Analog Devices Inc./Maxim Integrated MAX14939GWE+

Overview

The MAX14939GWE+ from Maxim Integrated is a 2.75kVRMS galvanically isolated half-duplex RS-485/PROFIBUS-DP transceiver with integrated 5V LDO, ±35kV HBM ESD protection on A/B pins, 20Mbps data rate, and true fail-safe receiver. It enables robust industrial serial communication across ground-potential differences in programmable logic controllers and HVAC systems.

For engineers reviewing the MAX14939GWE+ datasheet, MAX14939GWE+ pinout, MAX14939GWE+ application, or MAX14939GWE+ equivalent, key selection criteria include isolation voltage rating (2750VRMS/60s), cable-side LDO capability (VLDO = 4.68–14V, VDDB = 4.5–5.5V), ¼-unit-load receiver (128-node bus support), thermal shutdown (+160°C), and CMTI of 35kV/μs.

Technical Context

This device implements capacitive galvanic isolation between UART-side (GNDA/VDDA) and cable-side (GNDB/VDDB) domains, enabling signal integrity in noisy industrial environments with large ground potential differentials. Its architecture integrates an isolated LDO (VLDO input → VDDB output) to power the RS-485 driver/receiver stage without external regulators.

The transceiver features dual protection layers: foldback current limiting for driver short-circuit events across ±7V to +12V common-mode range, and thermal shutdown that forces outputs to high-Z above +160°C junction temperature. Receiver thresholds are fixed at –200mV to –50mV with 15mV hysteresis, ensuring deterministic logic-high output during open/shorted bus conditions.

Key Specifications

Pinout & Package

MAX14939GWE+ is housed in a wide-body 16-pin SOIC package (W SOIC) with 8mm creepage and clearance, optimized for reinforced isolation in industrial PCB layouts.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar isolated RS-485 transceiver applications.

Compared with ADM2483BRWZ and ISO1500DWWR, the MAX14939GWE+ uniquely combines 2750VRMS/60s isolation, integrated 5V LDO, 20Mbps operation, and ¼-unit-load receiver-enabling simpler, more scalable, and more robust industrial bus designs without external power or bias components.

Availability

MAX14939GWE+ is available at Aetrix Electronics and suitable for industrial automation equipment, programmable logic controllers, and HVAC systems requiring stable component supply, long-term lifecycle support, and certified isolation performance.

Supply support for MAX14939GWE+ 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, automotive, and communications markets.

The MAX14939GWE+ belongs to Maxim's isolated interface product line, engineered specifically for high-reliability RS-485/PROFIBUS-DP communication in electrically noisy, ground-differential industrial environments.

FAQ

What is the isolation voltage rating of the MAX14939GWE+ and how is it certified?

The MAX14939GWE+ provides 2750VRMS galvanic isolation for 60 seconds, certified to UL1577 and CSA Bulletin 5A standards. It achieves this via on-chip high-voltage capacitors and meets IEC 60747-5-5 requirements for VIORM (630VPEAK), VIOWM (445VRMS), and partial discharge (1182VP). This rating ensures safe operation in industrial mains-connected equipment.

Does the MAX14939GWE+ require external power for the isolated RS-485 side?

No - the MAX14939GWE+ includes an integrated LDO that generates VDDB = 4.5–5.5V from a VLDO input of 4.68–14V. When VLDO is supplied, VDDB powers the driver/receiver stage and can source up to 10mA for external termination. If the LDO is not used, connect VLDO to GNDB and apply +5V directly to VDDB.

How does the MAX14939GWE+ handle open or shorted RS-485 bus lines?

The MAX14939GWE+ implements true fail-safe receiver circuitry: when A/B inputs are open, shorted, or connected to a terminated idle bus, RXD outputs a guaranteed logic-high state. This is achieved via fixed receiver thresholds (–200mV to –50mV) and internal biasing - eliminating the need for external fail-safe resistors.

What is the maximum number of MAX14939GWE+ devices supported on a single RS-485 bus?

The MAX14939GWE+ features a ¼-unit-load receiver input impedance, allowing up to 128 transceivers on one RS-485 bus segment. This quadruples the node count versus standard 1-unit-load transceivers (limited to 32 nodes), reducing repeater requirements and simplifying large-scale industrial network topologies.

What protection features does the MAX14939GWE+ include against electrical overstress?

The MAX14939GWE+ integrates multiple protection layers: ±35kV HBM ESD on A/B pins to GNDB, ±10kV IEC 61000-4-5 surge immunity, foldback current limiting on driver outputs, and thermal shutdown at +160°C. These features collectively prevent latch-up, permanent damage, or communication failure during handling, installation, or field operation.