DP83869HM: Trace length

Hi Rubigaa,

MII traces need to be less than 6 inch/6000mil and MDI traces have to be less than 2000 mils.

Please refer to this app note for more detail: https://www.ti.com/lit/an/snla387/snla387.pdf?ts=1755481624530&ref_url=https%253A%252F%252Fwww.bing.com%252F

Best,

J

Hi J,

We are configuring PHY in RGMII mode and operating at 100Mbps. Can you please provide the length specifications?

Regards,

Rubigaa

Hi Rubigaa,

Same length specifications apply for RGMII at 100Mbps.

6 in for RGMII and 2 in for MDI side of the trace.

Best,

J

Hi J,

Thank you for the provided details. It was not feasible to maintain a 2-inch trace length on the MDI lines between the PHY and the RJ45 jack in our design. So, we have revised the routing plan to include ~2 inches between the PHY and the magnetics, and <1 inch from the magnetics to the RJ45 connector. Kindly confirm if this approach is acceptable.

Regards,

Srikanth Kacchu

Hi Srikanth, 

The 2-in trace length recommendation in the application note is a rule of thumb. This is to minimize signal integrity degradation and minimize parasitic. We do not expect sudden degradation of signals because the MDI trace is longer than 2 inches, but there may be some signal quality degradation. 

Best,
J

Hi J,

Thanks for the details. Could you please suggest an RJ45 connector with integrated magnetics?

Regards,

Srikanth Kacchu

Hi Srikanth, 

Unfortunately, we do not give integrated magjack recommendation. We only have discrete transformer recommendation which is Pulse HX5008NL. 

Best,
J