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Re: [802.3_4PPOE] Slide 7



Hi Jeff,

Please see my response below.

Yair

 

From: Jeff Heath [mailto:jheath@xxxxxxxxxx]
Sent: Wednesday, July 02, 2014 6:30 PM
To: Darshan, Yair; STDS-802-3-4PPOE@xxxxxxxxxxxxxxxxx
Subject: RE: [802.3_4PPOE] Slide 7

 

Yair,

 

See my response below. 

 

Regards,

 

Jeff Heath
Design Center Manager

Description: Linear Technology Corporation

 

 

paper:

402 East Carrillo Street, Suite D

 

Santa Barbara, California 93101

voice:

805.965.6400

fax:

805.965.1701

computer:

jheath@xxxxxxxxxx

 

www.linear.com

 

 

From: Darshan, Yair [mailto:YDarshan@xxxxxxxxxxxxx]
Sent: Wednesday, July 02, 2014 5:00 AM
To: Jeff Heath; STDS-802-3-4PPOE@xxxxxxxxxxxxxxxxx
Subject: RE: [802.3_4PPOE] Slide 7

 

Hi Jeff,

Please see my response below.

Thanks for communicating all these questions over the reflector.

Regards

Yair

 

 

 

From: Jeff Heath [mailto:jheath@xxxxxxxxxx]
Sent: Tuesday, July 01, 2014 11:02 PM
To: STDS-802-3-4PPOE@xxxxxxxxxxxxxxxxx
Subject: [802.3_4PPOE] Slide 7

 

Yair,

 

On slide you again say that the PD PI needs to be better than the PSE PI despite the objections noted in the previous meeting. 

Yair: You are correct, I have already changed it but I didn’t send it together with other updates due to lake of time. The following is what you will see in the next adhoc slides.

-------

  • " Channel capable of regulating/reducing of end to end unbalance as function of channel length.

 

JLH:  This implies an active balancing circuit.  We are far from having the data or discussion on this topic.

Yair: How you can interpret that channel can regulate so it is active. This is the channel it is cable and connector. Please think about it.

The meaning of regulate is if the channel P2PRUNB is X and PSE and PD PI is Y and Y>X so X reduces Y , than Channel regulate Y. Simple.

--

  • PD PI and PD PI need to be better than the channel maximum P2PRUNB.

JLH:  It is unclear what you mean and it is a conclusion without discussion.

Yair. This is conclusion that not need discussion, after working on it over a year. The guys that work on this understand and agree to it.

--------------------

  • PSE PI and PD PI needs larger unbalance range to allow different implementations (TBD)

JLH:  It is unclear what you mean and it is a conclusion without discussion.

Yair. This is conclusion that not need discussion, after working on it over a year. The guys that work on this understand and agree to it.

Yair: Jeff, please follow the work already done and al lwill be clear to you.

Please let me know if it is OK for you now.  

-----

Specifically to what we know so faron the subject:

-Since in first meetings we agree that the PD is dominant in setting the pair to pair current especially the diode effects, we would like to give the PD flexibility in a way that we will not have to add components to PD and also support Type 1 and 2 PDs that are already in the field.

JLH:  The PD component changes are not decided by the bt Task Force

Yair: The fact that component is changes, will not change this conclusion. Do the sensitivity analysis and you see it.

-The PSE on the other side has different implementations. You can see it by using the current numbers in the data base table in which you create combinations possible resistances in positive rail, negative rail and the mix between them.

JLH:  Both the PSE and the PD will likely change.

Yair: So what? It will change anything?

-The question which should be higher, I need to finalize my research in order to be sure

Could create a presentation to show why you come to this conclusion.

Yair: Yes I will although we discuss it already few IEEE meetings ago in our presentations.

I will not have time to  put presentation for it for July however I suggest that you will do it so we can decide on this point.

JLH: Yair, you are the one suggesting the solution, you should create a presentation outlining why.

Jeff, you have to do some work here. We show it in our model and when Christian did his sensitivity analysis. We can't go a back and in many discussions.

There are a lot of work we did and will do. If something is not clear to you work on it too to and challenge us or me. This will be real contribution to the adhoc.

-----

 

IF anything, the PSE is much easier to balance (if one does not use AC MPS.)  The standard PD implementation has diode bridges which in the short channel case (at least), are currently thought to be the largest contributor to overall current imbalance.

Yair: I agree with you in principle, but in order to be sure we need to set a list of PSE use case, analyze it and set the conclusions in similar what I am trying to do with the channel use cases.

JLH:  Yes, I strongly agree we need to focus on uses cases first, especially for the channel to start off.  This should be our highest priority.

Yair: The channel I hope will be done soon. I work on it for long time and we know what we need to know. I hope to close this issue with a motion at the July meeting.

----

In short, in the worst case PSE implementation (using AC MPS diodes) twice as many diodes as the PSE which directly opposes the conclusion you have arrived at.

Yair: You may be correct. But we need to follow the way suggested above so we will have records justifying our decisions. Sine you presented yesterday the MPS case, you can generate more use cases, eg. What will happen in 100BT systems and then we will see where it goes. Then we will know for sure. I am mentioning it since I am not sure you cover all use cases (thos you familiar with and those you don’t and you may need to ask for inputs about it)

JLH:  I intend to continue to simulate the agreed upon use cases.

-----

Regards

Yair

 

Regards,

 

Jeff Heath
Design Center Manager

Description: Linear Technology Corporation

 

 

paper:

402 East Carrillo Street, Suite D

 

Santa Barbara, California 93101

voice:

805.965.6400

fax:

805.965.1701

computer:

jheath@xxxxxxxxxx

 

www.linear.com