this large to minimize the line tilt (droop) and/or field tilt associated with ac coupling as described previously in
this document. Just like the dc output configuration, connection of the output pin of each channel directly to the
SAG output pin of the corresponding channel should be as close as possible to the output pins of the THS7303.
this document. Just like the dc output configuration, connection of the output pin of each channel directly to the
SAG output pin of the corresponding channel should be as close as possible to the output pins of the THS7303.
The most common reason ac coupling is used is to ensure full interoperability with the receiving video system.
This ensures that regardless of the reference dc voltage used on the transmit side of the video signal, the receive
side will re-establish the dc reference voltage to its own requirements without any interaction from the transmit
side dc bias voltage.
This ensures that regardless of the reference dc voltage used on the transmit side of the video signal, the receive
side will re-establish the dc reference voltage to its own requirements without any interaction from the transmit
side dc bias voltage.
As with the dc output mode of operation, each line should have a 75-
Ω
source termination resistor in series with
the ac-coupling capacitor. If two 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
resistor rather than sharing these components, as shown in
.This helps ensure line-to-line dc isolation
and other potential problems. Using a single 1000-
μ
F capacitor for two lines can be done, but there is a chance
for interference between the two receivers.
A.
Due to the high frequency content of the video signal, it is recommended, but not required, to add a 0.01-
μ
F capacitor
in parallel with these large capacitors.
Figure 65. Typical Y
'
P
'
B
P
'
R
System Driving 2 AC-Coupled Video Lines
Because of the edge rates and frequencies of operation, it is recommended (but not required) to place a 0.1-
μ
F
to 0.01-
μ
F capacitor in parallel with the large 220-
μ
F to 1000-
μ
F capacitors. These large value capacitors are
most commonly aluminum electrolytic. It is well known that these capacitors have significantly large equivalent
series resistance (ESR), and their impedance at high frequencies is large as a result of the associated
inductances involved with their construction. The small 0.1-
series resistance (ESR), and their impedance at high frequencies is large as a result of the associated
inductances involved with their construction. The small 0.1-
μ
F to 0.01-
μ
F capacitors help pass these
high-frequency (
>
1 MHz) signals with lower impedance than the large capacitors. This is especially true when
HD and computer R'G'B' signals are being used. Their associated edge rates and frequency content can reach
beyond 30-MHz for HD signals and can be over 100-MHz for R'G'B' signals
beyond 30-MHz for HD signals and can be over 100-MHz for R'G'B' signals
—
frequencies that typical aluminum
electrolytic capacitors typically cannot pass effectively.
30
Copyright
©
2005
–
2011, Texas Instruments Incorporated
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