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 54 V supply. In addition, it supports 2-event classification and new Class 5 classification of high-power PDs. The MAX5971B provides up to 40 W to a single port (Class 5 enabled) and still provides high-capacitance detection for legacy PDs.

The device provides four operating modes to suit different system requirements. By default, auto mode allows the device to operate automatically at its default settings without any software. Semi-automatic mode automatically detects and classifies a device connected to the port after initial software activation, but does not power the port until instructed to by software. Manual mode allows total software control of the device and is useful for system diagnostics. Shutdown mode terminates all port activities and securely turns off power to the port.

The IC features an I²C-compatible, 2-wire serial interface, and is fully software-configurable and programmable. The device provides instantaneous readout of port current through the I²C interface. The device’s extensive programmability enhances system flexibility, enables field diagnosis and allows for uses in other, non-standard applications.

The device provides input undervoltage lockout (UVLO), input undervoltage detection, input overvoltage lockout, overtemperature protection, output voltage slew-rate limit during startup, and LED status indication. The MAX5971B programmability includes startup timeout, overcurrent timeout, and load-disconnect detection timeout.

The device is available in a space-saving, 28-pin TQFN (5 mm x 5 mm) power package and is rated for the extended (-40°C to +85°C) temperature range.