Power Electronics

PoE Offerings Address High-Power and Wireless Applications

At the Interop 2007 exhibition recently held in Las Vegas, several semiconductor vendors unveiled components and systems to address the demand for high-power PoE equipment. Originally developed to power IP telephones, PoE now encompasses applications requiring 30 W and even 60 W, such as powering Wi-Fi access points. This has resulted in the emergence of components and systems intended to support both existing and anticipated PoE standards.

An excellent example of these offerings are Broadcom’s first PoE products, which were announced at Interop. These two highly integrated 4-port power sourcing equipment (PSE) controllers target enterprise, small-to-medium-sized business and residential environments. The BCM59101 (IEEE802.3af-compliant) and the BCM59103 (pre-IEEE802.3at) controllers can result in 30% fewer components. For applications that require higher power, the BCM59103 can be dropped into the BCM59101 footprint to provide 37 W per port, expanding the applications for Ethernet switches to include high-power applications such as 802.11n wireless access points, video and security technologies.

Covering the downstream side, National Semiconductor’s PoE PD controller with adjustable output current, the LM5073 (introduced the same day, but at PCIM in Nuremberg, Germany, not Interop), can interface with any dc-dc converter topology. This device is also capable of exceeding standard IEEE 802.af specifications, supporting power levels greater than 30 W. The 100-V maximum voltage rating simplifies selection of the voltage suppressor that protects the PD from network transients. The LM5073 also provides the flexibility for the PD to accept power from unregulated auxiliary sources such as ac adapters and solar cells.

At the middleground of these two applications, Microsemi unveiled a one-port high-power Gigabit midspan, the PD-7001G. The latest member of its PowerDsine product portfolio, this unit maintains the existing IEEE 802.3af standard. In keeping with the previously mentioned devices, this unit also provides double the power capacity required to support the existing PoE standard, producing a minimum of 30 W at the port output at greater than 80% efficiency. The gigabit interface makes this unit suited for Gigabit video phones, WiMAX transmitters or 802.11n access points.

Also introduced were Phihong’s 60-W midspan and 52-W PoE Gigabit high-power splitter specifically designed to support high-power wireless access points. Designated the POE60U-560G, the midspan is designed to power wireless access point arrays and WiMAX access points that require up to 52 W of power. The 60-W midspan features diagnostic LEDs and the same safety and protection systems as with the IEEE 802.3af standard, including detection, disconnect and overload control. The device is also Gigabit-compatible. The midspan has been tested for compatibility and broadband data-handling capability by UNH IOL.

The POE60D splitter is a Gigabit-compatible device designed to be mounted adjacent to a powered device, performing the connect identification function as well as separating the power and data. Both the splitter and midspan are designed around the current specifications of the proposed IEEE802.3at standards, and are ideal for implementing PoE for driving multi-radio access point arrays in business and educational environments.

Finally, Akros Silicon announced the availability of its highly integrated AS1100 family of PD devices. The AS1100 family includes the AS1113 device for the IEEE 802.3af-2003 specification’s power levels and the AS1124 device for either 802.3af or 802.3at pre-standard power levels. The AS1113 for 13-W applications includes the current 802.3af PD standard. The AS1124 for 24-W applications encompasses the pre-802.3at standard with “two finger classification” and is backward compatible with the current 802.3af specification. These devices, built on standard HV CMOS technology, include system-level circuitry for lower EMI emissions and robust surge protection in addition to the PD controller functionality. A key requirement of POE systems is immunity to overvoltage and surge events. Integrating the diode bridge and protection circuitry significantly increases the reaction time of protection devices and PHY immunity to overvoltage stress events.

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