Issue link: https://resources.mouser.com/i/1442796
Power over Ethernet (PoE) simplifies and reduces the cost of wired networks because it combines power and communications over a single CAT5 Ethernet cable. The technology gained traction when it was amended to the IEEE 802.3 Ethernet standard. That specified how standard cables could be configured to carry up to 15.4W and 44 to 57V DC alongside data. Later, a higher power version was added which allowed for 30W and 50 to 57V DC. Higher power (60 and 90W) versions of the specification were ratified in October 2018. But while transmitting both power and data on a single cable is convenient, the downside is every Powered Device (PD) is connected to a single network which exposes the devices to damage from a single electrical transient (overcurrent or overvoltage) event. To avoid damage to PDs connected to these PoE systems, designers must include circuit protection such as blocking, suppression and isolation. This article describes how to design-in this protection. Sources of electrical transients There are multiple sources of electrical transients and each has unique rise time, peak voltage and decay characteristics. Such transients have been categorized (by IEC transient immunity standards) as electrostatic discharge (ESD), fast voltage/current transients or voltage/current surges. (IEC 61000-2/4/5 defines the immunity test methods to determine if the equipment under test meets the electrical transient immunity standards.) Designing Electrical Transient Protection for Power over Ethernet By Steven Keeping for Mouser Electronics Power over Ethernet brings convenience to networks by combining communication and power in the same cable. The downside is that every device on the network is exposed to damage from a single electrical transient. To avoid damage to the sensitive electronic components that form part of these PoE systems, designers must include circuit protection such as blocking, suppression and isolation. | 4 |