Two PSE Controllers Deliver 80 W For Class 5 PoE Power Injector

by Brian Rosario and Phill Leyva, Maxim Integrated, San Jose, Calif., How2Power Today, Jul 15 2015

Focus:
Many power over Ethernet (PoE) applications require 25.5 W or greater and Class 5 operation over a single port. This article explains how to use two power-sourcing-equipment (PSE) controllers with integrated power switches to obtain between 25.5 W and 80 W for a single-port PoE power application. This approach offers a cost-saving alternative to designs employing PSE controller ICs in combination with discrete power MOSFETs. It also provides higher power over a single port rather than resorting to a quad-port design. The article begins by discussing the wiring configuration required to transmit up to 80 W using Cat 5e cabling and the associated transformer/connector needs. Basics of the PSE, which will use either the MAX5971A or MAX5971B controller, and PD configurations are then given before describing in further detail the configuration of two MAX5971A PSE evaluation kits for full-power, single-port Class 5 operation. Test results for this PoE single-port power injector are provided in a separate spreadsheet.

What you’ll learn:

• How to design a single-port power-over-Ethernet power injector capable of delivering 80 W

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