Thread Links Date Links
Thread Prev Thread Next Thread Index Date Prev Date Next Date Index

[802.3_4PPOE] Open Circuit Vdiff Test

Hi Yair, All,

I've attached a simulation of a Vdiff open circuit measurement which shows a 20mV Vdiff result for an internal current leakage difference of 10uA. The implication is that a series forward-biased diode feeding the PI can easily fail this conformance test unless it feeds both pairs of the same polarity through a common node.

Avoiding any forward-biased diodes which feed a single pair in 4-pair PSE designs may be the only practical means to consistently avoid this test failure. This would likewise result in better balance at high currents. However, some AC MPS and protection methods may be impacted by this, so a note in an Annex and perhaps removal of AC MPS in 4-pair designs might be warranted.

The above points probably do validate the omission of such PSE diodes from 4pr unbalance models, which is helpful.

Best Regards,

Attachment: PSE_Diodes.jpg
Description: JPEG image