Analog Devices Inc./Maxim Integrated MAX5922AEUI+

Overview

MAX5922AEUI+ from Maxim Integrated is a single-port IEEE 802.3af-compliant power-sourcing equipment (PSE) controller with integrated 0.45Ω N-channel MOSFET, operating from +32V to +60V input. It performs PD detection (19kΩ–26.5kΩ signature), classification (Class 0–4), and current-limited power delivery with programmable UVLO (38V threshold), zero-current fault detection, and latch-or-autorestart fault management. It is used in midspan and endpoint PoE injectors for VoIP phones and IP cameras.

For engineers reviewing the MAX5922AEUI+ datasheet, MAX5922AEUI+ pinout, MAX5922AEUI+ application, or MAX5922AEUI+ equivalent, key selection considerations include IEEE 802.3af compliance, detection collision avoidance (enabled in MAX5922A), UVLO threshold (38V), integrated MOSFET R_DS(ON), and zero-current monitoring with ZC output.

Technical Context

The MAX5922AEUI+ implements full IEEE 802.3af PSE functionality across three sequential modes: detection (VPBI = 4V, VPBII = 8V, t_DET = 88ms), classification (V_CLASS = 28V, t_CLASS = 15–26ms), and power delivery with slew-rate-controlled startup (dV_OUT/dt ≤ 100 V/ms). Its analog-digital ground separation (±4V offset) and dedicated AGND_S sense path support robust noise immunity in high-voltage PoE systems.

It integrates a current-limit foldback circuit (V_FBSTOP = 18V), overcurrent timeout (t_OC = 50–75ms), thermal shutdown (+150°C), and detection collision avoidance with 2.8s back-off timing (DCA pin active). Fault signaling includes open-drain POK, ZC, and FAULT outputs referenced to DGND, each with defined delay and leakage specs.

Key Specifications

Pinout & Package

MAX5922AEUI+ is housed in a 28-pin TSSOP package (4.4mm × 9.7mm, 0.65mm pitch), rated for -40°C to +85°C operation. Thermal pad exposed on underside requires PCB solder connection for optimal power dissipation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar power-sourcing equipment applications.

Compared with LT4275AIMSE#PBF and NCP1095DR2G, MAX5922AEUI+ provides unique integration of detection collision avoidance, zero-current monitoring with deglitching, and a 0.45Ω MOSFET in one 28-pin TSSOP - reducing component count and simplifying midspan PSE design while maintaining strict 802.3af conformance.

Availability

MAX5922AEUI+ is available at Aetrix Electronics and suitable for VoIP phone power injectors, IP camera midspan systems, and wireless access point PSE modules requiring stable component supply, full IEEE 802.3af certification, and production-ready thermal performance.

Supply support for MAX5922AEUI+ 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) is a semiconductor company specializing in high-performance analog, mixed-signal, and power management ICs for industrial, communications, and computing applications.

The MAX5922 product line delivers fully integrated, single-port IEEE 802.3af PSE controllers targeting space-constrained, thermally demanding PoE infrastructure equipment such as compact injectors and switch add-on modules.

FAQ

What is the UVLO threshold for MAX5922AEUI+ and how is it set?

The MAX5922AEUI+ has a factory-set undervoltage lockout threshold of 38V (min 36V, max 40V) with 4.4V hysteresis. This fixed threshold eliminates external resistor divider components and ensures reliable startup above minimum PoE PSE supply voltage. The UVLO pin (Pin 8) is left floating to activate this default setting; connecting it to a resistive divider allows adjustment for nonstandard input rails.

Does MAX5922AEUI+ support midspan and endpoint PoE architectures?

Yes, MAX5922AEUI+ supports both architectures. In endpoint (switch/router) mode, it delivers power over data pairs; in midspan mode, it powers over spare pairs. Its DCA pin (Pin 25) enables collision avoidance timing critical for midspan use, and its separate AGND/DGND domains maintain signal integrity in noisy shared-cable environments.

How does MAX5922AEUI+ implement zero-current fault detection?

MAX5922AEUI+ monitors the voltage across R_SENSE to detect zero-current conditions. When V_OUT − V_DRAIN falls below 3.75mV (typ), the ZC_EN-enabled circuit asserts the ZC output low after a 350ms deglitched delay. This prevents nuisance tripping from transient load drops and confirms sustained open-circuit faults before signaling.

What is the role of the DCA pin on MAX5922AEUI+?

The DCA pin (Pin 25) activates hardware-based detection collision avoidance for midspan applications. When driven high, it enables a 2.8s back-off timer after failed PD detection cycles, preventing simultaneous probing by multiple PSEs on the same Ethernet segment. This feature is exclusive to MAX5922A/MAX5922C variants and is permanently disabled in MAX5922B.

Can MAX5922AEUI+ be used without external current-sensing resistors?

No. MAX5922AEUI+ requires an external 0.5Ω ±1% current-sense resistor (R_SENSE) connected between DRAIN and IN pins to set overcurrent protection, open-circuit detection, and current-limit foldback thresholds. Omitting R_SENSE disables all current-related safety functions and violates IEEE 802.3af compliance.