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[DP83867] Magnetics Connection

Takahiro Ogo
Genius 5940 points

Hi

I have a question about magnetics connections of DP83867.
I am looking at EVM schematic 　#DP83867ERGZ EVM: http://www.ti.com/lit/df/snlr034/snlr034.pdf

Acording to the schematic, the following is magnetic-connections.



 I wonder why Positive and Negative pins are reversed.
[DP83867] --- [TRANS] ------------[RJ45]
TD_1_P    ---  TD4-(Negative)
TD_1_N    ---  TD4+(Positive)

Are there any reason for this? My customer need to do such schematic design? (P and N pins have to be reversed?)
I think, either one is OK. Because this magnetic is not use for the voltage transformer but the isolation transformer and reduction EMI. Is my understanding correct?

Best Regards,
Taka

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5/31/18[LE]>unlock

  • 0
    TI__Mastermind 23675 points
    Hi Taka,

    The plus and minus on the transformer is to just make sure you maintain mutual inductance. Since the connections are consistent there is no issue. There would be issue is on one side of the magnetic it was plus to plus and on the other side plus to minus.

    For your customer I would recommend doing plus to plus and minus to minus just because it is cleaner to view and easier to understand and avoid confusion.

    Kind regards,
    Ross
  • 0 in reply to Ross Pimentel
    Genius 5940 points

    Hi Ross,
    Thank you for your reply. I got it.
    Excuse me, I have one more question about DP83867ERGZ EVM RJ45 Connection.

    I know that the EVM is using Mirror mode to connect to RJ45. So, I understand it makes reorder the port.
    A → D
    B → C
    C → B
    D → A

    However, The channel Polarity is reversed, too.
    For example:
      TD_1_P    ---  TD4-(Negative)
      TD_1_N    ---  TD4+(Positive)

    Can the Mirror mode revrese the "Channel Polarity"? Not only "Port"

    Best Regards,
    Taka



  • 0 in reply to Takahiro Ogo
    TI__Mastermind 19780 points

    *EDIT w/ new information*

    Hi Taka-san,

    Mirror mode changes the polarity and reorders the port numbers as well.

    Pin # (48QFN) Mirror Mode Disabled Pin Assignment Mirror Mode Enabled Pin Assignment
    1 TD_P_A (A+) TD_M_D (D-)
    2 TD_M_A (A-) TD_P_D (D+)
    4 TD_P_B (B+) TD_M_C (C-)
    5 TD_M_B (B-) TD_P_C (C+)
    7 TD_P_C (C+) TD_M_B (B-)
    8 TD_M_C (C-) TD_P_B (B+)
    10 TD_P_D (D+) TD_M_A (A-)
    11 TD_M_D (D-) TD_P_A (A+)

    This should not present an issue because DP83867, and all gigabit PHYs, automatically detects and corrects polarity of the channel. The polarity detection and correction feature does not have to be managed.

    Best Regards,

  • 0 in reply to Rob Rodrigues
    Genius 5940 points
    Hi Rob-san,
    Thank you very much for your kind support, always!

    Best Regards,
    Taka