Power Electronics

PoE Controller Integrates Switching Regulator

Linear Technology Corp.’s new LTC4267 is an IEEE 802.3af Power-over-Ethernet (PoE) controller that features an integrated switching regulator to greatly simplify powered device (PD) design. Offered in a space saving 3-mm x 5-mm DFN package, this IC ensures compliance with the IEEE 802.3af PoE standard and includes an onboard 25-kΩ signature resistor and classification current source. The internal 100-V power MOSFET provides protection against inductive voltage spikes from long cables, while the guaranteed low leakage prevents corruption of the 25-kΩ signature resistance. The LTC4267's dual-level inrush current limit allows for seamless interface with legacy PoE systems. The LTC4267 fits in PDs such as digital voice-over-IP phones, network wireless access points, security cameras or any small Ethernet-connected device that requires less than 13 W.

The LTC4267 includes an onboard constant-frequency current mode dc-dc controller, easily tailored to a wide variety of power supply voltage and load current requirements. Constant frequency operation is maintained down to very light loads, minimizing low-frequency noise generation. Slope compensation can be programmed with external resistors to allow for fast transient response with minimum output capacitance.

By integrating the switching regulator, the LTC4267 significantly simplifies PD design. With only the switching regulator's pass FET, a transformer and a few small components required externally, the LTC4267 provides the smallest PoE solution available.

Specified over the commercial and industrial temperature grades, pricing for the LTC4267 begins at $2.10 each for 1000-piece quantities

For more information, visit www.linear.com.

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