Christian: I think that it would
be prudent to wait for TIA TR-42 and UL to come back with recommendations
on the maximum current(s) in single
cables and bundles before debating the current limit(s).
You may be all debating limits above
operating conditions deemed safe by experts in that field.
Best Regards
P.S Frankly the current limits
this TF is discussing concern me.
When I look at the way big bundles of
CAT5/6 are crammed into some buildings,
Imagining all of them carrying the maximum
current supplying Powered Devices,
leads me to a "Hindenburg Scenario"
or "Tacoma Narrows Bridge Syndrome"
caused by all those videos I was forced
to watch in Engineering Classes with
the not so subtle message: This is what
happens when engineers screw up.
Maurice Reintjes
MindspeedTM
Hillsboro, Oregon,USA
Office Phone (503)-403-5370
Mobile (503)-701-0797
Christian BEIA <christian.beia@ST.COM> Sent by: owner-stds-802-3-poep@ieee.org
06/26/2007 09:07 AM
Please respond to
Christian BEIA <christian.beia@ST.COM>
To
STDS-802-3-POEP@listserv.ieee.org
cc
Subject
Re: [8023-POEP] IEEE 802.3at Vport ad
hoc meetings Tuesday June 26; materials
Hi all,
If the PD has to limit the DC current at
720mA max, there would be a hard current limit in the hot-swap of the PD
chip at a lower level, let's say 700mA.
This means that there will be less than
30W available for the device, (700mA x 41V = 28.7W).
I think that we should put the PD DC current
limit above 720mA, to be sure the whole available power is supplied to
the load.
Thank you
Christian
From: owner-stds-802-3-poep@ieee.org
[mailto:owner-stds-802-3-poep@ieee.org] On Behalf Of Anoop Vetteth
(avetteth)
Sent: Tuesday, June 26, 2007 5:10 PM
To: STDS-802-3-POEP@listserv.ieee.org
Subject: Re: [8023-POEP] IEEE 802.3at Vport ad hoc meetings Tuesday
June 26; materials
Hi Yair
Some more comments on your presentation:
- Rather than having PSE Ilim_min
= PD Ilim_max + 1mA; I think it will be a cleaner solution to increase
the Tlim_min for PSE from 50ms to 51ms (or 55ms to make it a round figure).
My third point will make it clear why I like this approach (This makes
energy based policing easy).
- I do not like the term Ilim_min
for PSE. The whole reason why we have current limiting at PD is so that
we do not have to do current limiting at the PSE. We need to come up with
a better name.
- In 802.3af we had Ilim_min/Icut_min
= 14.28%. There is no rational reason why we need to keep this ratio the
same for 802.3at. We have much more advanced processes today.
We need to come up with the minimum
PD Ilim_max that is acceptable to everyone. There is also no reason why
we need to specify that there be a maximum duty cycle of 5%. Even if we
impose this, it is highly unlikely that a PSE is going to check for 5%
dutycycle over 1s. All we care is the threshold and average current.
If the PD draws
more than Iport_dcmax (720mA) for more than 51ms (or 55ms) then the PSE
can shut off the PD. There is no averaging involved here. This is a hard
threshold as in AF - Icut/Tcut
If the average current
drawn by the PD over 1 second is greater than Iport_dcmax (720mA) then
the PSE can shut off the PD.
Thank you
Anoop
From: owner-stds-802-3-poep@ieee.org
[mailto:owner-stds-802-3-poep@ieee.org] On Behalf Of Yair Darshan
Sent: Tuesday, June 26, 2007 4:22 AM
To: STDS-802-3-POEP@listserv.ieee.org
Subject: Re: [8023-POEP] IEEE 802.3at Vport ad hoc meetings Tuesday
June 26; materials
Hi Fred,
Some comments:
Slide 4: Icut_max/Icut_min
is 0.4/0.3-1=14.28% and not 7% as stated.
Slide 5: I like the simplicity
of how PD is specified in 802.3af then how it presented in slide 5: We
should allow utilizing the full 29.5W as permited by the average current
of 0.72A. We can do it easily by keeping the same concept and margins as
in 802.3af. Having 14.28% margin between Icut_max to Icut_min allows it.
It is difficult to understand
slide 5. I disagree with the 1st bullet. We should allow implementations
that uses dc current with ac ripple within the range specified between
Icut_max to Icut_min limited to 50msec max and 5% duty as in 802.3af.
Slide 6: The point of having
the current limit at the PD was to solve inrush current due to dv/dt in
PSE and dealing with long TLIM_MIN.
This slide suggests that PD with less then Cpd_max don’t
have to implement current limit. This was exactly the case in 802.3af so
what is the purpose of having all this PD current limit discussion? If
Cpd is 179.9UF<180U then Tlim _min may be still 12.6msec and we are
back to square 1 = 3month ago..
The solution is what I thought
last meeting: PD will limit the current within 1msec to ICUT_MAX so we
will have to charge only 0.12uF for the rest of the 50msec max of TCUT.
See my presentation that explains the whole thing.
Slide 6: This slide is relevant
only if PD limits to Icut_min. which doesn’t support a solution to utilizing
max 29.5W. See my presentation for proposal to solve this issue.
In addition, please allocate
time to discuss my presentation that may help to solve some issues that
was supposed to be solved by moving the current limit to the PD and in
my opinion are still requires some discussion.
The rest looks fine.
Yair
From: Fred Schindler (frs) [mailto:frs@cisco.com]
Sent: Tuesday, June 26, 2007 3:58 AM
To: STDS-802-3-POEP@listserv.ieee.org; Parker, Tim (SC100:321); Andrew
Smith; Wael Diab; mike@akrossilicon.com; Hugh Barrass (hbarrass); david_lucia@sifos.com;
sajol@sbcglobal.net; Dove, Dan; keith@phihongusa.com; Dinh, Thuyen; Patoka,
Martin; Daniel Feldman; Yair Darshan; Anoop Vetteth (avetteth); Clay Stanford;
Matthew Landry; David_Law@3com.com; Krellner Jan-r35458; david@akrossilicon.com;
Riccardo RUSSO; Huynh, Thong; Youhao Xi; McCormack, Michael; Bill Delveaux
(bdelveau); Pavlick Rimboim; Chad Jones (cmjones); Sanita Gianluca; Shinkyo,
Kaku; Joseph Maggiolino; Taylor, Rick; Brian Buckmeier; Soe, Myat Myitzu;
Unterdorfer, Pascal; EVM(Elsa Madrigal); christian.beia@st.com
Cc: Fred Schindler (frs)
Subject: IEEE 802.3at Vport ad hoc meetings Tuesday June 26; materials
Please ensure that you review the
IEEE-SA PatCom slides [ http://standards.ieee.org/board/pat/pat-slideset.pdf
] prior to the start of the conference call. At the start of call I will
ask that everybody confirms that they have read this material - if anybody
hasn't we will pause the call until they confirm that they have done so.
Thanks,
Fred
______________________________________________________________________________
Frederick Schindler has invited
you to a Cisco Unified MeetingPlace Conference
Date/Time:
JUN 26, 2007 at 9:00AM America/Los_Angeles
Length:
60
Frequency:
3
Meeting ID:
131128329
Meeting Password:
CISCO INTRANET ATTENDEES Join the Web & Voice Conference* 1. Go to http://meetingplaceinternal.cisco.com/join.asp?131128329 2. Enter your CEC User ID &
Password then click OK - Accept any security warnings you
receive and wait for the Meeting Room to initialize
3. Click on CONNECT from the
Meeting Room to join the Voice Conference portion of the meeting
EXTERNAL ATTENDEES
- Outside the Cisco Intranet** Join the Web & Voice Conference* 1. Go to http://meetingplace.cisco.com/join.asp?131128329 2. Fill in the My Name is field
then click Attend Meeting - If you have a CEC User ID, click
on the Cisco icon
- Accept any security warnings you
receive and wait for the Meeting Room to initialize
3. Click on CONNECT from the
Meeting Room to join the Voice Conference portion of the meeting
*If
this is your first time attending a Web Conference, disable any pop-up
blockers and visit http://meetingplace.cisco.com/mpweb/scripts/browsertestupper.asp
to test your web browser for compatibility with the Web Conference.
**Not
all meetings are scheduled to allow external attendees into the Web Conference
portion of the meeting, if the URL does not work, please follow the Voice
only Conference instructions below to attend.
TO ATTEND A VOICE ONLY CONFERENCE 1. Dial into Cisco Unified MeetingPlace
(view the Access Numbers and link above)
2. Press 1 to attend the meeting
3. Follow the prompts to enter the
Meeting ID 131128329 and join the meeting
SUPPORT Information about this Conference:
Contact Frederick Schindler, 14085259859
Cisco IT Support Center: Attend
the Voice Conference and then press #0 on your phone keypad
GLOBAL ACCESS NUMBERS COUNTRYLOCATIONLOCAL
NUMBERTOLL
FREE-FREEFONE AMERICAS United States
East +1.919.392.3330
1.866.349.3520
West
+1.408.525.6800 1.866.432.9903
Argentina
Buenos Aires +54.11.4341.0101
Brazil
Brasilia +55.613.424.0220
Rio de Janeiro +55.21.2483.6302
Sao Paulo
+55.11.5508.6311
Canada
Calgary +1.403.514.2435
Edmonton
+1.780.441.3715
Halifax
+1.902.474.0214
Kanata
+1.613.254.0005
Markham
+1.905.470.4810
Montreal
+1.514.847.6875
Ottawa
+1.613.788.7250
Quebec
+1.418.634.5645
Regina
+1.306.566.6410
Toronto
+1.416.306.7230
Vancouver
+1.604.647.2350
Winnipeg
+1.204.336.6610
Chile
Santiago +56.2.431.4936
Colombia
Bogota +57.1.325.6065
Mexico
Mexico City +52.55.5267.1800
Peru
Lima
+51.1.215.5101
Puerto Rico
San Juan +1.787.620.1865
Venezuela
Caracas +58.212.902.0210
EMEA Austria
Vienna +43.12.4030.6022
Belgium
Diegem +32.2.704.5072
Bulgaria
Sofia +359.2.937.5938
Croatia
Zagreb +385.1.462.8908
Denmark
Aabyhoj +45.8.939.7131
Copenhagen
+45.3.958.5010
Finland
Espoo +358.204.70.6227
France
Paris +33.15.804.3116
Germany
Eschborn +49.619.6773.9002
Hallbergmoos +49.811.554.3016
Greece
Athens +30.210.638.1303
Hungary
Budapest +36.1.225.4621
Ireland
Dublin +353.1.819.2717
Israel
Netanya +972.9.892.7026
Italy
Rome
+39.06.5164.4006
Netherlands
Amsterdam +31.20.357.1487
Norway
Oslo
+47.23.27.3647
Poland
Warsaw +48.22.572.2615
Portugal
Lisbon +351.21.446.8756
Slovakia
Bratislava +421.2.5825.5309
South Africa
Johannesburg +27.11.267.1011
Pretoria
+27.12.844.7401
Spain
Barcelona +34.93.393.4037
Madrid
+34.91.201.2149
Sweden
Gothenburg +46.31.63.4409
Stockholm
+46.8.685.9035
Switzerland
Glattzentrum +41.44.878.7335
Turkey
Istanbul +90.212.335.0208
United Arab Emirates (UAE)
Dubai +971.4.390.7840
United Kingdom
Bedfont Lakes +44.20.8824.0117
Edinburgh
+44.131.561.3643
London City +44.20.7496.3743
ASIA PAC Australia
Canberra +61.2.6216.0643
86.16.0643
Melbourne
+61.3.9659.4173
North Sydney +61.2.8446.5260
China
Beijing +86.10.8515.5666
HongKong
HongKong +852.3414.1802
India
Bangalore +91.80.4103.3979
Mumbai IL & FS +91.22.4043.4030
New Delhi
+91.11.4261.1088
Indonesia
Jakarta +62.21.7854.7476
Japan
Tokyo Akasaka +81.3.5763.9394
South Korea
Seoul Asem +82.2.3429.8102
Malaysia
Kuala Lumpur +60.3.7723.8620
Penang
+60.4.631.5125
New Zealand
Auckland +64.9.355.1968
Wellington
+64.4.496.5554
Phillipines
Makati (Manila) +63.2.750.5886
Singapore
Singapore Capital +65.6317.7088
Taiwan
Taipei +886.2.8758.7088
Thailand
Bangkok +66.2.263.7008
Vietnam
Hanoi +84.4.974.6250
Ho Chi Minh City +84.8.823.3418
(Saigon)
Fred Schindler
Technical Leader
CISCO Systems
170 West Tasman Drive
M/S SJ-19-3
San Jose, CA 95134-1706
Tel. (408) 525-9859