Analog Devices Inc./Maxim Integrated MAX14945EWE+T

Overview

MAX14945EWE+T from Maxim Integrated is a 2.75kVRMS galvanically isolated half-duplex RS-485/RS-422 transceiver with integrated LDO, ±30kV HBM ESD protection on cable-side pins (A/B), and true fail-safe receiver. It operates from 1.71V–5.5V logic supply (VDDA) and 4.5V–5.5V isolated supply (VDDB), supports up to 500kbps data rate, and enables robust industrial bus communication in ground-noise-prone environments such as PLC backplanes.

For engineers reviewing the MAX14945EWE+T datasheet, MAX14945EWE+T pinout, MAX14945EWE+T application, or MAX14945EWE+T equivalent, key selection criteria include isolation voltage rating (2750VRMS/60s), bus loading capability (1/8-unit load, 256-node support), integrated LDO output (5V, 300mA), thermal shutdown threshold (+160°C), and common-mode transient immunity (35kV/μs).

Technical Context

The MAX14945EWE+T implements capacitive galvanic isolation across a reinforced barrier, separating UART-side (GNDA/VDDA) and cable-side (GNDB/VDDB/VLDO) domains. Its driver uses foldback current limiting and thermal shutdown for fault resilience, while the receiver features fixed differential thresholds (–200mV to –50mV) and internal 5kΩ SBA pullup.

It integrates a 5V LDO (VLDO input ≥4.68V) delivering up to 300mA to VDDB, eliminating need for external isolated power. The device complies with RS-485 EIA/TIA-485, withstands ±10kV IEC 61000-4-5 surge, and guarantees logic-high RXD under open/shorted bus conditions via true fail-safe circuitry.

Key Specifications

Pinout & Package

MAX14945EWE+T is housed in a wide-body 16-pin SOIC (W16M+9) package with 8mm creepage and clearance, RoHS-compliant, and rated for 2750VRMS isolation. Pin 1 is VDDA; pins 2 and 8 are GNDA; pins 9 and 15 are GNDB; pins 10 and 14 are no-connect; all other pins serve defined UART- or cable-side functions.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ADM2483BRWZ and ISO1500DWR, the MAX14945EWE+T uniquely combines 2750VRMS isolation, integrated 5V/300mA LDO, true fail-safe, and SBA monitoring-reducing system-level component count and improving diagnostics in multi-node industrial networks.

Availability

MAX14945EWE+T is available at Aetrix Electronics and suitable for industrial automation, programmable logic controller (PLC) backplanes, and smart energy metering requiring stable component supply, long-term lifecycle assurance, and RoHS-compliant packaging.

Supply support for MAX14945EWE+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 high-reliability semiconductor solutions for industrial, automotive, and communications markets.

The MAX14945EWE+T belongs to Maxim's isolated interface product line, engineered specifically for noise-immune, ground-loop-free RS-485/RS-422 communication in harsh industrial environments where safety certification and long-term reliability are mandatory.

FAQ

What is the isolation voltage rating of the MAX14945EWE+T and how is it certified?

The MAX14945EWE+T is rated for 2750VRMS galvanic isolation for 60 seconds and certified to UL1577 and CSA Bulletin 5A. It achieves this via integrated high-voltage capacitors forming a reinforced insulation barrier between GNDA and GNDB domains. Partial discharge testing confirms <5pC at 1182VP, and it meets IEC 60747-5-5 requirements for VIORM (630VPEAK) and VIOWM (445VRMS).

Does the MAX14945EWE+T require an external isolated power supply?

No - the MAX14945EWE+T includes an integrated low-dropout regulator that accepts 4.68V–14V on VLDO (relative to GNDB) and delivers a regulated 5V ±5% output at up to 300mA on VDDB. This eliminates the need for an external isolated DC/DC converter in most applications, though VDDB can also be driven directly if the LDO is disabled by leaving VLDO unconnected or tying it to GNDB.

How does the MAX14945EWE+T ensure reliable operation on noisy RS-485 buses?

The MAX14945EWE+T ensures reliability through multiple mechanisms: true fail-safe receiver (guaranteed logic-high RXD on open/shorted lines), ±30kV HBM ESD protection on A/B pins, 35kV/μs common-mode transient immunity, thermal shutdown at +160°C, and foldback current limiting on driver outputs. Its 1/8-unit load receiver also minimizes bus loading, supporting up to 256 nodes without signal degradation.

What is the function of the SBA pin on the MAX14945EWE+T?

The SBA (Side-B Active) pin on the MAX14945EWE+T is an open-drain output with an internal 5kΩ pullup to VDDA. It asserts low only when the cable-side power (VDDB) is present and within operational limits - providing hardware-level confirmation that isolation and bus-side circuitry are powered and functional. This enables safe initialization sequences and fault diagnostics in systems like PLCs and smart meters.

Can the MAX14945EWE+T operate at data rates higher than 500kbps?

No - the MAX14945EWE+T is specified for a maximum data rate of 500kbps, verified across temperature and supply voltage ranges. Attempting higher rates may cause timing violations, increased bit error rate, or failure to meet RS-485 standard compliance due to propagation delay skew (144ns max) and driver rise/fall times (900ns). For >500kbps applications, consider non-isolated or higher-speed isolated alternatives like the ISO1500DWR (1Mbps), noting trade-offs in bus loading and fail-safe behavior.