Because of the Thanksgiving holiday in the U.S., TI E2E™ design support forum responses may be delayed from November 25 through December 2. Thank you for your patience.

  • State TI Thinks Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 1 answer
  • Subscribers 47 subscribers
  • Views 434 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

THS7353?

eli
Guru 13485 points
Other Parts Discussed in Thread: THS7353, THS7303, THS7368, THS7360

would like to use a video buffer THS7353 , to drive the analog video output from the board.

 The intention is to use an input mux. for SD / HD selection as only 3 outputs are available in the interface connector.
 
Is this selection correct? If not – can you recommend a different solution?
  • 0
    TI__Expert 3030 points

    Eli,

    While the THS7353 can work, I would recommend the THS7303 instead. The biggest reason is it sounds like you wish to be driving a video line out of your system. Due to double termination of the video line (75-ohm source resistor and 75-ohm end termination), a 2V/V gain is needed to counteract this external double termination attenuation. The THS7303 is designed for this scenario. Simply connect each channel's SAG pin to the corresponding output pin to keep things simple.

    The THS7353 can work, but you will need to add an extra resistor to GND on each channel to increase the gain from 1V/V to 2V/V. The one potential drawback of this is the gain bandwidth product will decrease bypass bandwidth, but should have no impact with the filter modes until gain starts getting larger. Plus the offsets increase with the gain increase which may come into play depending on how the video signal is biased and/or if low supply voltages are utilized.

    Let me know if there are any questions.

    -Randy

  • 0 in reply to Randy S
    Guru 13485 points

    Hi Randy,

    The device shall interface the NETRA DAC.

    The source impedance is 37.5 ohm.

    So I guess that additional resistors should be added anyway.

    Eli

  • 0 in reply to eli
    TI__Expert 3030 points

    Eli,

    The Netra DAC requires different amplifier gains between the SD Channels and Component video channels. CVBS / S-Video Y / C requires gain of 5.6V/V while the Component video channels require a gain of 4.5V/V. This is why the THS7368 was created - to allow for the specific gains of each set and the selectable filters for the Component channels as I believe the Encoder/DAC does not do upsampling for the SD or ED resolutions.

    If you only wish to have one set of connectors for your system, then this makes things a bit more difficult. Do you wish to support all 6-video outputs (CVBS/S-Video/YPbPr) or only a subset of this?

    -Randy

  • 0 in reply to Randy S
    Guru 13485 points

    Hi Randy,

    See below customer feedback:

    "We have a limited pinout in the interface connector, limited board space limited power and probably some other limitations in our design.

    We can route only one type of video via the connector. To do so, we shall multiplex SD and HD video channels. If one device can handle that task (muxing the video and the amplify the signal as required), it will a best solution for us.

    Additional question – shall we route the video signal differentially from the amp. output, or it can be extended from a single to a differential on a base board?

     

    ( THS7360 device as a netra output video driver in the NETRA EVM)