The LT4276AIUFD#PBF from Analog Devices is a IEEE 802.3 af/at-Compliant Powered Device Controller IC that is ideal for high power wireless data systems, outdoor security camera equipments, commercial and public information displays, and high temperature applications. It requires an input voltage of up to 60 V and delivers an output power of 90 W. This controller consists of a switching regulator controller, current fault comparators, powered device (PD) interface controller, temperature shutdown (TSD), startup regulator, internal buck controller, load comparator, oscillator, current sources, MOSFETs, and other passive components. It provides a synchronous operation in both forward and flyback topologies with a support for auxiliary power supply. This power-over-ethernet (PoE) controller employs the LTPoE++ classification scheme to detect and classify the PD based on the class, and then delivers the required output power at the correct PD RJ45 connector port. It also offers backwards compatibility with other IEEE 802.3-compliant devices.

This PoE controller does not require an opto-isolator for flyback operation due to internal topology support, greatly simplifying the design. It uses a resistor divider to accurately sense the auxiliary input voltage appearing at the AUX pin. This controller ensures hot swap function with the external N-channel MOSFET while maximizing efficiency, reducing heat dissipation, and easing the thermal design. It is available in a surface-mount package that measures 4 x 5 mm.