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Re: detecting a PD disconnection event


My preference is 1a.

Have the PSE disconnect if the AVERAGE value of load current is less than
10mA for a sample period of some time (say 100mSec)

This averaging produces a robust detection method from the standpoint of
system noise.



Barry Male                            
Senior Principal IC Designer          Internet: barry_male@xxxxxx
Power Management Products             NH Phone: 603.429.8705
Texas Instruments                     CT Phone: 860.844.8183 
7 Continental Blvd.                   NH FAX  : 603.424.3460
Merrimack, NH  03054-0399 USA         CT FAX  : 860.844.8806

On Fri, 27 Apr 2001, Rick Brooks wrote:

> Just to start up another discussion, I wanted to find out how many people
> would support
> the following concept for detecting when a PD receiving power becomes
> disconnected.
> the concept:
> $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$
> 1) The PSE is responsible for detecting when a PD receiving DTE power
> becomes disconnected.
> If that event occurs, the PSE must turn off the power within some time frame
> (100ms to 500ms ballpark?)
> 2) The PSE may use any of the following methods to detect this PD disconnect
> event.
> 	a) the DC load current drop below "X" ma (10ma?)
> 	b) the ethernet link has dropped out
> 	c) another proven method (pending discussion and feasibility proof)
> 		some suggestions:
> 		1) the AC probing circuit detects when the AC load changes
> (opens)
> 		2) the PD modulation heartbeat current ceases
> 		3) the PD response to a given PSE code is wrong or absent
> 		4) other ideas
> $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$
> Please voice your opinions on this concept.
> The motivation here is to lower the cost of delivering DTE power.
> thanks,
> - Rick