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AM623: Questions about DDR4 layout on AM6234.

xu.dengke
Prodigy 90 points
Part Number: AM623

Two questions are as follows:

1.If it's necessary to satisfy the meets of SPRAD06(AM62x DDR Board Design and Layout Guidelines) for single DDR4 connenction?I noticed that this document limit the signal length and other limitations blow:

Table 2-6&Table 2-7.

But,puzzlingly,the "A3" mentioned is for two SDRAMs,we just use one DDR4 in our case,so,shall we follow the limitations listed in this two table?If follow this ,we will ignore the "A3" segment.

2.The next question is that it's too short to satisfy the meets of "AT" length,I notice that it's just a typical value in the Table 2-6,so,is there a max limitation for AT length?

Thank you~

Hoping for your reply soon~

  • +1
    TI__Guru* 86970 points

    1. yes, you can disregard A3 trace if it is not a part of your design

    2. There is no max, but length AT should be kept as short as possible

    Note that if you only have one DDR4 device with only one load on the addr/ctrl signals, then VTT termination is not required (an update to the appnote to reflect this is pending).  Thus you wouldn't need to worry about AT length.

    Regards,

    James