Features and Benefits

  • IEEE 802.3af/at Compliant
  • Up to 40W for Single-Port PSE Applications
  • Integrated Power MOSFET and Sense Resistor
  • Supports 54V Single-Supply Operation
  • PD Detection and Classification
  • I2C-Compatible, 2-Wire Serial Interface
  • Instantaneous Readout of Port Current Through I2C Interface
  • Programmable Current Limit for Class 5 PDs
  • High-Capacitance Detection for Legacy Devices
  • Supports Both DC and AC Load Removal Detections
  • Current Foldback and Duty-Cycle-Controlled Current Limit
  • LED Indicator for Port Status
  • Direct Fast-Shutdown Control Capability
  • Space-Saving, 28-Pin TQFN (5mm x 5mm) Power Package

Product Details

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.

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 (5mm x 5mm) power package and is rated for the extended (-40°C to +85°C) temperature range.


  • Single-Port PSE End-Point Applications
  • Single-Port PSE Power Injectors (Midspan Applications)
  • Switches/Routers

Product Lifecycle icon-recommended Production

At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.

Evaluation Kits (1)

Tools & Simulations

Software Development

Reference Designs (1)

Product Recommendations

MAX5971B Companion Parts

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ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well.  "Zero defects" for shipped products is always our goal.

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Pricing displayed is based on 1-piece. The USA list pricing shown is for budgetary use only, shown in United States dollars (FOB USA per unit), and is subject to change. International prices may vary due to local duties, taxes, fees and exchange rates.