• State Resolved
  • Locked Locked
  • Replies 7 replies
  • Subscribers 35 subscribers
  • Views 820 views
  • Users 0 members are here
Support feedback
Options
Options
Related

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.

DS90UB913/914 Over Coax

carlpii
Intellectual 500 points

I am investigating changing the wiring used in our system to 50 ohm micro-coax with a U.FL connector on at least one end.  We have successfully used both shielded twisted pair and 100 ohm differential twin-ax wiring to date but various issues are pushing us to look at micro-coax as an alternative.  Our current hardware uses the DS90UB913/914Q devices.  Would it be feasible to use these parts for initial testing or must I use the "A" versions; ie, should the "Q" parts function but not be ideal or is it pointless without the "A" parts?  Our cable length is around 1 meter.

Thanks,

Carl Jackson

  • 0
    TI__Mastermind 20820 points

    Hi Carl,

    Somebody is looking into this and will respond shortly.

    Regards,

    Michael Peffers

    High Speed Interface Applications

  • 0 in reply to Michael Peffers
    TI__Expert 7395 points

    Hi Carl,

    It is not recommended to use the DS90UB913/914 for coax operation; but instead use DS90UB913A/914A. The DS90UB913A/914A chipset is electrically similar to the DS90UB913Q/914Q. The main difference is DS90UB913A/914A offers improved support for both coaxial cable and STP operation; whereas DS90UB913/914 is intended only for STP. Also note the minimum PCLK frequency is 10MHz and 25MHz for DS90UB913/914 and DS90UB913A/914A respectively.

    Dac Tran

    SVA APPS

  • 0 in reply to Dac Tran
    Intellectual 500 points

    Hi Dac,

    I understand the difference between the versions and that the "Q" parts are not intended for coax.  If I change my design to use micro-coax, I will certainly use the "A" parts.  But first I'd like to mock up the changes so my question is whether or not it is possible to use the "Q" parts at all assuming a short (< 1 meter) connection.  I only have two prototype board sets left to experiment with and I'm concerned my serializer board will not survive replacing the '913 with an "A" version.  I'd appreciate your guidance on this - I don't want to waste my time attempting to get the "Q" parts to work using micro-coax if it's known not to be feasible.

    Thanks,

    -Carl

  • 0 in reply to carlpii
    TI__Genius 13475 points

    Carl

    If you use the 'A' version parts, you will be able to use either coax or differential media, but with the 'non A' parts, only differential will work.   The parts are pin compatible, and the register maps are the same, so you should be able to easily try out the 'A' part with coax.

    Mark

     

  • 0 in reply to Mark Sauerwald88474
    Intellectual 500 points

    Ordered the 'A' version parts, being installed today.  There is one difference in the data sheets that I'd like to resolve before testing them.  The serializer MODE pin resistor value to select PCLK mode is listed as "0k" ohms for the original version and 100K ohms for the "A" version.  Searching the forum, it looks like the original data sheet is in error and it should always have been 100K ohms - is this correct?  I'm using 0 ohms in our current systems without apparent issues.  Should I be concerned?

    Thanks,

    -Carl

  • 0 in reply to carlpii
    TI__Genius 13475 points

    Carl

    You are correct - there was an error on the earlier datasheet which we caught and fixed on the latest datasheet for the 'A' version - the version that you get from the web should always be the latest version that we have.

    Mark

     

  • 0 in reply to Mark Sauerwald88474
    Intellectual 500 points

    Thanks Mark.  I used 100K in my initial testing of the 'A' parts with micro-coax and it appears to be working fine.

    I am concerned about our first production run built last December using 0 ohm resistors.  They are working now but could there be any long term issues?  Most don't have a lot of run time on them yet.

    -Carl