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DP83826E: Inquiry due to EMI failure of DP83826 application board

Grady Lee
Genius 4215 points
Part Number: DP83826E

Tool/software:

Hi, TI expert

The EMI test of the board with DP83826 applied by the customer has failed.

Regarding the EMI test, we would like to inquire about the cause and possible solution.

The customer confirmed that there was a problem where the specifications were exceeded in the 400KHz~1MHz band.

They tried using shielded cables instead of traditional UTP cables, and while there was some improvement, there was no significant change.

I am attaching the circuit diagram and PCB drawing for your reference.

Ethernet_schematic.PDF

LAN_EMC_PCB.pdf

Q1) Have you had a similar case? Are there any possible causes and solutions to EMI problems? Is there anything I can refer to to solve EMI?

Please check. Thank you.

  • +1
    TI__Mastermind 24998 points

    Hi Grady,

    Which EMI standard / test is being performed by customer? Can pictures of the test setup be shared?

    I recommend referring customer to this application note for optimizing test setup, schematic, and layout for EMC/EMI performance depending on the test:

    https://www.ti.com/lit/an/snla466a/snla466a.pdf

    Thank you,

    Evan

  • +1
    Prodigy 140 points

    Hi Grady,

    Not a TI employee, just a regular engineer.

    Been trough EMC hell a number of times, I would recommend you acquire and read this book:

    Electromagnetic Compatibility Engineering
    Author(s):Henry W. Ott
    First published:12 August 2009
    Print ISBN:9780470189306 |Online ISBN:9780470508510

    https://onlinelibrary.wiley.com/doi/book/10.1002/9780470508510

    And start by reading Annex B, D and chapter 18.

    These were the most helpfull readings I know of.

    As for the specific problem at hand, it will require much more measurements (along cables, directional probes, turning certain section on/off to narrow down the causes).
    The layout of the board, how it is attached to the casing, the cabling and all the associated hardware will need to be reviewed.

    I am afraid TI will not be of much help here, as it's not a silicon issue, but an integration/design one.