The MAX5971B is a single-port power controller designed for use in IEEE® 802.3af/at-compliant power-sourcing equipment (PSE). This device provides powered device (PD) discovery, classification, current limit, and DC and AC load-disconnect detections. The MAX5971B supports both fully automatic operation and software programmability, and features an integrated power MOSFET and sense resistor. The device supports detection and classification operation from a single 54V supply. In addition, it supports 2-event classification and new Class 5 classification of high-power PDs. The MAX5971B provides up to 40W to a single port (Class 5 enabled) and still provides high-capacitance detection for legacy PDs.