Issue link: https://resources.mouser.com/i/1442796
Design Example Provides 6kV Protection Ethernet-based applications have moved outside. As IP cameras, wireless access points, and small cells have become more popular, the incidence of damage due to nearby lightning strikes has become more common in external Ethernet ports. Standards Compliance for External Ethernet Ports A variety of standards are in place that recommend the voltages and currents needed to test products for their ability to withstand surges due to lightning strikes. The most important standards are listed in the table below: The International Telecommunications Union (ITU) standard ITU-T is generally considered to be currently the most severe because, compared to the other standards, it uses smaller resistors to couple test surges into the ports being tested. Of the ITU-T standards, K.21 requires the most extreme surges. Using the smaller coupling resistors and larger surge voltages called out in ITU-T K.21, the product is exposed to, and must survive, larger surge energies compared to the other standards. Compliance with this standard will result in a more robust product able to handle more harsh environmental conditions. ITU-T K.21 has recently increased its enhanced pass criterion to 6kV. This change means that Ethernet components are exposed to much higher current and voltage stresses and require a new circuit design to ensure survivability. A GbE/PoE Port Designed to Survive ITU-T K.21 6kV Surges A design example is shown below that passes the new 6kV requirements. This design was put through the full list of pertinent K.21 tests (test details are found in the K.21 reference at the bottom of this article). Test 2.1.8 generated the largest surge voltages in the circuit and represents the worst-case test condition. If a product passes test 2.1.8, then it is expected to pass all the other K.21 tests as well. The surge is applied through a K.21 specified network to the pins of the RJ45 connector on the right side of the schematic. | 24 | Effective External Ethernet Port Protection By Paul Smith, Bourns, Inc. Document Notes GR-1089-CORE Issue 7, December 2017 IEC 61000-4-5 Edition 3.0 IEEE 802.3 2018, but currently being updated to include bt ITU-T K.20 7/2017, for central offices ITU-T K.21 7/2017, for customer premises ITU-T K.45 7/2017, for access and trunk networks