STMicroelectronics ST26C31BN

Overview

ST26C31BN from STMicroelectronics is a CMOS quad 3-state differential line driver compliant with EIA RS-422, operating from a single 5 V supply, featuring 6 ns typical propagation delay, 0.5 ns typical output skew, and TTL-input compatibility for balanced digital data transmission in industrial serial interfaces.

For engineers reviewing the ST26C31BN datasheet, ST26C31BN pinout, ST26C31BN application, or ST26C31BN equivalent, key selection criteria include RS-422 differential drive capability, 3-state bus interface support, low quiescent current (200–500 µA), and DIP-16 package suitability for legacy PCB layouts and test fixtures.

Technical Context

The ST26C31BN implements four independent differential drivers with shared enable logic per pair (pins 4 & 12), each translating TTL/CMOS inputs into RS-422-compliant differential outputs (AOUT/AOUT, BOUT/BOUT, etc.). All outputs feature diode-based ESD protection to V_CC and ground.

It operates within 4.5–5.5 V supply range and supports full -40°C to +85°C industrial temperature operation. When V_CC = 0 V, outputs remain high-impedance and non-loading - critical for hot-swap and power-gated system designs.

Key Specifications

Pinout & Package

ST26C31BN is supplied in a 16-pin plastic dual in-line package (DIP-16) with 0.3-inch body width and through-hole mounting. Pin 1 is marked by a notch or dot; pin numbering follows standard counter-clockwise layout.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar differential line driver applications.

Compared with SN75174N and MAX488CPA+, ST26C31BN uniquely combines 3-state control per channel pair, zero-V_CC output isolation, and ±150 mA drive - making it optimal for industrial backplanes requiring hot-swap readiness and multi-drop bus arbitration.

Availability

ST26C31BN is available at Aetrix Electronics and suitable for industrial PLC backplanes, factory automation serial links, legacy test equipment interfaces, and avionics data concentrators requiring stable component supply and long-term DIP-16 availability.

Supply support for ST26C31BN 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, digital, and mixed-signal ICs for automotive, industrial, and consumer markets.

The ST26C31B series belongs to ST's legacy industrial interface portfolio, engineered specifically for robust RS-422 physical layer implementation in harsh electromagnetic environments with strict power and thermal constraints.

FAQ

What is the maximum data rate supported by ST26C31BN?

ST26C31BN supports reliable operation up to 30 Mbps under typical conditions (5 V supply, 25°C, 100 Ω load), based on its 6 ns propagation delay and 10 ns differential rise/fall times. Actual achievable rate depends on trace length, termination, and noise; for 100 m cables, 1–5 Mbps is recommended per EIA-422 guidelines.

Can ST26C31BN drive unterminated RS-422 lines?

No - ST26C31BN requires proper 100 Ω differential termination at the receiver end to maintain signal integrity and prevent reflections. Driving unterminated lines causes overshoot, ringing, and potential receiver misreads due to lack of impedance matching, especially beyond 10 m cable length.

Is ST26C31BN compatible with RS-485 networks?

ST26C31BN is an RS-422 driver only and lacks RS-485 half-duplex bus arbitration features like driver enable/disable overlap control or fail-safe biasing. It can transmit on RS-485 physical layers if used in point-to-point mode with external direction control, but does not meet RS-485 electrical or functional standards.

Does ST26C31BN require external pull-up or pull-down resistors on inputs?

No - ST26C31BN inputs have no internal biasing and exhibit ±1 µA leakage, so external resistors are required only if floating inputs must be held to defined logic states. For TTL-compatible operation, inputs driven directly from microcontroller GPIOs need no external biasing; unused inputs should be tied to V_CC or GND.