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Unused SGMII pins

srinivasaprasad saladi
Intellectual 295 points

Other Parts Discussed in Thread: TMS320C6678

Hi,

Iam using EVM c6678 as reference for schematic development for my card.

Iam removing AMC interface in our schematic.Ethernet interface remains same.
 SGMII1 is used for ethernet we are going to use same as per EVM schematic.
SGMII0 is used for AMC, As per hardware design guidelines document unused SGMII RXP RXN TXP TXN should be left floating.

I am  confused as these are high frequency signals if we leave floating leakage current will be high, Can we leave floating or we need to pull down or pullup these pins?.

Thanks & Regards,

SrinivasaPrasad.

  • 0
    TI__Guru* 84110 points

    SrinivasaPrasad,

    Please follow the Hardware Design Guide.

    7.4.4 Unused SGMII Pin Requirement
    All unused SGMII pins must be left floating. As an additional note, should the SGMII
    interface not be required; the peripherals should be disabled. In the event only one of
    the two SGMII interfaces is required, the unused SGMII interface must be disabled
    through the MMR of the device.

    Regards,
    RandyP

  • 0 in reply to RandyP
    Intellectual 295 points

    Hi Randy,

    Thank you for answer. If i disable SGMII /AMC in MMR and pins left floating ,  leakage current in these pins is negligible or considerable?

    Thanks & Regards,

    SrinivasaPrasad

  • 0 in reply to srinivasaprasad saladi
    TI__Guru* 84110 points

    SrinivasaPrasad,

    For best board design, you must follow the guidelines in the HW Design Guide.

    If the leakage would be "considerable", we would have different recommendations. "negligible" and "considerable" are both subjective terms that I cannot address (I do not know the leakage current). Instead, you may refer to the power estimation spreadsheet found on the TMS320C6678 Product Folder under More Literature.

    Regards,
    RandyP