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PoE interface controller delivers precise regulation

Milpitas, Calif. — Linear Technology has introduced the LTC4268-1, a Power over Ethernet (PoE) interface controller with a synchronous, current mode, switching regulator for delivering precise regulation and high efficiency to powered devices (PDs). The LTC4268-1 provides up to 35 W for 2-pair systems and up to 70 W for 4-pair systems.

The LTC4268-1 device's high-performance switching regulator is optimized for isolated PoE applications. The PoE interface controller incorporates Linear Technology's NoOpto feedback topology to provide full IEEE 802.3 isolation without the need for optoisolator circuitry. A feedback amplifier senses the output voltage through the transformer winding during the flyback period and uses this voltage to tightly regulate the output. The transformer isolates the load from the input supply and provides feedback, improving output transient response and overall reliability, said Linear.

The LTC4268-1 offers programmable switching frequency from 50 kHz to 250 kHz. In low-noise system designs, the controller can be synchronized to an external oscillator. The controller is capable of handling 750 mA with the a low on-resistance (0.55 ohm typ) Hot Swap MOSFET. The ultra-low FET on-resistance minimizes device heating and improves overall efficiency, said Linear. For even higher output power, the normal current limit can be disabled, allowing implementation of proprietary, ultra-high-power designs.

In addition, the LTC4268-1 includes a PD controller front-end. By incorporating a precision dual current limit, the LTC4268-1 ensures interoperability with any Power Sourcing Equipment (PSE). Specified over the commercial and industrial temperature ranges, the LTC4268-1 is offered in a 32-pin, 7 x 4-mm thermally enhanced DFN package.

Pricing: Starts at $2.40 each in quantities of 1,000.

Product information: LTC-4268-1

Linear Technology Corp. , 1-408-432-1900, www.linear.com

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