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[802.3_10SPE] What should be specified in the standard for multidrop power

Hi All,


There is a discussion on what should be specified in the standard for multi-drop power in our adhoc meeting.   I start this email to follow-up that discussion.


First I believe multi-drop power system is an “engineered” system, if anyone has any use case that is not “engineered”, please share with us if possible.


Multidrop Engineered Power System is different from PnP PoDL point-to-point power system: One PSE will power multiple PDs, and PSE cannot detect/classify how much power that the PDs demand during the operation.


With these differences in mind, initial thoughts to specify power class for multi-drop are shared as follows:

1.       The worst case should be considered (maximum distance, maximum number of PDs and worst topology meaning all PDs lumping in the far end of the trunk cable)

2.       Trunk and Stub loop DCR should be specified for the worst cable we want to support

3.       Minimum PSE power capability (minimum output power) should be specified to ensure the enough power to be delivered to all PDs, “Vpse,min, Ipse,min” (in my original presentation, it says Vpse,min and Ipse,max, I think it is wrong because it tells the maximum output power of PSE)

4.       Minimum total power delivered to all PDS (Ppd,total,min) to guarantee all PDs get enough power

5.       Minimum voltage to PD’s power interface (Vpi) to guarantee all PDs can work under this voltage ( a far end PD with minimal input voltage should be considered)


Multiple power classes could be specified for different use cases (industrial automation, automotive, … ).


Please share your thoughts on this matter if you have, thanks!


Best regards


Dayin XU(徐达银), Sr. Research Engineer

Shanghai Research Center, Rockwell Automation

+86-21-61288390, dyxu@xxxxxxxxxxxxxxx