RE: detecting a PD disconnection event

["Rick Brooks" <ribrooks@xxxxxxxxxxxxxxxxxx>]

Title: RE: detecting a PD disconnection event

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
>
>