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Re: [802.3_4PPOE] PD Load turn on



The phrase


The turn off voltage Voff applies both during power on and after power on”


might be better using the term “power up” rather than “power on” because that is the PSE state machine inrush load state where sub-30V foldback can kick in.



Pete J



From: Koussalya Balasubramanian (kobalasu) [mailto:kobalasu@xxxxxxxxx]
Sent: Thursday, February 26, 2015 2:09 PM
To: STDS-802-3-4PPOE@xxxxxxxxxxxxxxxxx
Subject: [802.3_4PPOE] PD Load turn on




In Jan interim meeting, Jean and I presented about clarifying PD load turn on behavior that will help in making sure non-compliant behaviors are avoided.  The team directed us to submit this as a maintenance request.  Here is what we are planning on submitting – given the maintenance request will come back to 4PPoE group, we would appreciate any comment from 4PPoE group before we submit it.


Problem Statement:  

- PDs in the field turn on their Load during Inrush.  This leads to PD cap not charging up fully (even if C<180uf and PSE is following inrush rules from  This may lead to operational problems after inrush.  There is a Voff requirement in PD table 33-18 to ensure power supply remains turned off for V<30V, but customers seem to read this as applicable only "after power on" not during "power on" - hence they turn on their DC-DC during inrush causing problems.


Suggested Solution

Add the following to section

"PDs shall not draw more than the maximum current allowed by a PSE during inrush as outlined in section"

Add the following to section at the end of second paragraph.

"The turn off voltage Voff applies both during power on and after power on"