RF802.3af PoE vs 802.3at PoE+: Key Differences
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PoE (Power Over Ethernet) allows Ethernet cables to supply power to network devices using the existing data connection. IEEE 802.3af and IEEE 802.3at are standards defining PoE’s functions and capabilities, enabling network devices to receive both data and electrical power over Ethernet cables.
PoE-capable devices can be Power Sourcing Equipment (PSE), Powered Devices (PD), or both. The device transmitting power is called the PSE, while the device receiving power is the PD.
Examples of PSEs include network switches or PoE injectors designed for use with non-PoE switches. PD examples are VoIP phones, wireless access points (APs), and IP cameras.
The IEEE standard 802.3at PoE+ is an update to IEEE 802.3af PoE. The main difference is that PoE+ PSEs can deliver approximately twice as much power over a single Ethernet cable. PoE+ PSEs can supply power to both PoE and PoE+ PDs, but PoE PSEs can only supply power to PoE PDs.
IEEE 802.3af PoE Type 1
Here are the features of the 802.3af PoE Type 1 adapter:
- Voltage range for PSE: 44 to 57 Volts; for PD: 37 to 57 Volts
- This standard provides DC power up to 15.4W; the actual power available to the device is about 12.95W after subtracting power dissipation in the Ethernet cable.
- Maximum current: 350mA
- Cable resistance: 20 Ohm (Max.) for Cat.3
- Maximum Cable Length: 100 meters (about 328 feet)
IEEE 802.3at PoE+ Type 2
The following are the features of the 802.3at PoE+ Type 2 adapter:
- Voltage range for PSE: 50 to 57 Volts; for PD: 42.5 to 57 Volts.
- Referred to as PoE+, it delivers DC power of about 25.5W.
- This standard can deliver 51W of power using a single cable, utilizing all four pairs in a Cat.5 cable.
- Maximum current: 600mA
- Cable resistance: 12.5 Ohm (Max.) for Cat.5
- Maximum Cable Length: 100 meters (about 328 feet).
Difference between 802.3af and 802.3at
Both require a minimum cable type of Cat.5e with 2-pair twisted cables.
Let’s compare 802.3af vs. 802.3at with respect to various parameters such as maximum power, voltage, cabling, and power management.
| Parameters | 802.3af PoE | 802.3at PoE+ |
|---|---|---|
| PoE type designation | Type-1 | Type-2 |
| Cabling | Cat 3, Cat 5 (or better) | Cat 5 (or better) |
| Maximum power per PSE port | 15.4 W | 30 W |
| Port voltage range | 44 to 57 V | 50 to 57 V |
| Maximum power to PD | 12.95 W | 25.5 W |
| Voltage range to PD | 37 to 57 V | 42.5 to 57 V |
| Power management | Class 0, 1, 2, 3 | Class 4 |
| Power pins | Uses all four pairs of wires (Pins 1, 2, 3, 6) | Uses all four pairs of wires (Pins 1, 2, 3, 6, 4, 5, 7, 8) |
| Use cases | IP phones, small cameras, and Wi-Fi access points | Larger cameras, some laptops, and more power-hungry access points |
Conclusion
These differences highlight the increased power delivery capabilities and broader device compatibility of IEEE 802.3at (PoE+) compared to IEEE 802.3af (PoE). PoE+ is better suited for devices requiring more power, making it a preferred choice in enterprise and industrial environments where higher-powered networked devices are commonly deployed.
