LINEAR Technology, represented in Australia by Soanar , has released the LTC4267, an IEEE 802.3af Power over Ethernet (PoE) controller with an integrated switching regulator.
It is offered in a 3mm x 5mm DFN package. The IC complies with the IEEE 802.3af PoE standard and includes an onboard 25kΩ signature resistor and classification current source. The internal 100V power MOSFET provides protection against inductive voltage spikes from long cables. Low leakage prevents corruption of the signature resistance. The LTC4267's dual-level inrush current limit allows for seamless interface with legacy PoE systems. It fits in digital voice-over-IP phones, network wireless access points, security cameras and small Ethernet-connected device that requires less than 13W.
The LTC4267 includes an onboard constant-frequency current mode dc/dc controller, easily tailored to a range of power supply voltage and load current requirements. Constant frequency operation is maintained down to very light loads, minimising low frequency noise generation. Slope compensation can be programmed with external resistors to allow for fast transient response with minimum output capacitance.