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[802.3_4PPOE] Your proposal for Single-signature definition in

Hi David,

  1. I have reviewed your proposal and I see that the current injection method may not work if you are looking for invalid signature i.e. 25K.

The reason is that when you inject two current levels in mode A (I1, I2 and e.g. I1>I2) and find valid signature (25K) on that mode while the current on mode B is 0, and then you inject new current level I3 on mode B while you keep I2 in mode A, you will get valid slope of 25K (I am ignoring the offset voltage for now) which means it shows a valid signature (25k) while I supposed to get invalid signature (in terms of resistance and no other parameters that defines invalid signature).

  1. In general, any current you inject on mode B when mode A is conducting will just generate offset voltage across Rsig but will not change the slope of Rsig=25K. The reason for it is that detection is done always in differential way (two values of current or voltage) which cancel offsets.
  2. The best approach to define single-signature PD is to use the voltage concept. It will always work. Please remember that the way we define the PD is it single-signature or not should not imply and doesnt not imply how we implement connection check. Moreover, I am also suggesting adding a text that say it explicitly.


To summarize:


I prefer the following definition:

A single-signature PD shall present a valid detection signature, as defined in Table 145-21, on a given Mode when no voltage or current is applied on the other Mode, and shall present an invalid not present a valid detection signature on that Mode when any voltage between 10.1V and 57V at least one voltage between 3.7V and 57V is applied to the other Mode or any current greater than 124μA is applied to the other Mode. These requirements apply to both Mode A and Mode B.

This definition doesn’t imply on the way how connection check is implemented weather using voltage or injecting current.”



NOTE—A valid detection signature meets every requirement in Table 145-21 across all specified conditions. A failure under any allowed conditions of Table 145-21 is considered “not a valid signature while “invalid signature” is when the requirements of Table 145-22 are met. 









Darshan Yair

Chief R&D Engineer

Analog Mixed Signal Group

Microsemi Corporation


1 Hanagar St., P.O. Box 7220
Neve Ne'eman Industrial Zone
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Tel:  +972-9-775-5100, EXT 210.

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E-mail: <mailto:ydarshan@xxxxxxxxxxxxx>.