Integrated Protection and Careful Layout Protect PoE Systems from EOS and ESD

Focus:

The IEEE-802.3af standard defines equipment for supplying power via an Ethernet cable. But as is usually the case when electrical devices are connected by cables, those devices are subject to interference from electrostatic discharge (ESD) and electrical over stresses (EOS). This article reviews the operating principles of Power over Ethernet (PoE) systems and describes the EOS and ESD standards that PoE systems must comply with. (Specifically, these are the surge immunity standard IEC61000-4-5 and the ESD immunity standard, IEC61000-4-2 standard level 4.) With this as background, the article presents a solution for PSE-side protection based on STMicroelectronics' PEP01-5841 quad Transil device, which reduces pc board-space requirements while improving protection of the PSE controller. The article also presents PCB layout techniques for suppressing the high di/dt of an ESD event.

What you’ll learn:

• How to implement ESD protection and surge immunity for PSE-side controllers in power over Ethernet systems
• How to understand requirements imposed by the IEC61000-4-5 surge immunity standard and the IEC61000-4-2 standard level 4 ESD immunity standard in power over Ethernet systems

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Author & Publication:

A. Bremond and C. Appere, STMicroelectronics, Tours, France, How2Power Today, Mar 30 2010

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