Please see below.
Making a new paragraph does absolutely nothing to the requirements.
If anything, those 3 sentences all deal with the same topic: transients of various lengths, and should be one paragraph.
Yair: This is my point. They should be on the same paragraph but they don’t…
We're past the point we should be making such changes.
Yair: Agree but we did pass this point many times and this fix will not delay us.
I've the feeling there is a subsurface misunderstanding happening, there is no other explanation for so many emails over this topic.
Yair: The fact is that some people read the text and it raises questions. The fact that it is clear to some of us in the group, doesn’t make it clear to other
readers that were not part of the process.
Here's what 145.2.10.3 REQUIRES:
(1) Transient of longer than 250uS ==> voltage SHALL meet VPort_PSE-2P for the entire duration of the transient
(2) Transient of 30-250uS ==> voltage SHALL not go below VTran-2P at any time
Yair: So far all is good.
(3) Transient of 30us or less ==> voltage MAY fall below VTran-2P
Yair: Yes we know voltage may fall below Vtran-2P. But what are the requirements associated with it? No requirements? Keep port ON? What?
I list (3) even though it is not a requirement.
Yair: Agree that in (3) there is not requirement since I know the intent and why we did it in 802.3af but in 802.3bt we did two changes that make a difference:
-
We specify a requirement in the PD side for transients <30usec. So it is expected to address the PSE in that range.
-
We move the text in (3) to a new paragraph which may imply that we start a
“requirement process” but this process was not completed.
That is why I am suggesting to append the 2nd paragraph where (3) is located to the 1st paragraph where (1)+(2) are.
All this statement does is reinforce that we specifically choose not to make any requirement on the PSE for this particular case.
Yair: This is your interpretation. My interpretation is that what you are saying is true only if you append 2nd paragraph to the 1st
paragraph.
There is nothing broken here, hence the resistance to make changes.
Yair: There is nothing broken here..maybe, but there is something not clear here..for sure.
I would suggest we don't make any changes here.
Yair: I suggest to append the text of (3) to the text of (1)+(2) as in the 802.3af.
On Thu, 2018-06-14 at 18:23 +0000, Yair Darshan wrote:
Hi Chad,
I thought about this comment and I am proposing simpler solution that in my opinion will be good enough.
Currently the text looks like this:
“A PSE shall maintain an output voltage no less than VTran-2P
for transient conditions lasting more than 30
μs and less than 250
μs, and meet the requirements of 145.2.10.9.
[SPACE]
Transients less than 30
μs in duration may cause the voltage at the PI to fall below VTran-2P.
See 145.3.8.6 for PD transient requirements. Transients lasting more than 250
μs shall meet the VPort_PSE-2P
specification.”
The problem is if I read the above text:
I see a clear requirement on the first paragraph addressing the requirements for 30usec-250usec.
The second paragraph starts with informative text regarding transients below 30usec that invite the question
“OK what to do with it, what is the requirement”
and then you have again a clear requirement for behavior above 250usec.
If I make small editing change such as follows (append both paragraphs):
“A PSE shall maintain an output voltage no less than VTran-2P
for transient conditions lasting more than 30
μs and less than 250
μs, and meet the requirements of 145.2.10.9. Transients less than 30
μs in duration may cause the voltage at the PI to fall below VTran-2P.
See 145.3.8.6 for PD transient requirements. Transients lasting more than 250
μs shall meet the VPort_PSE-2P
specification.”
Now if I read this:
I see 1st requirement. Clear informative part. 2nd requirement.
What is your inputs on this proposal?
Does it make sense that it is simple change just remove space and merge both paragraphs so it will not look like two different paragraphs that the 2nd
one starts new requirement which is not the intent.
Yair
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>.
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