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Linear Tech intros PoE controller for power-hungry PD applications

Posted: 10 Apr 2007 ?? ?Print Version ?Bookmark and Share

Keywords:PoE interface controller? power-over-Ethernet controller? power-hungry applications?

Linear Technology Corp. has introduced a PoE interface controller for high-power Powered Device (PD) applications. The LTC4264 allows users to develop power-hungry applications beyond the IEEE 802.3af-mandated 12.95W limit, while still maintaining backward compatibility.

PoE+ support
The device can deliver up to 35W for 2-pair systems and as much as 70W for 4-pair systems. To control turn-on surge current in the system, the LTC4264 incorporates a precision dual current limiting circuit with an onboard power MOSFET and sense resistor to provide a complete inrush control circuit without additional external components. The device is compatible with the most current decisions on the PoE+ ( committee.

The precision dual level current limit enables legacy Power Sourcing Equipment (PSE) with limited current sourcing capability to power up the device while also allowing the device to draw full power from custom PSEs that exceed the limit of the existing standard. The LTC4264 is capable of handling 750mA with the lowest on-resistance (0.55 ohm typ, 0.8 ohm max) Hot Swap MOSFET on the market. The ultralow FET on-resistance minimizes power wasted by device heating and improves overall efficiency. Additionally, the user has the option to disable the normal operating current limit and to increase the maximum current limit to approximately 1.4A.

The LTC4264 features both active-high and active-low power good signaling for simplified interface to any DC/DC converter. The part includes an onboard 25-kiloohm signature resistor, precision undervoltage lockout and thermal overload protection. The signature resistor can be disabled so the device is not recognized or powered by the PSE in order to provide a seamless interface for an external wall adapter or other auxiliary power options.

802.3at support
The LTC4264 has the flexibility to support applications that meet the emerging IEEE 802.3at standard, as well as proprietary high-power applications. Specified over the full commercial and industrial temperature range, the device is offered in a thermally enhanced 12-pin 4-by-3mm DFN package for superior high-current performance. Pricing begins at $1.80 each for 1,000-piece quantities.

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