Power over Ethernet interface controller integrates a synchronous current-mode switching regulator for delivering precise regulation and high efficiency

Linear Technology has released 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 power-hungry powered devices (PDs). The LTC4268-1 provides up to 35W for two-pair systems and as much as 70W for four-pair systems.

As the momentum for PoE continues to grow, the LTC4268-1 bridges the gap to enable development of innovative high-power PoE devices in anticipation of the evolving PoE+ (IEEE802.3at) standard.

At the heart of the LTC4268-1 is a high-performance switching regulator optimised for isolated PoE applications.

The LTC4268-1 incorporates Linear Technology’s patented NoOpto feedback topology to provide full IEEE802.3 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.

The synchronous flyback convertor provides a low part count design with the advantage that additional outputs can be obtained by simply adding windings.

Synchronous rectification offers the benefit of higher output power, increased conversion efficiency and improved cross regulation in applications with multiple outputs.

The LTC4268-1 offers the flexibility of programmable switching frequency from 50 to 250kHz for optimised power supply design.

In low-noise system designs, the controller can be synchronised to an external oscillator.

The LTC4268-1 includes a field-proven PD controller front end for worry-free use in hostile PoE environments.

By incorporating a precision dual current limit, the LTC4268-1 ensures trouble-free interoperability with any power sourcing equipment (PSE).

The LTC4268-1 is capable of handling 750mA with the lowest on-resistance (typically 0.55ohm) Hot Swap MOSFET on the market.

The ultralow FET on-resistance minimises device heating and improves overall efficiency.

For even higher output power, the normal current limit can be disabled, allowing implementation of proprietary, ultra-high-power designs.

Specified over the commercial and industrial temperature ranges, the LTC4268-1 is offered in a space saving 32-pin 7 x 4mm thermally enhanced DFN package.