Re: [802.3af] voltage offset proposal (was 1-point detection, monotonicity)
Hi John
I think the 10.1v Max conflicts with a 500ua max out of the PSE
during detection for 500ua* max Rsig=26.5k (if i got this right)
that puts is at 13.25v max. do you know where the 500ua spec
came from?
also are we happy with the 2.8v being one VBE (diode drop away)
say at cold we allow 0.8v per diode that is 1.6v is this too tight?
thank you for taking the time to do this - there is no shortage of
confusion on the numbers...
regards
roger
>I have a proposal for the signature voltage offset requirement
>as seen by the PSE. However, before I generate an official
>comment to the editor, I am sending it to the reflector
>for comment. I believe the proposal below is in
>the spirit of our agreements, and it also eliminates
>the one-point detection "loophole" in our former discussion.
>
>The Proposal (in two parts):
>Part 1: Change the valid detection signature maximum
>voltage offset that the PSE might see to 2.8 volts,
>instead of 1.5 volts (see p.8, l.11).
>Part 2: Change the valid detection signature
>voltage range for the PD V-I characteristic
>to 2.7 - 10.1 volts, instead of 2.8 - 10 (see p.16, l.22).
>
>Rationale for Part 1: the 2.8 volt offset:
>Several meetings ago we agreed that the detection
>test voltage would be 2.8 to 10 volts.
>The 2.8 number was selected to allow for
>voltage offsets.
>
>Where did the 1.5 number come from?
>I think this is what happened.
>The PSE Detection Source Material gave its "must pass"
>requirements in the form of circuits that could include
>the "typical" two diodes. D1.2 put this into words.
>
>Rationale for Part 2: the 2.7 - 10.1 PD voltage range:
>This leaves a 100mV band for qualification testing,
>and ensures that a slightly-out-of-spec PSE
>will still detect a slightly-out-of-spec PD.
>(Thanks, Dave D.)
>
>John Jetzt
>