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Re: [802.3_4PPOE] IEEE802.3bt - End to End Channel Pair to Pair Resistance Unbalance Adhoc - Meeting #8 material

Hi Ken,

Many thanks. I have quick review on this. I saw some issues/questions that I will discuss with you over the reflector to save the meeting time.

The issues are:

Channel P2PRUNB is too low. Not possible. We will discuss why at the meeting in my presentation.

PD unbalance: Numbers make sense, if we can have lower numbers it will be better and I may have idea how to achieve it.

PSE unbalance too low. It is not practical. The Rmin requirement is OK. I am suggesting too 0.1 ohm at least. Rmax is too low, not practical. Just consider Rdson variations. Please follow the database table of our working numbers and then let's talk about it.

Many thanks for your efforts.



From: Ken [mailto:ken_bennett@xxxxxxxxx]
Sent: Tuesday, June 24, 2014 6:33 PM
To: Darshan, Yair; STDS-802-3-4PPOE@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_4PPOE] IEEE802.3bt - End to End Channel Pair to Pair Resistance Unbalance Adhoc - Meeting #8 material


Hi Yair,
In response to your request for calculated examples below I've attached a spreadsheet which can be easily modified for worst case Model values. 
PSE Rmax limit is calculated using the derived equation and PSE Rmin.  The table on the right shows results for a range of PSE Rmin values.
Best Regards,

On 6/23/2014 6:06 PM, Darshan, Yair wrote:

Hi Ken,

Thanks, Please see my comments. I'll appreciate if you can address it prior the meeting so we can save time.

Slide 2: Please use the ad-hoc Acronyms as agreed on Annex J1 page 60 at the ad-hoc material. I am referring to bullet 2 when you say "P2PRunb". Do you mean End to End P2PRunb ?

The End to End P2PRUnb is system requirement that will generate eventually the current unbalance in addition to voltage unbalance PSE and PD. This parameter will not be in the spec. It is a guide line or "system" spec to us.

The parameters that will be specified are:

PSE PI  Resistance and voltage unbalance.

PD PI Resistance and voltage unbalance.

Channel P2PRUNB.


Slide 3: No comments. It is correct. Furthermore I am going to propose to specify minimum resistance to PSE PI and PD PI per my presentation conclusions sent to the reflector and to the team regarding the channel use case analysis results. This is I believe supported and resolve the last two bullets in this slide.


Slide 4: I like the direction. It supports slide 3. It is also similar to the analytical way that I have shown in the last adhoc meeting (on slide 14 of our next meeting material) which is:








I understand that the Kpd part and Kch part was merged to Y term. Is this correct?


Slide 5. Looks good. Please show equation derivation to justify the method. It will helps also to those who interested to use it and run simulations to test the concept.

Slide 6:

3rd bullet not clear. (Don’t otherwise provide a balancing technique)

5th bullet: Why "4 pair powering shall be sourced from a single DC supply" is Important if Voltage difference is specified?

Bullet 6: It is implementation issue. We cannot require it. You need to translate your intention to voltage, resistance, current to allow/disallow what you believe is best and we can discuss it.

Bullet 7: Yes agree. I am proposing the same for PSE and PD i.e. to specify Rmin.

Annex – derivation of equations: Please supply next meeting calculated examples so we can verify in simulation. Please use only adhoc numbers so we can use the same data base and Christiam and me can both check it.

Example at the last slide: The point is clear. Please use the adhoc data base from the same reasons above.


Many thanks



From: Ken [mailto:ken_bennett@xxxxxxxxx]
Sent: Monday, June 23, 2014 9:21 PM
To: Darshan, Yair; STDS-802-3-4PPOE@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_4PPOE] IEEE802.3bt - End to End Channel Pair to Pair Resistance Unbalance Adhoc - Meeting #8 material


Hi Yair, All,
I've attached a new revision of the slides for the meeting.
Best Regards,

On 6/22/2014 8:03 PM, Darshan, Yair wrote:


Hi all,


Please find meeting material for Tuesday June 24, 2014. The focus is planned to be on slides 6-10, 13,14, 16-30.

I'll appreciate if you review the slides per the agenda prior the meeting.


Ken: You are scheduled to present your material from last time. Please resend it to the reflector/team.







Darshan Yair


Power over HDBaseT Subcommittee

HDBaseT Alliance


Chief R&D Engineer

Analog Mixed Signal Group

Microsemi Corporation


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