Analog Devices Inc./Maxim Integrated MAX5971BETI+T

Overview

MAX5971BETI+T from Maxim Integrated is a single-port IEEE 802.3af/at-compliant Power Sourcing Equipment (PSE) controller with integrated power MOSFET and sense resistor, supporting up to 40W per port (Class 5 enabled), 54V single-supply operation, and I²C-compatible 2-wire serial interface for real-time port current readout. It performs PD discovery, classification (including 2-event and Class 5), DC/AC load-disconnect detection, and operates across –40°C to +105°C in endpoint or midspan PSE applications such as PoE injectors.

For engineers reviewing the MAX5971BETI+T datasheet, MAX5971BETI+T pinout, MAX5971BETI+T application, or MAX5971BETI+T equivalent, this page delivers verified technical context, exact pin functions, confirmed operating modes (auto/semi-auto/manual/shutdown), validated thermal and overvoltage protection thresholds, and real-world design implications of its programmable current limits and foldback behavior.

Technical Context

The MAX5971BETI+T implements a fully integrated PSE control architecture with on-die DMOS FET (R_DS(ON) = 0.5–1.3 Ω), internal current-sense resistor, and analog front-end for detection (V_DPH1 = 4.0 V, V_DPH2 = 9.3 V), classification (V_CL = 16–20 V), and AC/DC disconnect monitoring (I_{AC_TH} = 130 µA, I_{DC_TH} = 7.5 mA). Its digital core includes a 9-bit ADC (±3% gain error, 1.95 mA/LSB) and register-mapped I²C interface (up to 400 kHz) enabling full software control of startup timeout, fault recovery, and Class 5 current-limit configuration via ILIM1/ILIM2 pins and ICUT register.

Four operational modes-auto (default), semi-automatic, manual, and shutdown-are managed by EN, MIDSPAN, and LEGACY inputs, with latched logic states post-reset. Protection features include VEE UVLO (28.5 V, 3 V hysteresis), overvoltage lockout (62.5 V), thermal shutdown (150°C, 20°C hysteresis), and slew-rate-limited output startup-all implemented without external components beyond bypass capacitors and RC networks for AC disconnect.

Key Specifications

Pinout & Package

MAX5971BETI+T is housed in a 28-pin thermally enhanced TQFN package (5 mm × 5 mm, 0.5 mm pitch) with exposed pad (EP) connected to VEE for low thermal resistance (θ_JC = 2°C/W). The package is rated for –40°C to +105°C ambient operation and requires standard QFN PCB layout practices including EP solder paste stencil and thermal vias.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar PSE controller applications.

Compared with MAX5972BETI+, MAX5971BETI+T adds Class 5 support, programmable current limits, and higher 40W capability-critical for next-gen PoE devices-while sharing footprint and software interface. Against TPS23754PWPR, it reduces BOM count and layout complexity via integration but trades off vendor-specific toolchain flexibility.

Availability

MAX5971BETI+T is available at Aetrix Electronics and suitable for PoE injectors, enterprise switches, and industrial embedded PSE applications requiring stable component supply, extended temperature operation, and IEEE 802.3at compliance.

Supply support for MAX5971BETI+T includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Maxim Integrated, now part of Analog Devices, designs precision analog, mixed-signal, and power management ICs for demanding industrial, communications, and computing applications.

The MAX5971B product line delivers fully integrated, software-configurable PSE controllers targeting single-port IEEE 802.3af/at endpoints and midspans-designed to reduce system cost, accelerate time-to-market, and eliminate external discrete power stage components.

FAQ

What is the maximum power delivery capability of the MAX5971BETI+T?

The MAX5971BETI+T delivers up to 40W per port when Class 5 PD detection and classification are enabled, meeting IEEE 802.3at Type 2 requirements. This is achieved using its integrated DMOS FET and programmable current limit (up to 998 mA), with thermal protection ensuring safe operation under sustained load. The MAX5971BETI+T maintains backward compatibility with lower classes (0–4) and legacy PDs.

How does the MAX5971BETI+T handle AC versus DC load-disconnect detection?

The MAX5971BETI+T supports both AC and DC load-disconnect detection via dedicated circuitry. AC disconnect uses the OSC pin's triangular wave and DET pin current sensing (I_{AC_TH} = 130 µA typical), while DC disconnect monitors steady-state load current (I_{DC_TH} = 7.5 mA). Selection is hardware-configured via OSC pin connection-tied to VEE for DC mode, bypassed with 100 nF capacitor for AC mode-and both use the same tDISC timer (400 ms default).

Can the MAX5971BETI+T operate in both endpoint and midspan PSE topologies?

Yes, the MAX5971BETI+T supports both endpoint and midspan configurations via the MIDSPAN pin. When left unconnected, it activates collision-avoidance circuitry for midspan use; pulling MIDSPAN low configures endpoint mode. The device auto-detects topology during initialization and adjusts detection timing (e.g., tDMID = 2.2 s in midspan) and voltage probing accordingly-no firmware changes required.

What protection features are built into the MAX5971BETI+T?

The MAX5971BETI+T integrates VEE undervoltage lockout (28.5 V), overvoltage lockout (62.5 V), overtemperature shutdown (150°C), output slew-rate limiting, short-circuit detection (V_DCP = 1 V), and foldback current limiting. All protections trigger automatic port shutdown and generate an interrupt on the INT pin. These functions require no external components beyond recommended bypass capacitors and RC networks for AC disconnect.

Is the MAX5971BETI+T compatible with legacy 802.3af PDs?

Yes, the MAX5971BETI+T provides high-capacitance detection (up to 10 µF) and supports standard 25 kΩ resistor-based legacy PD identification. Its detection algorithm tolerates wide capacitance ranges and validates PD signature before power application. The LEGACY pin can be left unconnected to enable this mode, ensuring interoperability with all IEEE 802.3af-compliant devices while still supporting newer 802.3at Class 5 PDs.