Power over Ethernet (PoE) Standards Overview

Introduction

Power over Ethernet (PoE) is a technology that allows Ethernet cables to carry electrical power, enabling devices such as IP cameras, wireless access points, and VoIP phones to receive power and data through a single cable. This simplifies installation, reduces wiring costs, and enhances flexibility in device placement. The IEEE^® 802.3af, 802.3at, and 802.3bt standards define the specifications for PoE, each offering different power levels to accommodate a range of devices. These standards ensure interoperability and reliability in delivering power over Ethernet, enabling a wide range of networked devices to operate efficiently and effectively. This lesson will cover details of these IEEE standards as well as some de-facto 4-pair standards.

IEEE® 802.3af-2003

This standard defines support for optionally powering a 10BASE-T, 100BASE-TX or 1000BASE-T DTE device via the Power Interface (PI) using physical layers defined in Clauses 14, 25, and 40. Power Sourcing Equipment (PSE) is located at an end point or midspan, separate from and between the Media Dependent Interfaces (MDIs) and provides power to the Powered Device (PD) over the link section. The PSE detection protocol distinguishes a compatible PD from non-compatible devices and precludes the application of power and possible damage to non-compatible devices. The PSE monitors the Maintain Power Signature (MPS) and removes power when it is no longer requested or required. Optional management function requirements are specified.

IEEE 802.3at-2009

This amendment includes changes to IEEE Standard 802.3-2008 to augment the capabilities of IEEE Standard 802.3 with higher power levels and improved power management information.

IEEE 802.3bt

The maximum PD power available was increased by this amendment to IEEE Standard 802.3-2018 by utilizing all four pairs in the specified structured wiring plant. This represents a substantial change to the capabilities of Ethernet with standardized power. The power classification information exchanged during negotiation is extended to allow meaningful power management capability. These enhancements provide higher power and more efficient standardized PoE delivery systems.

Power over HDBaseT™ (POH)

The initial specification of the standard, HDBaseT™ 1.0’s 5Play feature set offers long-range extension of Ultra-High Definition (UHD) audio, video, 100 Mbps Ethernet, control, and 100 watts power over a single category cable.  Although Spec 1.0 requires a minimum compatible cable type of Cat5e, Cat6 is recommended with signal distance support varying based on cable type, 1080p video up to 100m/328 ft. over Cat5e and higher, 4K video up to 70m/230 ft. over Cat5e and 100m/328ft. for Cat6a.

Released in 2013, HDBaseT 2.0 built on the breakthrough success of its predecessor by increasing distance capabilities of UHD 4K video at 30 Hz 4:4:4 or 4K video at 60 Hz 4:2:0 to 100m/328ft over Cat6 or 90m/295ft. over Cat5e.  USB 2.0 extension support was added to 5Play as part of the rebooted version, resulting in a more robust and interactive feature set.  Spec 2.0 also supports optical fiber for longer distances.

Making its debut in 2019, HDBaseT 3.0 is the most advanced and feature-rich generation of HDBaseT yet. It doubles its uncompressed data rate. HDBaseT 3.0 is the only technology to allow for the extension of fully uncompressed 4K video at 60 Hz 4:4:4 up to 100m/328ft. Additionally, its Ethernet capabilities were expanded from 100 Mbps to a full-duplex Gigabit. HDBaseT 3.0 recommends Category 6a U/FTP to recognize its full capabilities and potential.​

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Cisco® UPOE^®

In 2011, Cisco^® came up with an innovative approach to provide up to 60 watts with Cisco UPOE^® (Universal Power over Ethernet) over standard Category 5e or above cables. Cisco introduced its 90-watt-capable line card on the Cisco Catalyst^™ 9400 Series Switches and a 90-watt-capable switch in the Cisco Catalyst 9300 Series that are in complete compliance with the IEEE 802.3bt standard and supports Cisco UPOE.

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LTPoE++™

A new proprietary standard, LTPoE++™, extends the PoE and PoE+ specifications to 90W of PD delivered power. LTPoE++ also reduces engineering complexity in PSEs and PDs when compared to other power-expansion solutions. The capabilities of this standard expand the field of Ethernet-powered applications by several orders of magnitude, enabling entirely new classes of PDs, such as power-hungry picocells, base stations or heaters for pan-tilt-zoom cameras.

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Power Classes

PSE class is the maximum amount of power a port can deliver. a PD class is the maximum amount of power that the PD is designed to receive. Both PSEs and PDs are designed to be a particular class to meet their power capabilities and requirements. 802.3 bt standardized eight power classes. Classes 1, 2 and 3 (Type 1), are related to af power, Class 4 (Type 2) is related to at power and Classes 5 to 8 (Type 3 and Type 4), were added for more power. The power difference between the PSE and the PD is due to the expected power loss over the Ethernet cable.

“Type” refers to PSE or PD with common characteristics. IEEE currently standardizes four types:

The characteristics of the IEEE 802.3bt standard are divided into four types that support various classes. These classes have specific limitations of PSE and the PD power levels, PSE voltages and polarity. The new BT standard provides more power with higher data rates for applications such as Wi-Fi^® 6, smart LEDs and 5G small cells. It can provide up to 90 watts with data rates up to 10 gigabit per second to 100 meters of Ethernet cabling and is backward compatible with older standards and even to legacy devices.

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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 Aux Power in PoE
• Power over Ethernet (PoE) Solutions
• Power over Ethernet (PoE) Terminology

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