THS7318 Datasheet, PDF (6/10 Pages) Texas Instruments – 3-Channel Low-Power EDTV/SDTV Video Line Driver With Low-Pass Filters

THS7318
SLOS517A – JANUARY 2007 – REVISED FEBRUARY 2007
www.ti.com
THS7318 DESCRIPTION
The THS7318 is an integrated analog video processor designed with integrated Butterworth filters and video line
driver amplifiers to provide the analog signal conditioning required for EDTV signals in portable video
applications.
The device accepts 3 inputs; Y’ (Luma), P’_B / CVBS (analog color difference with blue emphasis / composite
video) and P’_R / C’ (analog color difference with red emphasis / chroma), and provides 3 filtered and amplified
outputs; Y’, P’_B / CVBS and P’_R / C’.
The following are detailed descriptions of each channel.
CHANNEL DESCRIPTIONS
All channels are comprised of DC offset, 3rd order Butterworth low pass filter, and output buffer amplifier. All
channels are same except the Y’ and P’_R / C’ output amplifiers are designed to drive one doubly terminated 75Ω
video line and the P’_B / CVBS output amplifier is designed to drive two doubly terminated 75Ω video lines. Even
under the fault condition where one of the video lines is shorted, the P’_B / CVBS output amplifier is capable of
full video performance on the properly terminated output.
DC Offset
The DC offset circuit is used to insure the output is not driven into saturation and video signal is not
compressed. The nominal output offset caused by this circuit is 150 mV.
3^rd Order Butterworth Low Pass Filter
To reduce DAC images that cause aberrations in the video display, a 3^rd order Butterworth low pass filter is
inserted in the signal path. This DAC reconstruction filter is designed for video systems with 54 MSPS DAC
sampling rates like NTSC/PAL 480p/576p EDTV and 480i/576i SDTV video, with nominal 0.1-dB flatness to
11 MHz, -3-dB bandwidth of 20 MHz, and 20 dB attenuation at 43 MHz.
Output Buffer Amplifier
The output buffer amplifiers are designed for a gain of 6 dB. The Y’ and P’_R / C’ output amplifiers are
designed to drive one doubly terminated 75Ω video line and the P’_B / CVBS output amplifier is designed to
drive two doubly terminated 75Ω video lines. Even under the fault condition where one of the video lines is
shorted, the P’_B / CVBS output amplifier is capable of full video performance on the properly terminated
output.
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