Introduction to Power over Ethernet (PoE)

What is Power over Ethernet?

Power over Ethernet (PoE) is a technology that enables the delivery of electrical power along with data over standard Ethernet cables, such as CAT5e, CAT6, and CAT6a. This innovation simplifies the installation of networked devices by eliminating the need for separate power supplies and electrical wiring, making it an efficient and cost-effective solution for various applications.

There are three IEEE^® standards, 802.3 af, 802.3 at and 802.3 bt. The af standard supports up to 15 watts, at supports up to 30 watts and the new bt standard supports up to 90 watts. PoE is compatible with 10, 100 and 1000 megabit per second data rates and up to 10 gigabit per second for the bt standard. The maximum range is 100 meters.

PoE Applications

PoE can power a variety of devices. Any network device that consumes less than 90 watts is a candidate for PoE. It can be an internet switch, access point, wireless backhaul, 5G small cell, IP camera, IP phone, LED lighting, access control, information kiosk or a Point-of-Sale (POS) terminal.

Why do we want to use PoE? First, it reduces installation costs since a licensed electrician is not needed to run new AC lines. The PoE bus uses less than 60 volts, which makes PoE systems very safe. PoE is highly scalable; there is no need to power down the system to plug or unplug new devices. Also, remote power management is available to set schedules and control network power.

Here are some application examples that benefit from PoE:

• IP Cameras: PoE is widely used in surveillance systems to power IP cameras, allowing for easy installation in locations without nearby power sources. This is particularly useful for outdoor and remote monitoring.
• Wireless Access Points (WAPs): PoE powers wireless access points, enabling flexible placement to optimize Wi-Fi^® coverage without the need for electrical outlets.
• VoIP Phones: PoE simplifies the deployment of VoIP phones by providing both power and data through a single Ethernet cable, making it easier to set up and manage office communication systems.
• Network Switches: PoE-enabled switches can power other PoE devices, such as IP cameras and WAPs, streamlining network infrastructure and reducing clutter.
• Digital Signage: PoE supports digital signage installations in locations where running separate power lines would be challenging or costly, such as retail stores, airports, and public spaces.

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Advantages of PoE

PoE is an international standard that uses one RJ45 cable. Because it can deliver both power and data, PoE reduces installation costs by eliminating the need to install additional AC outlets and avoiding the need for a licensed electrician.

PoE is flexible, scalable and easy to deploy. It is plug and play; a PoE device can be added or removed from the network at any time without bringing the network down. Remote power management can control and power cycle PDs and support user-defined schedulers to turn on and off PoE powered devices. It can also prioritize power to PoE ports. Finally, PoE is a safe and secure wired connectivity. It uses less than 60 volts, which is Safety Extra Low Voltage (SELV), while constantly monitoring port behavior and status.

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PoE Components

The two main components in the PoE are the Power Sourcing Equipment (PSE) and Powered Device (PD).

A PSE determines whether the connected PD is valid, classifies the power capability of the PD, controls power, performs power optimization and allocation, monitors power consumption, disconnects in case of undercurrent, short or over-voltage and isolates switch circuitry.

A PD is responsible for polarity protection, providing a signature for detection and classification, controlling the powered application and converting high PoE voltage down to the voltage required by the application. It also provides in-rush current limiting upon initial power.

There are two types of PSE components, an Endspan, which is a PSE integrated inside an Ethernet switch and a midspan (or PoE injector), which is placed between a non-PoE Ethernet switch and a PD.

Here, a non-PoE switch is connected to a midspan. The midspan takes the data from the non-PoE switch and adds power into it.

Summary

Power over Ethernet is a versatile and efficient technology that streamlines the deployment of networked devices by combining power and data transmission over a single cable. Its benefits include simplified installation, cost savings and enhanced flexibility, making it an ideal solution for a wide range of applications from surveillance systems to wireless networking and beyond.

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Learn More

• Power over Ethernet (PoE), Power Delivery (PD) and DC-DC Design Considerations
• Designing a Type 1/2 802.3 or HDBaseT Type 3 Powered Device Front End Using PD702x0 and PD701x0 ICs
• Designing a Type 1/2 802.3 or HDBaseT Type 3 Powered Device Using PD702x1 and PD701x1 ICs
• Implementing Auxiliary Power in PoE
• Power over Ethernet (PoE) Solutions
• Power over Ethernet Terminology

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