Power over Ethernet (PoE) technology uses data network cables to transmit electrical power to devices. This allows a single cable to provide both data connection and power to devices like Wireless Access Points (WAPs), human-machine interfaces (HMI), and a wide range of other IP-enabled devices. The principal advantage of PoE is that it makes power cables unnecessary and saves customers the cost of cabling for both data networks and electrical power.
Benefits of PoE
Power and Data over a Single Ethernet Cable
PoE Standards
The supply of power via a Cat-5 cable is defined in the IEEE 802.3af Power over Ethernet standard. The PoE standards used to be limited to a few watts, but newer PoE technologies enable even higher power. For example, PoE + allows power up to 25 W per port and PoE ++ (a four-pair Power over Ethernet system) ranges from 70 W to 100 W by using all of the wires of the existing cable. In parallel to this PoE standard, Analog Devices has defined the proprietary standard LTPoE ++ ™, which defines the specifications up to 90 W powered device (PD) power (see table below).
Featured Products of PoE Standards
| PoE Standard | PoE Type | PD Power (W) | Usable Power (W) |
|---|---|---|---|
| PoE (IEEE 802.3af) | Type 1 | 13 | 11.25 |
| PoE+ (IEEE 802.3at) | Type 2 | 25 | 22 |
| ADI’s LTPoE++ | LTPoE++ | 38.7 | 32.9 |
| LTPoE++ | 52.7 | 44.8 | |
| LTPoE++ | 70 | 60.8 | |
| LTPoE++ | 90 | 76.8 |
Power-over-Ethernet (PoE) Interface Controllers
PoE Power Sourcing Equipment (PSE)
Featured Products of PoE Power Sourcing Equipment
| Part Number | No of Ports | PoE Standard | Product Description | PoE Type | Max Power (typ)/w |
|---|---|---|---|---|---|
| LTC4291-1 | 4 | IEEE 802.3af, IEEE 802.3at, IEEE 802.3bt | 4-Port IEEE 802.3bt PoE PSE Controller | 1, 2, 3, 4 | 71 |
| LTC4292 | 4 | IEEE 802.3af, IEEE 802.3at, IEEE 802.3bt | 4-Port PoE++ PSE Analog Controller | 1, 2, 3, 4 | 71 |
| LTC4266C | 4 | IEEE 802.3af | Quad PoE/PoE+/LTPoE++ PSE Controller | 1 | 13 |
| LTC4266 | 4 | IEEE 802.3af, IEEE 802.3at | Quad IEEE 802.3at Power Over Ethernet Controller | 2 | 25.5 |
PoE Powered Device (PD)
Analog Devices powered device (PD) controllers support multiple power levels of power over Ethernet: IEEE PoE (13W), IEEE PoE+ (25.5 W), IEEE PoE++ (71 W), and ADI LTPoE++ (up to 90 W) standard. PD controllers are ultimately responsible for providing the correct signature and classification to power sourcing equipment (PSE), so that PSEs source the right amount of power to PDs over the Ethernet cables. Some of the PD controllers integrate efficient dc-to-dc converters to simplify designs, while other PD controllers give designers the ability to choose their own dc-to-dc converters, which helps designers achieve unique cost-efficiency requirements.
Featured Products of PoE Powered Device
| Part Number | No of Ports | PoE Standard | Product Description | PoE Type |
|---|---|---|---|---|
| LT4293 | 1 | IEEE 802.3af, IEEE 802.3at, IEEE 802.3bt, LTPoE++ | LTPoE++/IEEE 802.3bt PD Interface Controller | 1, 2, 3, 4, LTPoE++ |
| LT4294 | 1 | IEEE 802.3af, IEEE 802.3at, IEEE 802.3bt | IEEE 802.3bt PD Interface Controller | 1, 2, 3, 4 |
| LT4295 | 1 | IEEE 802.3af, IEEE 802.3at, IEEE 802.3bt | IEEE 802.3bt PD Interface with Forward/Flyback Controller | 1, 2, 3, 4 |