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[8023-POEP] IEEE 802.3at Vport ad hoc Wednesday; May 2; 9: Update on ILIM



Hello,

 

An updated ILIM slide is attached.  The calculations performed assume that a PD can draw ICUT for TCUT and that TCUT is longer than or equal to TLIM.  Therefore, a PD could legally draw ICUT constantly even if the PD voltage is increased.  If we do not want to allow this we need to put the appropriate language in the specification.

 

The PSE can only source ILIM_MIN when enough voltage difference exists between the PSE and the PD.  When a smaller difference exists, less than ILIM_MIN is sourced by the PSE and the PSE is no longer monitoring TLIM.  The PD voltage ramps to it final value exponentially from this point forward.

 

The values obtained match IEEE 802.3 needs and provide a shorter TLIM for IEEE 802.3at (because of the higher ILIM and the smaller voltage change).

 

Please provide comments before the next meeting on Wed. May 9.  Thanks for helping this specification move forward,

 

Fred Schindler

Technical Leader

CISCO Systems

170 West Tasman Drive

M/S SJ-19-3

San Jose, CA 95134-1706

Tel. (408) 525-9859

 

PS I would also like to thank Anoop Vetteth for his support on this effort.

IEEE 802 3at Task Force Vport I limits v2.pdf