Electronic Design

Controller Anticipates PoE Plus

Power over Ethernet Plus (PoEP) is still a work in progress. At its March meeting, the IEEE 802.3at PoEP Task Force was still considering test methods simply for evaluating the current-carrying capacity of bundled data wires, and most discussions centered on powered-device classification.

Yet earlier this month, PowerDsine raised the stakes by introducing a highpower controller, the PD83000, for fourpair Ethernet-cable power delivery. Intended applications include video-screen phones, WiMax transmitters, pan-tilt-zoom security cameras, and thin clients.

The chip set can provide switch vendors with a minimum of 30.8 W and could potentially achieve 56 W. Deployed with PowerDsine's four-or 12-port chip (the PD64004A and PD64012G, respectively), it can provide a maximum of 48 high-power ports.

The basic IEEE 802.3af standard distributes current over two pairs in a CAT5 cable. These pairs can be either the data pairs or the "spare" pairs. Either way, basic PoE is limited to 15.4 W at the sourcing end.

Originally, the limitation wasn't seen as a significant barrier. That's because the intended applications primarily were non-video Voice over Internet Protocol (VoIP) phones, wireless local-area network (WLAN) access points, and stationary IP cameras. But once the 802.3af standard was in place, everybody suddenly wanted more power.

The PD83000 uses a synchronization algorithm for the power-sharing circuitry in powered devices that makes them less expensive to implement. It also combines data and status information from the data and spare pairs onto a single logical port for the switch/router vendor's ease of use.

The PD83000 costs $9.75 in quantities of 1000 units.


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