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RE: detecting a PD disconnection event




Hi Barry

I support Rick's statement here, and so long that we have more than one
way of predicting an unplug - live and let live.
roger


At 10:39 AM 4/27/01 -0700, Rick Brooks wrote: 

>
> Barry, 
> 1a) was all of our favorites until Geoff's recent email regarding a patent
> issue. 
>
> It may turn out that other methods are more cost effective when considered
> globally. 
> My proposal is that more than one method could be used, not just the one that
> we have been assuming. 
> My view is that we must at least consider alternative methods that do not use
> DC current sensing. 
>
> thanks, 
> - Rick 
>
> -----Original Message-----  From:   Barry Male
> [SMTP:male@xxxxxxxxxxxxxxxxxxxxxx]  Sent:   Friday, April 27, 2001 10:29 AM 
> To:     Brooks, Rick [SC5:321:EXCH]  Cc:     stds-802-3-pwrviamdi@xxxxxxxx 
> Subject:        Re: detecting a PD disconnection event 
>
> Rick, 
>
> 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. 
>
> Thanks 
>
> Barry 
>
> _________________________________________________________________  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  >  >