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Re: [802.3_4PPOE] PD Load turn on

Kousi, I recall that Dan Dove had an elegant solution that required the addition of one word. Unfortunately I can’t find that I wrote it down and the exact sentence escapes me. Maybe Dan remembers? 

Chad Jones
MGR, HW ENG, Cisco Systems
Chair, IEEE P802.3bt 4PPoE Task Force


From: "Koussalya Balasubramanian (kobalasu)" <kobalasu@xxxxxxxxx>
Reply-To: "Koussalya Balasubramanian (kobalasu)" <kobalasu@xxxxxxxxx>
Date: Thursday, February 26, 2015 at 2:09 PM
To: 4PPOE Reflector <STDS-802-3-4PPOE@xxxxxxxxxxxxxxxxx>
Subject: [802.3_4PPOE] PD Load turn on

Team

 

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 33.2.7.5).  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 33.3.7.3

"PDs shall not draw more than the maximum current allowed by a PSE during inrush as outlined in section 33.2.7.5"

Add the following to section 33.3.7.1 at the end of second paragraph.

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


Thanks
Kousi