STMicroelectronics ST3485EBDR

Overview

ST3485EBDR from STMicroelectronics is a half-duplex, 3.3 V RS-485/RS-422 transceiver with ±15 kV IEC 61000-4-2 ESD protection, guaranteed 12 Mbps data rate, -7 to +12 V common-mode input range, and 1 µA shutdown current. It integrates one driver and one receiver in an SO8 package and is rated for -40 °C to +85 °C industrial operation-used in factory automation serial backbones requiring robust noise immunity and bus termination flexibility.

For engineers reviewing the ST3485EBDR datasheet, ST3485EBDR pinout, ST3485EBDR application, or ST3485EBDR equivalent, key selection criteria include its 3.3 V single-supply operation without charge pump, industry-standard 75176 pinout compatibility, thermal shutdown protection, floating-input fail-safe receiver, and support for up to 64 nodes on a multidrop bus.

Technical Context

This transceiver implements a half-duplex RS-485/RS-422 interface with independent driver enable (DE) and receiver enable (RE) controls, enabling precise bus arbitration. Its driver delivers ≥1.5 V differential output voltage into 54 Ω (RS-485) and supports short-circuit current limiting plus thermal shutdown.

The receiver features a ±0.2 V differential threshold with 70 mV hysteresis, guaranteed high output for open inputs, and 24 kΩ input resistance. Logic inputs (DE, RE, DI) operate at 3.3 V levels but are interoperable with 5 V systems via TTL-compatible thresholds (V_IL ≤ 0.8 V, V_IH ≥ 2.0 V).

Key Specifications

Pinout & Package

ST3485EBDR uses an SO8 (Small Outline 8-pin) package with standard 1.27 mm pitch, 4.9 mm × 6.0 mm body, and ECOPACK® RoHS-compliant construction.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX3485ESA+ and SN65HVD3486DR, ST3485EBDR uniquely combines automotive-grade temperature range (-40 to +85 °C), certified ±15 kV IEC ESD, and sub-µA shutdown - making it optimal for industrial edge nodes where reliability, longevity, and power budget co-constrain design.

Availability

ST3485EBDR is available at Aetrix Electronics and suitable for industrial PLC backplanes, smart meter AMI networks, railway signaling nodes, and building automation controllers requiring stable component supply across extended temperature and ESD stress conditions.

Supply support for ST3485EBDR 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, analog ICs, power devices, and sensors for industrial, automotive, and consumer markets.

The ST3485EBDR belongs to ST's RS-485/422 transceiver product line, engineered specifically for noise-immune, multi-drop serial communication in harsh industrial environments with emphasis on ESD resilience, low power, and interoperability.

FAQ

What is the maximum cable length supported at 12 Mbps?

At 12 Mbps, ST3485EBDR supports up to 15 meters of standard 120 Ω twisted-pair cable per the RS-485 specification. Longer distances require reduced data rates: e.g., 1200 meters at 100 kbps. Signal integrity depends on proper termination, stub length control, and cable quality-not solely on transceiver capability.

Does ST3485EBDR require external biasing resistors on the A/B bus lines?

No external biasing resistors are required for basic operation, as the receiver includes internal fail-safe biasing that forces RO high when A/B float. However, for improved noise immunity in unterminated or lightly loaded buses, 560 Ω pull-up on A and pull-down on B (or vice versa) may be added per application note AN4825.

Can ST3485EBDR interface directly with 5 V microcontrollers?

Yes - its logic inputs (DI, DE, RE) accept 5 V TTL/CMOS levels: V_IL ≤ 0.8 V and V_IH ≥ 2.0 V are guaranteed over temperature. The RO output swings rail-to-rail (0 V to VCC), so a level shifter is needed if the MCU reads RO at 5 V logic thresholds.

How does the shutdown mode function, and what triggers it?

Shutdown is activated when DE = low AND RE = high simultaneously for ≥300 ns. This places both driver and receiver in high-impedance states and reduces supply current to ≤1 µA. Inputs must remain stable for at least 300 ns to guarantee entry; shorter pulses (<80 ns) will not trigger shutdown per datasheet timing spec.