• State
  • Locked Locked
  • Replies 3 replies
  • Subscribers 16 subscribers
  • Views 268 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.

Original question:

TMUX1511: SDI Mux 2:1

TMUX1511: SDI Mux 2:1 (Update)

Morteza Zafari
Prodigy 60 points
Part Number: TMUX1511
Other Parts Discussed in Thread: DS25CP104A

Tool/software:

Hi,

As I explained here, I want to make a 2:1 mux for switching 2 SDI video lines (Only HD-SDI is used so the bandwidth is around 1Gb).

The first try was unsuccessful. 

I followed the comments by Kameron Hill and added some 75 resistors to tie the unused pins to GND.

Here is the new schematics design:

I got the board and assembled the parts.

This time the switch works much better. But still, there are some problems.

It works well if the SDI input cable is short (Less than 30cm). 

If it is longer, there is no output video. (There is so much noise or crosstalk that the receiver cannot display the video)

I have also attached the full PCB + schematics for anyone else interested.

SDI-Mux-v1.0.3.rar

  • 0
    TI__Genius 15280 points

    Hello again Morteza,

    So looking at your schematic, I think the TMUX1511 is not causing the errors you are seeing with long SDI cables.

    Here is a good video that talks about SDI system design.

    I am not a expert in SDI but from what I have gathered and looking at your schematic you might need something called a adaptive cable equalizer.

    Let me loop another TI team who can help in with this

    Regards,

    Kameron

  • 0 in reply to Kameron Hill
    Prodigy 60 points

    Hi Kameron and thanks for the feedback

    I need to test the board with a Tektronix WFM and report back.

    Regarding the cable equalizer you mentioned, I think it poses some problems (Correct me if I am wrong please):

    1. Cable equalizers' output is differential but SDI is single-ended. So there would be two options:
      1. Use one of the outputs of the cable equalizer and terminate the other,
      2. Change the mux to a differential mux.
    2. SDI is 75ohm but cable equalizers' outputs are 50ohm (Then I need to add a cable-driver too)
    3. The main goal of this project was to make a simple switch (Low BOM count and space).
      I have already designed and successfully tested an SDI crosspoint switch using DS25CP104A. It was bulky but worked well.

    Thanks a lot for the support.

    Morteza

  • 0 in reply to Morteza Zafari
    TI__Genius 15280 points

    Hello Morteza,

    Thanks for the response and let me try to explain what I know based of my understanding.

    1.From what I have read you can use equalizers in  single ended configuration by terminating the unused input and output.

    2.I am not sure about this part as I have found a e2e saying that there are equalizers with 75ohm output impedance. I do understand the confusion but we can wait for the SDI team to take a look and explain how to use and which equalizer to use if that is the path you want to go down.

    3. I believe this device has more integrated features than the TMUX1511 and has the equalizer functionality that helps it perform well in this application.

    If using more components with the TMUX1511 is not suitable than using the SDI Crosspoint switch might be our best option.

    Please let me know if this helps and we can wait and see if the HSSC team has any opinions here!

    Regards,

    Kameron