We are experiencing an intermittent PHY link connection on a W6100 design.
Not all products show the issue but a good percentage do show the fault.
It is dropping the link when the ethernet is connected but also incredibly will sometimes show a valid link when no cable is connected.
Our software is monitoring the PHYSR register and then correctly reporting the Link status which was additionally verified by monitoring Pin 17 LNKn Link status LED.
Therefore, we do not think it is a software/configuration related issue as pin 17 is showing the “bare metal” LINK status.
We are at a loss as to how the W6100 can see a valid carrier signal with no cable connected and indicate a valid LINK on pin 17.
If this can be solved then hopefully that will also resolve the link dropping during normal operation but that is a guess at this stage.
What we have tried,
- Monitoring pin 17 which shows the issue
- We added the “bob smith” termination 75Ohm/1nF on the cable side of the magnetics between L555 and P551 with no effect.
This was to get as close to the reference design as possible
- The PCB layer stack is impedance matched. The traces are also very short so we are struggling to see this being the issue.
- The ethernet magnetics are from Link-PP and look suitable for the application
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Any assistance would be greatly appreciated.