New PoE Controller Enables Multiple High Power Ports

May 3, 2006 11:12 AM
By Mark Valentine, Technical Editor

PowerDsine has released the PD83000, a new high-power PoE controller for next-generation Ethernet devices.  Combined with the 4- or 12-port PD64004A or PD64012G, up to 48 high power ports can be provided from a single system. While IEEE 802.3af requires that at least 15.4 W be available for the powered device, the new chipset provides a minimum of 30.8 W of power per port, which can potentially be increased to 56 W with voltage and current scaling.

"PoE has grown by leaps and bounds," stated Madhu Rayabhari, Vice President of Marketing for PowerDsine, "especially for such applications as wireless LAN access points and security cameras.  However, the power requirements for emerging PoE applications, such as video-equipped VoIP phones, WiMax transmitters and Pan/Tilt/Zoom cameras, are exceeding the capacity required by IEEE 802.3af.  This was the motivation behind the development of the PD83000 and related products, in which power is delivered through both the data and spare pairs of the Ethernet cable."

Even with the increased power capacity of the new chipset, it is possible to design systems without incurring a penalty in the thermal management at the system level, which is maintained within the limits of practical design. The power dissipation requirements of the chipset are a function of the power drawn by the Ethernet ports. The power manager components that supply power directly to the ports, such as the 64004A, are designed for improved thermal performance and aid in simplified thermal design of the system.

The PD83000 also supports sophisticated power management features beyond those called for by IEEE 802.3af, stated Rayabhari. For example, the system can develop and maintain a load profile of the powered device on each port. The power delivered by the ports can be controlled through software, and in instances where the load exceeds the total system power budget, ports can be turned off gracefully to maintain operation within the total budget, according to pre-assigned port priorities that the user can program into the system. In the future, control mechanisms can be adopted to enable a single powered device supplied from two Ethernet ports in parallel.  This would be a straightforward modification to existing control capabilities, and the single powered device would then simply be reported as two separate devices.

It then becomes conceivable that in the future, the power used by a single powered device could reach levels higher than 56 W, and the question of safety regulations for these systems will naturally arise as power levels increase.  There are standards that limit current within Ethernet cables for PoE, and the current levels used by the PD83000 are well within these limits.  However, as power and current levels increase, it is likely that the Telecommunications Industry Association (TIA), or a similar organization will establish additional regulations for PoE cabling.  While these developments are somewhat distant, the more exciting prospect of new high-power PoE applications enabled by the PD83000 is close at hand.

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