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Low-cost IC drives PoE devices

Posted: 01 Dec 2006 ?? ?Print Version ?Bookmark and Share

Keywords:Freescale Semiconductor Inc.? PoE? Ethernet? Linear Technology Corp.? Texas Instruments Inc.?

Freescale Semiconductor Inc. is rolling out its first chip for end devices that draw their power from an Ethernet line. The MCZ34670 is geared to undercut compeTItors like Linear Technology Corp. and Texas Instruments Inc. (TI) by offering lower prices, owing to advanced process technology.

Freescale has been supplying 12-port chips with integrated MOSFETs to hub and router makers who want to deliver PoE for two or more years now. Cisco estimates that as much as 60 percent of its desktop Ethernet hubs and switches now support PoE, a figure that could rise to 95 percent by 2008, the Ethernet giant believes.

A class of so-called midspan devices has already emerged to add power signals to Ethernet lines emerging from existing hubs and switches. The simplified devices made by companies like Linksys and NetGear can cost as little as $100 for a four-port unit. As the network gear gains traction, Freescale sees a growing opportunity to deliver chips for end devices like VoIP phones, wireless access points and network security cameras that sip their power from a data line.

"We didn't put a lot of emphasis on this in the beginning, but we think the market is ripe for it now," said Andy Khayat, a marketing manager in Freescale's power-management and motor control group.

Market watcher Venture Development Corp. predicts that PoE devices will grow from an estimated 45 million shipped in 2005 to as many as 152 million in 2008. The biggest slice of that market is in VoIP phones, which could expand from 6 million to 21 million units over the same period.

The problem is that the IEEE 802.3af-2003 standard for PoE defines a pretty tight set of features, making it difficult to distinguish one device chip from another. "The chips are pretty much me-too products. Our chip is pretty much the same as the competitors', thanks to the standard," Khayat said.

"The bad thing is that we wind up having a lot of competition, but it's good for OEM customers," he added.

To stand out, Freescale makes its parts in 250nm BiCMOS technology, compared with many competitors' 350nm process. The process edge translates into a die that is about 30 percent smaller than that of its rivals, and that translates into a published price of $2.08 in 10,000-unit quantities. The chips are available in production quantities now.

Inside the handoff of PoE, one wire pair sends 15W and 48V from net-to-end device.

Engineers are already upgrading the standard to a so-called PoE Plus. They hope to push the 15W-, 48V-standard to 24-30W in a new IEEE group.

Cisco, Broadcom, Freescale, Linear, National Semiconductor and TI are all participating in the PoE Plus standards effort. A Freescale representative said that completing a draft standard could take until the end of 2007.

So far, two proposals have surfaced. One would push as far beyond today's 350mA transmission rates as possible, using the existing channels of one of Ethernet's four wire pairs, the data or so-called spare pair. That proposal peaks at about 24W, since transmitting a full 700mA on a single pair essentially fries the copper cables' dielectric insulation, rendering them useless. A contending proposal would send 350mA over both the data and spare wire pairs to hit 30W at 48V. Just how the debate will be sorted out remains unclear.

Still, all share the same goal. "Eventually you will be able to plug a notebook into the Ethernet network and not need a charger. That's the Nirvana," said Khayat.

- Rick Merritt
EE Times

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