STMicroelectronics ST485ERXN

Overview

ST485ERXN from STMicroelectronics is a half-duplex, ±15 kV HBM ESD-protected RS-485/RS-422 transceiver in SO8 package, operating from a single 5 V supply with 300 µA quiescent current, 2.5 Mbps max data rate, and -7 V to +12 V common-mode input range. It integrates one driver and one receiver for multipoint bus communication in industrial automation networks.

For engineers reviewing the ST485ERXN datasheet, ST485ERXN pinout, ST485ERXN application, or ST485ERXN equivalent, key selection criteria include ESD robustness (±15 kV HBM), low-power operation (300 µA typ.), driver thermal shutdown, receiver hysteresis (70 mV typ.), and compatibility with legacy RS-485 infrastructure requiring up to 64 nodes.

Technical Context

The ST485ERXN implements a true half-duplex transceiver architecture with independent enable controls: DE (driver enable) and RE (receiver enable), allowing precise bus arbitration. Its driver features short-circuit current limiting and thermal shutdown, forcing outputs into high-impedance state during overload - critical for fault-tolerant fieldbus systems.

The receiver delivers 70 mV typical hysteresis and supports -7 V to +12 V common-mode voltage, enabling reliable operation in electrically noisy industrial environments with ground potential differences. Propagation delay is 30 ns (typ.) with 5 ns skew, supporting timing-critical 2.5 Mbps data transmission over twisted-pair lines.

Key Specifications

Pinout & Package

ST485ERXN is housed in an industry-standard SO8 (Small Outline 8-pin) package, RoHS-compliant and ECOPACK® certified, with 1.27 mm pitch and surface-mount footprint compatible with automated PCB assembly.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX13487EESA+ and SN65HVD72DR, ST485ERXN uniquely balances 2.5 Mbps speed, ±15 kV ESD, thermal shutdown, and 300 µA quiescent current - making it optimal for general-purpose industrial RS-485 nodes where robustness and moderate throughput coexist.

Availability

ST485ERXN is available at Aetrix Electronics and suitable for industrial PLC backplanes, building automation networks, motor drive feedback interfaces, and energy meter concentrators requiring stable component supply across extended product lifecycles.

Supply support for ST485ERXN 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing microcontrollers, power ICs, sensors, and analog/mixed-signal products for industrial, automotive, and consumer markets.

The ST485ERXN belongs to ST's RS-485 transceiver portfolio, engineered specifically for rugged, low-power, multi-drop industrial communications where ESD resilience, thermal reliability, and timing precision are non-negotiable.

FAQ

What is the maximum recommended bus length for ST485ERXN at 2.5 Mbps?

At 2.5 Mbps, STMicroelectronics specifies a maximum bus length of 100 meters using standard 120 Ω twisted-pair cable with proper termination. Longer distances require reduced data rates - e.g., 1200 meters at 100 kbps - due to signal attenuation and reflection constraints inherent to RS-485 physical layer design.

Does ST485ERXN support automatic direction control (auto-RS485)?

No, ST485ERXN does not integrate automatic direction control logic. It requires external microcontroller GPIOs to coordinate DE and RE signals for half-duplex operation. Direction switching must be software-managed with appropriate dead-time insertion to prevent bus contention during transitions.

Can ST485ERXN operate with a 3.3 V supply?

No, ST485ERXN is specified only for 5 V ±5% operation. The absolute maximum VCC is 7 V, and DC characteristics (e.g., VIH/VIL thresholds, driver output swing) are characterized exclusively at 5 V. Using 3.3 V will result in undefined behavior, insufficient output voltage margins, and potential receiver malfunction.

Is external termination required on the RS-485 bus when using ST485ERXN?

Yes, a 120 Ω termination resistor must be placed across the A and B lines at both ends of the bus to prevent signal reflections. ST485ERXN does not include internal termination; omitting external termination causes data corruption at speeds above ~100 kbps or on cables longer than 10 meters.