Analog Devices Inc./Maxim Integrated MAX5940BESA+T

Overview

The MAX5940BESA+T from Maxim Integrated is an IEEE 802.3af-compliant powered device (PD) interface controller for Power-over-Ethernet systems, integrating detection signature, programmable classification, and an isolation N-channel MOSFET with 0.8Ω on-resistance at +85°C. It features adjustable undervoltage lockout (UVLO) with 7.4V hysteresis, dual PGOOD/PGOOD outputs, and supports -40°C to +85°C operation in 8-pin SO package. Used in IP phones and security cameras to manage PoE power handshaking and inrush control.

For engineers reviewing the MAX5940BESA+T datasheet, MAX5940BESA+T pinout, MAX5940BESA+T application, or MAX5940BESA+T equivalent, this page delivers verified technical context, exact pin functions, real-world timing behavior under twisted-pair voltage drop, confirmed UVLO adjustability via external resistor-divider, and validated alternatives for PoE PD design continuity.

Technical Context

The MAX5940BESA+T operates in three distinct modes-detection (1.4V–10.1V), classification (12.6V–20V), and power mode-with leakage current <10µA during detection and programmable classification current up to 41.4mA (Class 4). Its internal N-channel MOSFET enables isolation and inrush limiting via GATE-controlled gate-charge current (10µA typ) and external CGATE capacitor.

UVLO threshold is adjustable from 12V to 67V using a 25.5kΩ ±1% resistor-divider on the UVLO pin, with 20% hysteresis referenced to 2.46V internal reference; power-mode transition includes 0.32ms deglitch time to reject cable-induced glitches and ensure stable detection→classification→power-on sequencing.

Key Specifications

Pinout & Package

MAX5940BESA+T is housed in an 8-pin SOIC-N package (JEDEC MS-012) with 1.27mm pitch, 3.9mm body width, and exposed pad not present. Pin 1 is located at top-left per standard SO marking convention.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX5940DESA+, the MAX5940BESA+T trades 10V absolute max rating for tighter cost control and identical 80V operational headroom; versus LT4275IMS#PBF, it retains external CGATE flexibility for fine-grained inrush tuning but requires one extra capacitor.

Availability

MAX5940BESA+T is available at Aetrix Electronics and suitable for IP phones, security cameras, wireless access nodes, and computer telephony systems requiring stable component supply across multi-year production cycles and PoE infrastructure upgrades.

Supply support for MAX5940BESA+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 industrial, communications, and computing applications, with emphasis on high-reliability, low-power, and integration-rich solutions.

The MAX5940BESA+T belongs to Maxim's Power-over-Ethernet PD interface controller family, engineered specifically to simplify IEEE 802.3af compliance in endpoint devices by integrating detection, classification, isolation switching, and power sequencing in a single SOIC package.

FAQ

What is the absolute maximum voltage rating for MAX5940BESA+T?

The MAX5940BESA+T has an absolute maximum rating of 80V on the GND pin relative to VEE. This is specified in the Absolute Maximum Ratings table and distinguishes it from the MAX5940D variant (90V). Exceeding 80V may cause permanent damage, even briefly, and the device is designed to operate continuously up to 67V input (VIN = GND – VEE).

Does MAX5940BESA+T support bridgeless PoE front-end configurations?

Yes, MAX5940BESA+T is explicitly designed to work with or without an external diode bridge. Its detection and classification circuitry operates correctly across both signal-pair and spare-pair PoE delivery methods, eliminating forward-voltage loss and thermal stress associated with bridge rectifiers in space- or efficiency-sensitive designs.

How is the UVLO threshold adjusted on MAX5940BESA+T?

The UVLO threshold on MAX5940BESA+T is adjusted using an external resistor-divider connected between GND and VEE, with the UVLO pin tied to the midpoint. The total resistance must equal 25.5kΩ ±1%; the threshold voltage is set by the divider ratio relative to the internal 2.46V reference, enabling precise turn-on/turn-off points from 12V to 67V.

What is the function of the GATE pin on MAX5940BESA+T?

The GATE pin on MAX5940BESA+T sources a constant 10µA current to charge the gate of the internal N-channel MOSFET, controlling the rate of V_DS rise and thus limiting inrush current. An external capacitor (CGATE) from GATE to OUT sets the soft-start time; pulling GATE to VEE disables the MOSFET while preserving detection/classification functionality.

Can MAX5940BESA+T be used in Class 4 PoE applications?

Yes, MAX5940BESA+T supports Class 4 classification with RCL = 178Ω, delivering 36.6–41.4mA classification current per IEEE 802.3af Table 2. However, Class 4 is reserved for future use in the standard and requires PSE support; the device itself fully implements the required signature and timing behavior.