Linear Technology introduces the LTC4267, an IEEE 802.3af Power over Ethernet (PoE) controller. He comes in a 3mm x 5mm DFN package, ensures compliance with the IEEE 802.3af PoE standard and includes an onboard 25kOhm signature resistor and classification current source. The internal 100V power MOSFET provides protection against inductive voltage spikes from long cables, while the guaranteed low leakage prevents corruption of the 25kOhm signature resistance. The chip dual-level inrush current limit allows for seamless interface with legacy PoE systems. The LTC4267 fits in PDs, like digital voice-over-IP phones, network wireless access points, security cameras, or any small Ethernet-connected device that requires less than 13W. The device includes an onboard constant-frequency current mode DC/DC controller. Slope compensation can be programmed with external resistors to allow for fast transient response with minimum output capacitance. By integrating the switching regulator, the chip simplifies PD design. Specified over the commercial and industrial temperature grades, pricing for the LTC4267 begins at 2.10$ each for 1,000-piece quantities.
