Linear Technology Corp.'s LTC4274 single-channel Power over Ethernet (PoE) controller is designed for power sourcing equipment (PSE) required to provide IEEE 802.3at (25.5W) or proprietary higher power levels. Next-generation PoE applications call for more power to support demanding features, while increasing power efficiency in an effort to be more "green" and reduce costs. The LTC4274 provides up to 100W over four-pair Ethernet cabling and is fully compliant with the new IEEE 802.3at PoE+ standard and backward compatible with the prior IEEE 802.3af PoE standard. To help conserve power, the LTC4274 delivers the lowest-in-industry heat dissipation by using low RDS(ON) MOSFETs and 0.25Ω sense resistors, eliminating the need for expensive heat sinks and providing a more robust PSE solution.
The LTC4274 is suitable for a wide variety of PSE applications, including next-generation single-port switches, cameras and electronic message boards. The extremely low power dissipation of the LTC4274 makes thermal design significantly easier than designing with PSEs that integrate more fragile, normally higher RDS(ON), MOSFETs. IEEE 802.3at powered devices (PDs) can request up to 25.5W of power, responding to 2-event classification from the LTC4274 and confirming that the PD is indeed a high power device. PD discovery is accomplished using a proprietary dual-mode, 4-point detection mechanism that ensures the best immunity from false detection. Advanced power management also includes prioritized fast shutdown, 14.5-bit voltage and current readback, 8-bit programmable current limits and 7-bit programmable overload current limits. A 1MHz I2C interface allows a host controller to digitally configure the IC or query port readings.
The LTC4274 is offered in commercial and industrial temperature grades, and is available in a RoHS-compliant 5x7mm QFN-38 package.
Linear Technology LTC4274 Single IEEE 802.3at PoE Controller
Linear Technology
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