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TM4C1294NCPDT: Unconnected Ethernet PHY Pins

k ch
Prodigy 80 points
Part Number: TM4C1294NCPDT

Hello

We are using a customized board with TM4C1294NCPDT microcontroller.

We have several device variant. One with Ethernet, other variant without Ethernet. It means that PCB with Ethernet transformer may not be installed.

On page 1464 of Datasheet we have statement:

So I have such a question is it safe to use the MCU with the Ethernet PHY disabled option in this configuration:

  • 0
    TI__Guru*** 135355 points

    Hello k ch,

    So the question is if you can leave the 49.9Ohm resistors and power connections etc. still on the Ethernet pins but remove the transformer?

    FYI the datasheet says RBIAS can be excluded but an errata item addresses that in some cases you cannot so generally recommend to keep the RBIAS resistor connected still.

    Best Regards,

    Ralph Jacobi

  • 0 in reply to Ralph Jacobi
    Prodigy 80 points

    Thank you for your comment about Errata.

    Yes exactly, the question is can I leave the 49.9Ohm resistors but remove the transformer? Is it safe to use the MCU in this configuration?

  • +1 in reply to k ch
    TI__Guru*** 135355 points

    Hello k ch,

    It would be safe to use the MCU in that configuration, though I feel you'd save further BOM cost by removing the passive components as well.

    The recommendations we make are to minimize any potential leakage currents, interjections of noise, etc. - basically to make the design as robust as possible. But the configuration you describe wouldn't cause any problems at a device level.

    Best Regards,

    Ralph Jacobi