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ZedBoard Hardware Design SDRAM Missing Pin
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Related

SDRAM Missing Pin

Former Member
Former Member over 13 years ago

In reviewing the Sept. 13 schematic I noticed that it appears as if pins F1 (VDDQ) and G7 (VDD) on the SDRAM are missing.  Also, I notice that T7 (NC) is listed as A14.  I understand that T7 may be used as A14 for another SDRAM chip, but why do F1 and G7 not appear on the schematic?

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  • bhfletcher
    0 bhfletcher over 13 years ago

    I see what you mean.  I am looking into this.

    Bryan

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  • bhfletcher
    0 bhfletcher over 13 years ago

    Thank you very much for your feedback.  On Rev C ZedBoard, pins F1 and G7 on the two DDR3 chips are No-Connects.  This is why they do not show on the schematic.  This is an error.  F1 should be VDDQ, and G7 should be VDD, both of which should attach to the DDR1V5 rail.

     

    I have asked Micron for a statement of impact and received the following reply:

    It will be somewhat dependent on the board layout. If the supply distribution is robust enough to the other pins, and the signal integrity is adequate, there may not be a problem.  Once the board is running I would not expect to see problems develop in the field.  As for long term reliability, I don’t think the lack of a power connection to those pins will lead to long-term failures (on-die metal migration, etc.), especially operating at 533MHz.

     

    We will correct this during our next board revision.  Any designer that is using ZedBoard as a reference should connect these pins.  However, we do not expect it to be a problem on the existing Rev C boards in the field.

     

    Bryan

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  • Former Member
    0 Former Member over 13 years ago

    Will all boards shipped at this point in time have these pins connected?

    Ron

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  • bhfletcher
    0 bhfletcher over 13 years ago in reply to Former Member

    We currently are shipping Rev C boards.  It will take us a few months to make the corrections and build up new stock with the changes made.  Therefore, we are shipping boards that do not have these pins connected.  However, we have not experienced any problems due to this issue.  We do not expect this to cause problems.

    Bryan

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