STMicroelectronics ST485ERXDR

Overview

ST485ERXDR from STMicroelectronics is a half-duplex, ±15 kV HBM ESD-protected RS-485/RS-422 transceiver in SO-8 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 and building control systems.

For engineers reviewing the ST485ERXDR datasheet, ST485ERXDR pinout, ST485ERXDR application, or ST485ERXDR 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 SO-8 footprint compatibility with legacy RS-485 designs.

Technical Context

The ST485ERXDR implements a fail-safe receiver with 70 mV typical hysteresis and differential threshold of ±0.2 V over -7 V to +12 V common-mode range, enabling reliable signal detection in noisy industrial environments. Its driver features short-circuit current limiting and thermal shutdown, forcing outputs into high-impedance state during overload - critical for bus integrity in multi-node networks.

Control logic uses independent DE (driver enable) and RE (receiver enable) pins to support half-duplex timing control, with propagation delays of 30 ns (driver) and 130 ns (receiver) and skew ≤5 ns (driver) / ≤13 ns (receiver). The device supports up to 64 unit loads on a single bus, meeting RS-485 standard loading requirements.

Key Specifications

Pinout & Package

ST485ERXDR is housed in an SO-8 (Small Outline, 8-pin) package with 1.27 mm pitch, ECOPACK®-compliant, suitable for automated SMT assembly and reflow profiles per JEDEC J-STD-020.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX3072EESA+ and SN65HVD72DR, ST485ERXDR uniquely balances ultra-low ICC (300 µA), integrated thermal shutdown, and ±15 kV ESD - making it optimal for cost-sensitive, reliability-critical industrial nodes where both power and robustness matter.

Availability

ST485ERXDR is available at Aetrix Electronics and suitable for industrial PLC backplanes, smart meter concentrators, and building automation controllers requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for ST485ERXDR 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 analog, microcontroller, power, and sensor solutions for industrial, automotive, and consumer markets.

The ST485 series belongs to ST's industrial interface portfolio, engineered specifically for ruggedized RS-485/RS-422 communication in harsh electrical environments - emphasizing ESD resilience, thermal safety, and interoperability across multi-vendor networks.

FAQ

Does ST485ERXDR support full-duplex RS-422 operation?

No. ST485ERXDR is a half-duplex transceiver with shared A/B bus terminals and separate DE/RE control lines. It lacks independent transmitter and receiver differential pairs required for simultaneous two-way RS-422 communication. For full-duplex, ST offers the ST3485 or ST75176 families.

What is the maximum cable length supported at 2.5 Mbps?

At 2.5 Mbps, ST485ERXDR supports up to 100 m over standard 120 Ω twisted-pair cable (e.g., Belden 9841), based on signal integrity limits defined in TIA/EIA-485-A. Longer distances require reduced data rates - e.g., 1200 m at 100 kbps - due to attenuation and reflection constraints.

Can ST485ERXDR be used without external termination resistors?

Yes, but only for short stubs (<10 cm) and low node counts (<8). For reliable operation beyond 50 cm or with >16 nodes, a 120 Ω termination resistor must be placed across A and B at each bus end to prevent reflections and ensure signal integrity per RS-485 standards.

Is ST485ERXDR compatible with 3.3 V logic interfaces?

Yes - its DI, DE, and RE inputs accept 3.3 V logic levels (VIH ≥ 2.0 V, VIL ≤ 0.8 V), and RO output swings rail-to-rail (0–5 V) but is CMOS-compatible with 3.3 V receivers when series-resistor limited or interfaced via level-shifter. VCC must remain at 5 V for specified performance.