The MC34670 combines a Power Interface Port for IEEE 802.3af Powered Devices (PD) and a high performance current mode switching regulator. It allows a designer to build PDs with a minimum of external components by means of integrating the required IEEE 802.3af functions and all functions necessary to build a high efficiency DC/DC converter. On the PD side the 34670 fully supports the IEEE802.3af standard and provides complete signature and power classification functions. It controls inrush current limiting and incorporates adjustable undervoltage lockout. The switching regulator provides excellent line and load regulation. It drives an external Power MOSFET with sense resistor.