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| 型號： | THS7319IZSVR |
| 廠商： | TEXAS INSTRUMENTS INC |
| 元件分類： | 音頻／視頻放大 |
| 英文描述： | 3 CHANNEL, VIDEO AMPLIFIER, PBGA9 |
| 封裝： | 1.50 X 1.50 MM, 0.35 MM HEIGHT, GREEN, UCSP-9 |
| 文件頁數(shù)： | 11/33頁 |
| 文件大小： | 733K |
| 代理商： | THS7319IZSVR |
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DC-COUPLED OUTPUT
AC-COUPLED OUTPUT
www.ti.com.............................................................................................................................................................. SBOS468A – JUNE 2009 – REVISED JULY 2009
this configuration meets industry standards. EIA-770
stipulates that the back-porch shall be 0 V ± 1 V as
The THS7319 incorporates a rail-to-rail output stage
measured at the receiver. With a double-terminated
that can drive the line directly without the need for
load system, this requirement implies a 0-V ± 2-V
large ac-coupling capacitors. This design offers the
level at the video amplifier output. The THS7319 can
best line tilt and field tilt (droop) performance because
easily meet this requirement without issue. However,
no ac-coupling occurs. Keep in mind that if the input
in Japan, the EIAJ CP-1203 specification stipulates a
is ac-coupled, then the resulting tilt as a result of the
0-V ± 0.1-V level with no signal. This requirement can
input ac-coupling continues to be seen on the output,
be met with the THS7319 in disable mode, but while
regardless of the output coupling. The 70-mA output
active it cannot meet this specification without output
current drive capability of the THS7319 is designed to
ac-coupling.
drive the video line while keeping the output dynamic
range as wide as possible.
One concern of dc-coupling, however, arises if the
A very common method of coupling the video signal
line is terminated to ground. If an ac-bias input
to the line is with a large capacitor. This capacitor is
configuration is used or if a dc reference from the
typically between 220
F and 1000 F, although
DAC is applied, such as S-Video C'/component P'B/or
470
F is very typical. The value of this capacitor
component P'R signals, the output of the THS7319
must be large enough to minimize the line tilt (droop)
will have a dc bias on the output, such as 1 V. This
and/or
field
tilt
associated
with
ac-coupling
as
configuration allows a dc current path to flow, such as
described previously in this document. AC-coupling is
1 V/150
= 6.67 mA. The result of this configuration
performed for several reasons, but the most common
is a slightly decreased high output voltage swing and
is to ensure full interoperability with the receiving
an increase in power dissipation of the THS7319.
video system. This approach ensures that regardless
While the THS7319 was designed to operate with a
of the reference dc voltage used on the transmitting
junction temperature of up to +125°C, care must be
side,
the
receiving
side
re-establishes
the
dc
taken to ensure that the junction temperature does
reference voltage to its own requirements.
not exceed this level or else long-term reliability could
suffer. Using a 5-V supply, this configuration can
In the same way as the dc output mode of operation
result
in
an
additional
power
dissipation
of
discussed previously, each line should have a 75-
(5 V – 1 V) × 6.67 mA = 26.7 mW per channel. With a
source
termination
resistor
in
series
with
the
3.3-V supply, this dissipation reduces to 15.3 mW per
ac-coupling capacitor. This 75-
series resistor
channel. The overall low quiescent current of the
should be placed next to the THS7319 output to
THS7319 design minimizes potential thermal issues
minimize capacitive loading effects.
even when used at high ambient temperatures, but
Because of the edge rates and frequencies of
power and thermal analysis should
always
be
operation, it is recommended (but not required) to
examined in any system to ensure that no issues
place a 0.1-
F to 0.01-F capacitor in parallel with
arise.
Be
sure
to
use
RMS
power
and
not
the large 220-
F to 1000-F capacitor. These large
instantaneous power when evaluating the thermal
value capacitors are most commonly aluminum
performance.
electrolytic. It is well-known that these capacitors
Note that the THS7319 can drive the line with
have significantly large equivalent series resistance
dc-coupling
regardless
of
the
input
mode
of
(ESR), and the impedance at high frequencies is
operation. The only requirement is to make sure the
rather large as a result of the associated inductances
video line has proper termination in series with the
involved with the leads and construction. The small
output (typically 75
). This requirement helps isolate
0.1-
F to 0.01-F capacitors help pass these
capacitive loading effects from the THS7319 output.
high-frequency signals (greater than 1 MHz) with
Failure to properly isolate capacitive loads may result
much lower impedance than the large capacitors.
in ringing or oscillation. The stray capacitance
Although it is common to use the same capacitor
appearing directly at the THS7319 output pins should
values for all the video lines, the frequency bandwidth
be kept below 18-pF. One method to ensure this
of the chroma signal in a S-Video system is not
condition is to make sure the 75-
source resistor is
required to go as low (or as high of a frequency) as
placed next to each THS7319 output pin.
the luma channels. Thus, the capacitor values of the
There are many reasons dc-coupling is desirable,
chroma line(s) can be smaller, such as 0.1
F.
including reduced costs, printed circuit board (PCB)
area, and no line tilt or field tilt. A common question is
whether or not there are any drawbacks to using
dc-coupling. There are a few potential issues that
must be examined, such as the dc current bias as
discussed above. Another potential risk is whether
Copyright 2009, Texas Instruments Incorporated
19
Product Folder Link(s): THS7319
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| THS7319IZSVT | 功能描述:視頻放大器 3Ch Very Lo Pwr Lo Prof EDTV Video Amp RoHS:否 制造商:ON Semiconductor 通道數(shù)量:4 電源類型: 工作電源電壓:3.3 V, 5 V 電源電流: 最小工作溫度: 最大工作溫度: 封裝 / 箱體:TSSOP-14 封裝:Reel |
| THS7320 | 制造商:TI 制造商全稱:Texas Instruments 功能描述:3-Channel ED Filter Video Amplifier with 4-V/V Gain |
| THS7320IYHCR | 制造商:Texas Instruments 功能描述:3-CHANL ED FILTER VIDEO AMP, 4V/V GAIN - Tape and Reel 制造商:Texas Instruments 功能描述:IC 3-CH INTEG VIDEO AMP 9DSBGA 制造商:Texas Instruments 功能描述:Video Amplifiers 3-Ch ED Fltr Video Amp w/ 4V/V Gain 制造商:Texas Instruments 功能描述:3-Chanl ED Filter Video Amp, 4V/V Gain |
| THS7320IYHCT | 制造商:Texas Instruments 功能描述:IC 3-CH INTEG VIDEO AMP 9DSBGA |
| THS7320YHCEVM | 制造商:Texas Instruments 功能描述:THS7320YHCEVM - Boxed Product (Development Kits) 制造商:Texas Instruments 功能描述:Texas Instruments THS7320YHCEVM Development Kits 制造商:Texas Instruments 功能描述:MODULE EVAL FOR THS7320 ZSV 制造商:Texas Instruments 功能描述:EVAL BOARD, THS7320 VIDEO AMPLIFIER, Silicon Manufacturer:Texas Instruments, Silicon Core Number:THS7320, Kit Application Type:Amplifier, Application Sub Type:Video Buffer and Filter, Kit Contents:Eval Board THS7320 |
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