| Thread Links | Date Links | ||||
|---|---|---|---|---|---|
| Thread Prev | Thread Next | Thread Index | Date Prev | Date Next | Date Index |
|
Hi Joris, Few questions/
During 802.3af/at the 28uA came from the calculations shown in darshan_01_0518.pdf attached on page 18. It is based on a diode with minimum equivalent leakge resistor of 1Mohm. In real life, PDs that where using Schottky, pass the backfeed
test. If you look at the calculation, asymmetry of 10:1 between diodes where taken. Regards Yair From: Joris Lemahieu [mailto:Joris.Lemahieu@xxxxxxxxxx]
EXTERNAL EMAIL Hi all, I believe we are on the right track with the updates represented in the ‘yseboodt_01_0518_backfeed_baseline’. The only concern I still have is with a “3-Pair PSE” trying to detect a single-signature PD (just for a single port system). I have the impression the (schottky) diode reverse leakage has not always been taken into account properly: either just neglected or represented as being a resistor (without additional current source in parallel). See my presentation in attachment. My concern is that a PD with real (schottky) diode bridges might become non-compliant to the 3bt standard and that a “3-Pair PSE” would be allowed not being able to detect a PDs with real (schottky) diode bridges anymore, due to hard to meet leakage current requirements. As such I do not have any problem with that, but do we really want to go that far? Next to my presentation, I also attached a spice schematic file for those that would like make simulations. FYI, the name “3-Pair PSE” is short for
“a 4-pair capable PSE providing power in 2-pair mode, whereby two pairs are connected to the positive VPSE, and one pair is connected to
the negative VPSE“. Best Regards, Joris Lemahieu Application Engineer ON Semiconductor +32 55 33 29 49 To unsubscribe from the STDS-802-3-4PPOE list, click the following link:
https://listserv.ieee.org/cgi-bin/wa?SUBED1=STDS-802-3-4PPOE&A=1 To unsubscribe from the STDS-802-3-4PPOE list, click the following link: https://listserv.ieee.org/cgi-bin/wa?SUBED1=STDS-802-3-4PPOE&A=1 |
Attachment:
darshan_01_0518Rev005.pdf
Description: darshan_01_0518Rev005.pdf