Re: [8023-POEP] classification section intro text

["Darshan, Yair" <YDarshan@xxxxxxxxxxxxx>]

Hi Dan,

 

If the PSE supply current i.e. it is a current source and the PD is implemented as a current source too (The PD is actually implemented as a current source otherwise it is impossible to meet the tight current differences between classification ranges) then the voltage across the port is not defined. The voltage can be any number while the spec. requires 15.5V to 20.5V during classification. This requirement can be guaranteed ONLY is the PSE is a voltage source within the above range and the PD is a current source or "impedance" with very tight tolerance.

 

In short:

1. The PSE during classification can't be current source. It is a voltage source with defined accuracy.
2. The PD in order to meet the spec. current tolerances is implemented as current source.
3. You may use the word "impedance" due to the fact that if the PSE generate voltage and the result is current than the PD exhibits impedance at a value of Vclass/Iclass.

 

Yair

 

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From: owner-stds-802-3-poep@IEEE.ORG [mailto:owner-stds-802-3-poep@IEEE.ORG] On Behalf Of Dove, Dan
Sent: Friday, October 19, 2007 7:47 PM
To: STDS-802-3-POEP@LISTSERV.IEEE.ORG
Subject: Re: [8023-POEP] classification section intro text

 

Yair,

 

In case Geoff is not available, I can answer that; You may assert either a current or a voltage and measure the resultant voltage or current respectively.

 

Thus, Geoff's language is correct, although a minor typo is corrected below;

 

Hardware Physical Layer (HPL) classification occurs before power-on when the PSE asserts a specified signal onto the PI and the PD responds with an impedance representing one of a limited number of power classifications.

 

Regards,

Dan

 

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From: owner-stds-802-3-poep@IEEE.ORG [mailto:owner-stds-802-3-poep@IEEE.ORG] On Behalf Of Darshan, Yair
Sent: Friday, October 19, 2007 10:22 AM
To: STDS-802-3-POEP@LISTSERV.IEEE.ORG
Subject: Re: [8023-POEP] classification section intro text

Goeff ,

 

The spec. specify current range for each class. Why you prefer impedance?

 

Yair

 

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From: owner-stds-802-3-poep@IEEE.ORG [mailto:owner-stds-802-3-poep@IEEE.ORG] On Behalf Of Geoff Thompson
Sent: Thursday, October 18, 2007 8:56 PM
To: STDS-802-3-POEP@LISTSERV.IEEE.ORG
Subject: Re: [8023-POEP] classification section intro text

 

Chad-

Please change one sentence to be more precise:

From

Hardware Physical Layer (HPL) classification occurs before power-on when the PSE asserts a voltage onto the PI and the PD responds with a current representing a limited number of power classifications.

To

Hardware Physical Layer (HPL) classification occurs before power-on when the PSE asserts a specificed signal onto the PI and the PD responds with an impedance representing one of a limited number of power classifications.

Thanks

        Geoff


At 10:24 AM 10/18/2007 , Chad Jones (cmjones) wrote:

The text we are discussing in the AdHoc right now...
 

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