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Original question:

[FAQ] DP83867E: Ethernet PHY SGMII Vdiff Upper and Lower Input Limits

DP83867E: Issue with SGMII Signal Amplitude When Combined with Zynq Ultrascale+

Hiroaki Yamazaki
Prodigy 20 points
Part Number: DP83867E

Tool/software:

We are using the DP83867E in combination with the Zynq Ultrascale+.

The interface we are using is SGMII, and there are no issues with normal communication.

However, when we apply static electricity, the link is lost, and the value at PHY address 0x0013 appears to be 0x0504 at that time.

We suspect an SGMII error and observed the SGMII signals with an oscilloscope.

The differential amplitude of the output from the Zynq was around 600mV, whereas for the DP83867E, it was about 300mV or less.

Is there a way to increase the amplitude of the SGMII output from the DP83867E?

  • 0
    TI__Mastermind 19885 points

    Hi Hiroaki-san,

    When you mention you add a static electricity. Are you trying to perform an ESD test? 

    If possible, may I ask where is the point of injection and what test customer is performing? Is it IEC61000 4-2?

    Does the link recover after you apply the static electricity?

    --

    Regards,

    Hillman Lin

  • 0 in reply to Hillman Lin
    Prodigy 20 points

    Hi  Hillman-san,
    Thank you for your response.

    Yes, we are trying to perform the IEC 61000-4-2 ESD test. The injection points are contact discharge to the screw on the side where the Ethernet connector is located, as well as air discharge to that surface.
    The link sometimes recovers, but sometimes it does not. When the link does not recover, any attempt to read the PHY registers results in a response of 0x7949.
    What’s worse is that the link can sometimes drop just by charging the ESD gun about 5 cm away from the EUT.


    There are only 100nF AC coupling capacitors on the SGMII differential signals, and there are no 100Ω termination resistors implemented externally on either the Zynq side or the DP side.

    Best Regards,

    Hiroaki Yamazaki