Analog Devices Inc./Maxim Integrated MAX5922CEUI+T

Overview

MAX5922CEUI+T 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), programmable current limit (via external R_SENSE), and provides POK/ZC/FAULT status outputs. It is used in midspan PoE injectors delivering power over spare pairs in Ethernet infrastructure.

For engineers reviewing the MAX5922CEUI+T datasheet, MAX5922CEUI+T pinout, MAX5922CEUI+T application, or MAX5922CEUI+T equivalent, key selection criteria include IEEE 802.3af compliance, midspan detection collision avoidance (enabled by default in MAX5922C), UVLO threshold of 28V, zero-current detection with 3.75mV threshold, and 28-pin TSSOP package with separate analog/digital grounds.

Technical Context

The MAX5922CEUI+T implements full IEEE 802.3af PSE functionality in three sequential modes: detection (VPBI = 4V, VPBII = 8V, t_DET = 196ms max), classification (V_CLASS = 28V, t_CLASS = 26ms max), and power delivery with slew-rate-controlled startup (dV_OUT/dt ≤ 100 V/ms). Its integrated MOSFET features 0.45Ω R_DS(ON) at +25°C and supports up to 0.8A continuous drain current.

It includes dedicated analog and digital ground domains (±4V offset tolerance), detection collision avoidance permanently enabled (per MAX5922C variant), and fault management configurable for latch-off or autorestart (t_RESTART = 1.92s typical). Zero-current detection activates after POK assertion and triggers ZC output after 350ms deglitched low-current condition.

Key Specifications

Pinout & Package

MAX5922CEUI+T is housed in a 28-pin TSSOP package (body size 4.4mm × 9.7mm, 0.65mm pitch) with exposed thermal pad. Pin 1 is marked by dot; pins 3, 6, and 26 are no-connect; AGND and DGND must be joined at a single point on PCB.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX5922AEUI+T, the MAX5922CEUI+T offers lower UVLO (28V vs. 38V) and always-enabled DCA-ideal for midspan systems with variable input and shared cabling. Versus LT4275AIMSE#TRPBF, it delivers simpler integration (integrated FET) but lacks PoE+ capability and higher-power classification.

Availability

MAX5922CEUI+T is available at Aetrix Electronics and suitable for midspan power injectors, single-port PoE adapters, computer telephony gateways, and industrial Ethernet nodes requiring stable component supply and full IEEE 802.3af compliance.

Supply support for MAX5922CEUI+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 MAX5922 product line delivers fully integrated, standards-compliant PSE controllers targeting cost-sensitive, space-constrained Ethernet infrastructure equipment requiring minimal external components and robust fault handling.

FAQ

What is the UVLO threshold for MAX5922CEUI+T and how is it set?

The MAX5922CEUI+T has a fixed undervoltage lockout threshold of 28V (min 26V, max 30V), internally trimmed and not adjustable. This ensures the device remains in shutdown until the +32V to +60V input rail stabilizes above the minimum operational voltage required for reliable IEEE 802.3af detection. Unlike the MAX5922A variant, the MAX5922CEUI+T does not support external UVLO adjustment via the UVLO pin.

Does MAX5922CEUI+T support detection collision avoidance, and how is it configured?

Yes, MAX5922CEUI+T has detection collision avoidance permanently enabled per its C-grade specification. No external connection to the DCA pin is required-it functions automatically. When PD detection fails, the device enters a 2.8s high-impedance back-off period to avoid simultaneous probing by multiple midspan PSEs on the same cable segment, preventing false fault detection and ensuring interoperability in distributed PoE deployments.

How does MAX5922CEUI+T perform PD classification and what classes does it support?

The MAX5922CEUI+T executes IEEE 802.3af-compliant classification by applying 28V to the OUT pin and measuring current draw through an external 150Ω resistor on the RCL pin. It supports Classes 0–4 with defined current thresholds (e.g., Class 0: <6.5mA, Class 4: >33mA). Classification status is reported via CL0–CL2 open-drain outputs, and the process completes within 26ms after detection, enabling rapid power-up of compliant powered devices.

What is the role of the ZC_EN pin on MAX5922CEUI+T and when should it be asserted?

The ZC_EN pin on MAX5922CEUI+T enables or disables zero-current detection. When pulled high to VDIG, it activates the circuit that monitors for <3.75mV across RSENSE for ≥350ms-indicating a disconnected or faulty PD-and asserts the ZC output. It should be asserted in midspan applications where detecting unplugged devices is critical for system diagnostics and safety; leaving it low disables this function entirely.

Can MAX5922CEUI+T be used in both endspan and midspan PoE architectures?

Yes, MAX5922CEUI+T supports both architectures. In endspan (switch-integrated) mode, it powers PDs over signal pairs using standard Ethernet magnetics. In midspan mode, it delivers power over spare pairs and leverages its permanently enabled DCA feature to prevent contention. The device's dual-ground architecture (AGND/DGND ±4V offset) and wide +32V to +60V input range make it adaptable to either topology without hardware changes.