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DP83867 layout question

Genius 4735 points

Replies: 4

Views: 1816

Hola,

We follow up TI DP83867 reference design to plan the layout phase but we had met a problem about RJ45's DM、DP layout trace overlap/crossover issue!

After that, we had found the document of snlu190 and dp83867_circuit, its layout of RJ45 is very smoothly as below figure.(pg3 & pg12)

snlu190.pdf

dp83867_circuit.pdf

But its connection method of DM & DP are all different, you can observe that J13 & J4 were be connected to the different pin out.

Ex:J4'spin1 and pin2 were connected to T1's pin13 and pin14 but J13's pin7 and pin8 were connected to T1's pin13 and pin14.

Are these connection method for let layout can be smoothly?How can I do that can let DP & DM layout smoothly to avoid overlap/crossover?

Or it can internal adjust by the software setting?

  • Hello Jacky,

    If you are having a problem with traces crossing over on your design, you may benefit from using "mirror mode". You can read about this in section 9.4.6.7 of the DP83867E datasheet.

    Mirror mode lets you reorder the channels on the PHY. In the case of the J13 example above, PHY TD pair 1(A) is going to pair 4(D) on the RJ45. That configuration requires the use of mirror mode.

    Best Regards,

    Rob Rodrigues

    CTS (Clock & Timing Solutions) Systems Engineer

  • In reply to Rob Rodrigues:

    Hola Rob,
    Thank you very so much.
  • In reply to Rob Rodrigues:

    The mirror mode pair swapping is described well in the data sheet.  A->D and so on.  

    Polarity swapping is not mentioned.

    Examining the DP83867ERGZ reference design it looks like polarity swapping is supported Ap->Dn, An->Dp.

    Can you verify that the pairs and the polarities are swapped in mirror mode?

  • In reply to Barry W:

    Hi Barry,

    Yes, with mirror enabled, the polarity detection and correction will work.
    Ap -> Dn, An -> Dp, etc... are valid cases for the DP83867.
    You will just need to ensure mirror is enabled.

    Kind regards,
    Ross

    Best regards,

    Ross Pimentel

    Ethernet - Applications Engineer

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