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

Re: [802.3_4PPOE] Finalyzing E2EP2P_Iunb/Runb , Ppeak_PD, Icut, ILIM



One area to be concerned about if peak-to-average ratios are reduced relates to how Type-3 / Type-4 PD’s will form power requests in LLDP.


For example, a PD that might have 10% power bursts for 10msec or less will be forced to form the LLDP Power Request based more on peak power than average power.    This in turn burns more power budget in the PSE.


No idea how many PD’s will fall into this category, but lower peak-to-average ratios assure that more PD’s will encounter this issue.



Pete J

Sifos Technologies


From: Yair Darshan [mailto:YDarshan@xxxxxxxxxxxxx]
Sent: Monday, June 08, 2015 12:08 PM
To: STDS-802-3-4PPOE@xxxxxxxxxxxxxxxxx
Subject: [802.3_4PPOE] Finalyzing E2EP2P_Iunb/Runb , Ppeak_PD, Icut, ILIM


Hi all,


I would like to have your opinion on the following plane:


We have numbers for ILIM_2P_MIN and ICUT_2P for Type 3 and 4.

ILIM_2P_MIN may reach to 1.2A for Type 4 and 0.875a FOR Type 3.

Technically we can work with this numbers.

These are worst case numbers based on worst case model and also the fact that we allow ripple current Ipeak, in the PD according

Practically I would like to reduce this numbers in order to reduce stress from transformers.


We have several ways:

1.       Reducing Ipeak by reducing the Ppeak_PD/Pclass PD factor from 1.11 for Type 3 to a lower value e.g. 1.07 range and for Type 4 to reduce it to ~1.03.

2.       Reducing PD Vdiff budget to lower value So E2EP2P_Iunb will be lower (this move has the highest effect)

3.       Using statistical analysis that will help reducing E2EP2P_Iunb (preferred to be our last move only after our spec is stable).


I prefer to start with 1 due to the fact that in reality, PD behavior has much less AC ripple that we assumed in 802.3at.

My goal is to reduce currents by at least 5%.


I'll appreciate your inputs.





Darshan Yair

Chief R&D Engineer

Analog Mixed Signal Group

Microsemi Corporation


1 Hanagar St., P.O. Box 7220
Neve Ne'eman Industrial Zone
Hod Hasharon 45421, Israel
Tel:  +972-9-775-5100, EXT 210.

Cell: +972-54-4893019
Fax: +972-9-775-5111


E-mail: <mailto:ydarshan@xxxxxxxxxxxxx>.