What about Power over Ethernet in a hazardous environment?

Bitbanger's comment on an earlier post, "Top six reasons to consider Power-over-Ethernet for your office/factory/home application," was “Poe is nice, but what about hazardous environments?" Good question, and worth digging into. Itook it to Mike McCormack, Biz Dev manager for PoE products at TI, and he had this to say about PoE and hazardous environments:

"Hazardous environments are covered by a number of safety standards because the concern is about anything that could spark or ignite a fire. This is much more stringent than the typical safety UL or CSA rules which are centered on ensuring the devices themselves will not combust. While this is overly simple, the rule of thumb is that these "intrinsically safe" devices must be limited to less than 30VDC and 4W.

The IEEE standard for Power over Ethernet (IEEE Std 802.3-2005, Clause 33) requires, among an number of other things, a minimum output voltage of 44V at the Power Sourcing Equipment (PSE) and the Powered Devices (PDs) must operate from 36 to 57VDC.At the very least these voltages would not allow a standards compliant PoE system to operate in the hazardous environments the writer enumerates."

Mike says that TI has a PSE, the TPS23841, and PD, the TPS2376-H, which can operate as low as 24VDC nominally. So these parts can be used, with appropriate design practices, to create an "intrinsically safe" PoE system.TI's aim is to extend the benefits of PoE to the hazardous environment that Bitbanger asks about, as well as opening PoE to other severely safety conscious applications in medical or industrial markets. Keep in mind that these types of systems would not be compliant with the standard; however, it would provide the benefits of PoE to these applications.

Thanks, Mike!