STMicroelectronics ST3485EIYDT

Overview

ST3485EIYDT from STMicroelectronics is an automotive-grade, half-duplex RS-485/RS-422 transceiver with ±15 kV IEC 61000-4-2 ESD protection, guaranteed 12 Mbps data rate, and operation from a single 3.3 V supply (3.0–3.6 V). It integrates one driver and one receiver in an SO8 package, supports up to 64 nodes on the bus, and features thermal shutdown and current limiting for driver overload protection. It is deployed in vehicle body control modules requiring robust differential communication over noisy chassis grounds.

For engineers reviewing the ST3485EIYDT datasheet, ST3485EIYDT pinout, ST3485EIYDT application, or ST3485EIYDT equivalent, key selection criteria include its -40 °C to +125 °C automotive temperature range, industry-standard 75176 pinout compatibility, 1 µA shutdown current, ±7 V to +12 V common-mode input range, and guaranteed high-impedance receiver output during floating-line conditions.

Technical Context

This transceiver implements a half-duplex RS-485/RS-422 physical layer interface with differential driver outputs (A, B) and a differential receiver input pair (A, B), sharing pins per the 75176 standard. The driver delivers ≥1.5 V differential output voltage into 54 Ω (RS-485) and ≥2 V into 100 Ω (RS-422), while the receiver has a ±0.2 V differential threshold with 70 mV hysteresis and guarantees high-Z output when RE is high and DE is low.

Control logic uses active-low RE (receiver enable) and active-high DE (driver enable) to manage direction and power state. When RE = high and DE = low, the device enters shutdown mode drawing ≤1 µA; simultaneous assertion of DE = high and RE = low enables full transmit/receive operation. The receiver maintains a defined output state even with open inputs due to internal fail-safe biasing.

Key Specifications

Pinout & Package

ST3485EIYDT is housed in a surface-mount SO8 (Small Outline 8-pin) package with ECOPACK® environmental compliance, 1.27 mm pitch, and 4.9 mm × 6.0 mm body dimensions.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX13487EESA+ and SN65HVD233DR, ST3485EIYDT provides factory-certified automotive qualification, eliminating program-level requalification risk, while delivering identical electrical performance and pinout - making it the lowest-risk choice for Tier 1 production releases.

Availability

ST3485EIYDT is available at Aetrix Electronics and suitable for automotive body electronics, electric powertrain control, ADAS sensor hubs, and battery management systems requiring stable component supply across extended product lifecycles.

Supply support for ST3485EIYDT 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 automotive ICs for industrial and automotive markets.

The ST3485 series belongs to ST's high-reliability RS-485 transceiver product line, engineered specifically for automotive and industrial environments demanding extended temperature operation, robust ESD immunity, and fail-safe bus behavior.

FAQ

What is the maximum bus length supported by ST3485EIYDT at 12 Mbps?

At the guaranteed 12 Mbps data rate, ST3485EIYDT supports up to 15 m of properly terminated twisted-pair cable (100 Ω characteristic impedance). Longer distances require reducing data rate - e.g., 1200 m is achievable at 100 kbps. Signal integrity depends on stub length, termination quality, and noise environment, not just cable length.

Does ST3485EIYDT require external biasing resistors on the RS-485 bus?

No external biasing resistors are required for basic operation, as the receiver includes internal fail-safe circuitry that forces RO high when A and B are floating or shorted. However, for improved noise immunity in electrically noisy environments (e.g., near inverters), 120 Ω termination across A–B at the bus ends remains mandatory, and optional 560 Ω pull-up/pull-down resistors may be added at the master node.

How does the shutdown mode function, and what signals trigger it?

Shutdown mode is entered when RE is high and DE is low simultaneously - placing both driver outputs (A, B) and receiver output (RO) in high-impedance state while reducing supply current to ≤1 µA. This state is guaranteed after ≥300 ns of valid input timing; transitions shorter than 80 ns will not activate shutdown. DI state is irrelevant during shutdown.

Can ST3485EIYDT interface directly with a 5 V microcontroller GPIO?

Yes - the logic control pins (DE, RE, DI) are 5 V tolerant, accepting input voltages from 0 V to 7 V regardless of VCC level. No level-shifting circuitry is needed when connecting to 5 V MCUs, though the transceiver itself must be powered from 3.3 V. Output RO is CMOS-compatible and swings rail-to-rail (0 V to VCC), so a 3.3 V MCU reads it correctly.