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MGT track lengths for carrier SFP ports

mark.hosey@dtaq.co.uk

I'm working on a carrier design for a PicoZed p/n AES-Z7PZ-7Z015-SOM-G/REVE.

My boss handed me a PicoZed file titled PBA-PZ2SOM.PCBDOC that lists all net track lengths between the Zynq and the PX connector. He has no recollection of where this file came from. In it, all of the MGT signal pairs have a difference in length between the P and the N tracks ranging from -13.259mil to + 37.22mil.

Now, the PicoZed carrier design guide stipulates that all gigabit transceiver signals within a single pair (P and N) shall be length tuned to within 25 mils of each other (P to N).

In the aforementioned document there is a 37.22 mil difference between MGTRX0_P and MGTRX0_N. Bearing in mind the carrier design guide stipulation above this track length difference is significant.

My questions are:

1) Do you have any idea of the legitimacy of the document my boss handed me?

2) If it is ligit does it apply to AES-Z7PZ-7Z015-SOM-G/REVE?

 

If 1 is yes and 2 is no, then:

3) Is there a version of the document that does apply to AES-Z7PZ-7Z015-SOM-G/REVE?

 

If 3 is yes

4) Where can I obtain it from?

 

and if the document is ligit:

5) When designing SFP ports for the a carrier PCB must I take into account these published track length differences on the SOM to meet with the carrier design guide stipulation?

 

Regards,

 

 

Mark Hosey

 

  • 0

    OK.

    I've since found a document "Net status - PBA-PZ2SOM Rev E on this forum.

    So its a legit doc and this is the one I should be referring to.

     

    So my last question still stands:

     

    5) When designing SFP ports for the a carrier PCB must I take into account these published track length differences on the SOM to meet with the carrier design guide stipulation?

     

    Regards,

     

    Mark

  • 0 in reply to mark.hosey@dtaq.co.uk

    Hi Mark,

     

    In regards to the file PBA-PZ2SOM.PCBDOC you have. There is no way to tell if this is a final released file without examining it, but it is a proprietary file that should not have been distributed beyond Avnet and companies with paid IP licenses. Unless your company has a signed license agreement please delete the file and any others in the set and ask your boss to do the same.

     

    You should not require the SOM files to create a carrier card, you can trust the signals are matched as stated in the carrier design guide. Please follow the guide lines in the PicoZed Carrier Card design guide.

     

    Thank you,

    Josh

  • 0

    Thanks for your reply Josh.

    I can now go ahead with my design ensuring the SFP net lengths on my carrier design conform with the carrier design guides stipulation without regard to the PicoZed net lengths file.

     

    By the way, the file I was given is a copy of the (apparently) freely available "Net status - PBA-PZ2SOM Rev E" which is already posted and available for download on this forum. (Perhaps it shouldn't be?)

     

    Mark

  • 0 in reply to jafoste4

    Thanks for your reply Josh.

    I can now go ahead with my design ensuring the SFP net lengths on my carrier design conform with the carrier design guides stipulation without regard to the PicoZed net lengths file.

     

    By the way, the file I was given is a copy of the (apparently) freely available "Net status - PBA-PZ2SOM Rev E" which is already posted and available for download on this forum. (Perhaps it shouldn't be?)

     

    Mark

  • 0 in reply to mark.hosey@dtaq.co.uk

    Hi Mark,

     

    If the file you have is the same as "Net status - PBA-PZ2SOM Rev E" then it is fine. The name of the file you have labeled PBA-PZ2SOM.PCBDOC refers to the PCB layout source of the SOM board according to my information on our end, not only the Net Lengths.

     

    I would prefer if you would delete the file named PBA-PZ2SOM.PCBDOC, and use the file Net status - PBA-PZ2SOM Rev E for your design.

     

    I believe you also have the source files for the PicoZed FMC V2 you may also use as a board layout reference.

     

    Thanks,

    Josh

  • 0 in reply to jafoste4

    Also for your reference, this can be viewed in the Hardware User Guide for the PIcoZed 7015/7030.

    "The boards trace lengths are matched, compensating for the internal package flight times, to meet the requirements listed in the Zynq-7000 AP SoC PCB Design and Pin Planning Guide (UG933)."

     

    Thanks,

    Josh