Electronic Design

Quad PSE Controller Meets IEEE 802.3at PoE+ Specs

The LTC4266 four-port Power over Ethernet (PoE) controller from Linear Technology targets power-sourcing equipment (PSE) that’s required to provide IEEE 802.3at (25.5 W) or proprietary higher power levels. It provides up to 100 W over four-pair Ethernet cabling. Also, it fully complies with the new IEEE 802.3at PoE+ standard and is backward compatible with the prior IEEE 802.3af PoE standard. Its low-RDS(ON) MOSFETs and 0.25-Ω sense resistors deliver the industry’s lowest heat dissipation, according to the company, and eliminate the need for expensive heatsinks for a more robust PSE solution.

The controller suits next-generation switches, routers, hubs, midspans, and other PSE applications. Its low power dissipation makes thermal design significantly easier than designs that integrate MOSFETs that are more fragile with normally higher RDS(ON), Linear says. Up to four independent PSE channels are available. IEEE 802.3at powered devices (PDs) can request up to 25.5 W by responding to two-event classification from the LTC4266, confirming that the PD is indeed a high-power device. PD discovery is accomplished using a proprietary dual-mode, four-point detection mechanism that ensures the best immunity from false PD detection, according to the company.

The LTC4266’s advanced power management also includes prioritized fast shutdown, 14.5-bit per-port voltage and current readback, 8-bit programmable current limits, and 7-bit programmable overload current limits. A 1-MHz I2C interface allows a host controller to digitally configure the IC or query port readings. Offered in commercial and industrial temperature grades, it’s available in 5- by 7-mm QFN-38 and SSOP-36 packages that comply with the European Union’s Restrictions on Hazardous Substances (RoHS). Pricing starts at $6.95 each in 1000-piece quantities.

Linear Technology Corp.

www.linear.com

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