Analog Devices Inc./Maxim Integrated MAX5945EAX+T

Overview

MAX5945EAX+T from Maxim Integrated is a quad IEEE 802.3af-compliant network power controller for Power-Sourcing Equipment (PSE), delivering PD discovery, classification, programmable current-limit (212 mV sense threshold), DC/AC load disconnect detection, and I²C-compatible 3-wire serial control across four independent -48V Ethernet ports. It operates in endpoint or midspan PSE systems such as enterprise LAN switches and PoE injectors.

For engineers reviewing the MAX5945EAX+T datasheet, MAX5945EAX+T pinout, MAX5945EAX+T application, or MAX5945EAX+T equivalent, key selection considerations include its -40°C to +85°C extended temperature rating, 36-pin SSOP package, autonomous/microcontroller-coordinated operation, watchdog-enabled fault recovery, and dual-mode (endpoint/midspan) PSE configurability.

Technical Context

The MAX5945EAX+T implements four independent port state machines with integrated analog sensing (SENSE1–4), gate drivers (GATE1–4), and detection/classification circuitry (DET1–4) to execute IEEE 802.3af-compliant PD handshake sequences-including two-phase detection (3.8–4.2V / 9.0–9.6V probe voltages) and classification (16–20V probe, 50–75mA current thresholds). Each port supports programmable startup timeout (50–70ms), overcurrent fault window (50–70ms), and foldback current limiting (VFLBK_ST = 30V, VFLBK_END = 50V).

Its I²C-compatible interface uses separate SDAIN/SDAOUT lines for optocoupler isolation, with 16 unique slave addresses set via A0–A3 inputs. Hardware features include dedicated SHD1–SHD4 shutdown pins, RESET input with 300µs minimum pulse, INT open-drain fault indicator, MIDSPAN mode select, and OSC_IN-based AC disconnect monitoring (300–350µA threshold, 2.2V fail threshold).

Key Specifications

Pinout & Package

MAX5945EAX+T is housed in a 36-pin Small Outline Skirted Package (SSOP), with exposed thermal pad not electrically connected. Pin pitch is 0.025", body width 0.209", and maximum height 1.75mm - compatible with IPC-7351B SOIC-36 footprint variants.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LTC4259AIDE#PBF, MAX5945EAX+T adds hardware-accelerated AC disconnect and midspan cadence timing; versus TPS23754PWPR, it provides unified quad-port control with I²C configurability and broader temperature range - making it optimal for scalable, software-managed PSE platforms.

Availability

MAX5945EAX+T is available at Aetrix Electronics and suitable for enterprise switching, midspan injection, industrial IoT gateways, outdoor wireless infrastructure, and telecom backhaul systems requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX5945EAX+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 MAX5945EAX+T belongs to Maxim's Power-over-Ethernet PSE controller product line, engineered specifically to simplify IEEE 802.3af-compliant multi-port power sourcing in space-constrained, thermally challenging networking equipment.

FAQ

What is the operating voltage range for the analog supply (VEE) of the MAX5945EAX+T?

The MAX5945EAX+T supports an analog supply range of -32V to -60V on VEE relative to AGND, with guaranteed operation across the full -48V PoE standard range. Its VEE undervoltage lockout activates at 28.5V (AGND–VEE), and overvoltage protection triggers at 62.5V, providing robust rail supervision for telecom-grade -48V systems.

How does the MAX5945EAX+T implement IEEE 802.3af-compliant PD classification?

The MAX5945EAX+T performs classification by applying 16–20V across the PD signature resistor via DET1–DET4 and measuring current through the same node. It recognizes classes 0–4 using programmable thresholds (e.g., 50–75mA for class 0–4), with default values matching IEEE 802.3af Table 33–7. Classification completes within 40ms and is fully configurable via I²C registers.

Can the MAX5945EAX+T operate in both endpoint and midspan PSE configurations?

Yes, the MAX5945EAX+T supports both configurations: endpoint mode (default) via MIDSPAN pin low, and midspan mode when MIDSPAN is pulled high. In midspan mode, it enforces IEEE 802.3af cadence timing (2.4s inter-port delay) and uses OSC_IN for AC disconnect detection - all handled in hardware without firmware overhead.

What protection features does the MAX5945EAX+T provide against overcurrent events?

The MAX5945EAX+T provides multi-layer overcurrent protection: initial current-limit clamp at 212mV VSENSE, foldback limiting that reduces trip threshold as OUT–VEE rises from 30V to 50V, short-circuit detection via VDCP <1.62V, and programmable fault timeout (50–70ms). It also includes class-overcurrent detection to flag PDs drawing excess current for their assigned class.

Is the MAX5945EAX+T pin-compatible with any other Maxim PSE controllers?

Yes, the MAX5945EAX+T is pin- and function-compatible with the LTC4259AIDE#PBF, sharing identical pinout, register mapping, and electrical specifications. This allows direct replacement in existing designs while adding optional features like OSC_IN-based AC disconnect and enhanced midspan timing control.