[802.3af] Clarification- to the propose text
Hi
here is a clarification to the proposed text:
I propose we tell designers to test their PSE and their PD both
to a 'Hot' PSE - (opposite And same polarity) and be
done with this.
so here is the text:
"The PSE must tolerate the application of a voltage of the
same and of opposite polarity (up to 57v)
From another PSE*
without incurring any damage when such potentials are applied for an
indefinite amount of time."
* cause that PSE would be current limited to a max of 450ma and we assume
is to be shut off.
here we may choose to use a non PSE test when PICS is
written....
so the 'other' PSE may be a power supply with a limited
current of 450ma...
reasons:
some vendors (chips and system) already have put together hardware
with opposite polarity to what we all agree to, and feel like we do not
have
the right thing going here.
also for such a scenario to take place the following has to
happen:
1- Both PSE's must fault (not discover before powering) or both be '
HOT '.
we worked hard to insure this does not happen --in af.
2- We have a parallel diode that we specd (paid for) at the PSE end that
takes care
of a hot-plug the current can return to the originating PSE.
At the same time the diode helps a PSE discriminate by polluting anything
in the other PSE
that resembles a signature insuring no false discovery of another PSE....
No Hope here this
better be reality or we are in bad shape.
3- Even with all PSEs following a single polarity a cross over cable
would take us back
to the same problem again?!- if the PSEs are Hot - what am i
missing.
That was my 2c for today,
roger
Hi
I propose we tell designers to test their PSE and their PD both
to the 'Hot' - Opposite polarity and be done with this.
so here is the text:
The PSE must tolerate the application of a voltage of equal and opposite
polarity to its
own without incurring any damage when such potentials are applied for an
indefinite amount of time.
reason:
some vendors (chips and system) already have put together hardware
with opposite polarity to what we all agree to, and feel like we do not
have
the right thing going here.
also for such a scenario to take place the following has to
happen:
1- Both PSE's must fault (not discover before powering) or both be '
HOT '.
we worked hard to insure this does not happen --in af.
2- We have a parallel diode that we specd (paid for) at the PSE end that
takes care
of a hot-plug the current can return to the originating PSE.
At the same time the diode helps a PSE discriminate by polluting anything
in the other PSE
that resembles a signature insuring no false discovery of another PSE....
No Hope here this
better be reality or we are in bad shape.
3- Even with all PSEs following a single polarity a cross over cable
would take us back
to the same problem again?!- if the PSEs are Hot - what am i
missing.
That was my 2c for today,
roger