The following section mainly go over the general guideline on how to debug EMC issue on DP83867PHY.

• Check the test setup:

  EMC test:

  • No loop cable
    
  • Place the cable away from the emission source or Antenna (mainly on RE test)
  • Shielded cable is preferred
  • Make sure the test board and test equipment match (mainly on CE test)
    • Cable type needs to match the CDN test equipment
  • Turn off CLK_OUT when it is open or not used
  • EMI test:
    • Check the ground path of both test board and test equipment
    • Shielded cable is preferred
    • Make sure the cable type match with test equipment (mainly on CI test)
      • Cable type needs to match the CDN test equipment

• Check the schematic
  • Make sure there is a ground isolation

    Make sure there is a ground isolation path (R//C) between connector ground and earth ground

    Make sure the Transformer follow data sheet specification

    No shorted center taps on transformer

    Double check on the capacitors on the center taps of transformer

    Remove ESD diodes on MDI lines for compliance test

    Check Rbias value and make sure the value falls in the 1% range

    Follow the schematic check list recommendation in Section 2.2

• Check the layout
  • Make sure no clock signal and data signal near the MDI lines
  • Check length matching and impedance matching for MDI lines
  • No vias around the MDI lines
  • Follow the layout checklist in Section 2.2
• If customer is struggling on conducted immunity IEC61000 4-6 on DP83867 PHY, please program the following script:

  • begin
    008A 010F 
    00C0 0000
    00B3 000C
    0100 1027
    001F 4000
    end

These registers tune the filter inside the PHY to further optimize and filter out high frequency noise and improve the Signal to Noise ratio.