If you're close to entering the power-over-Ethernet market with a power interface device, don't miss the next test session at the University of New Hampshire's Interoperability Lab (Durham, N.H.) Aug. 4-8. The 802.3af standard defining how power should be delivered to portable and remote devices over Ethernet ports may well have been "ratified" (see June 30, page 26). But that doesn't have a thing to do with designing your product to meet a final, unambiguous document.
Ironically, new standards are usually just the start of something that gets a lot bigger. "Device compliance and compatibility are not the same thing," notes Jonathan Bearfield, product manager for Texas Instruments System Power, a member of the Power-over-Ethernet consortium. Issues accrue, Bearfield says, especially in systems such as power-over-Ethernet where one end of the link sets a minimum power provision and the other a maximum.
In this case, designers speak about power-sourcing equipment and the powered devices, probing a device for its "signature" impedance to define its power class, and so on. It sounds simple, but that's deceptive.
Indeed, the term "finalized" generally has little meaning with an IEEE spec; like a peace treaty, it's an ongoing process-always has been and always will be. The only difference with power-over-Ethernet product shakedowns is perhaps this technology's faster head start, according to Bearfield, given the UNH facility's previous experience as a compliance-testing facility for such projects as Gigabit Ethernet.
The basic premise, however, never changes, and that's to have the lab check out interoperability and parametric testing in a neutral, multivendor test environment before, not after, the product hits the market. That "keeps the peace," although there are always people who may not interpret the standard the same way or who want to stretch its limits. Doing so often results in adding a special device classification. One example is charging batteries from a portable source, never a central goal of power-over-Ethernet but one that's become associated with it. It's a fair bet that application will create issues that eventually require altering the spec.
The best solution is to get involved directly, taking nothing for granted. The August "plugfest" will be attended by some well-known companies including Nortel and PowerDsine, but it's basically open to anyone willing to make a commitment to the consortium's goals. Given the huge market most see coming, I'd say it's a good investment.
Vincent Biancomano covers power products for ProductWeek. Contact him at 103520.355@compuserve.com.
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