Texas Instruments SN74BCT245NSR

Overview

SN74BCT245NSR from Texas Instruments is an octal bus transceiver with 3-state outputs, designed for asynchronous bidirectional data transfer between A and B buses in 5-V TTL systems. It features direction control (DIR), output enable (OE), ±128 mA sink capability on B-port outputs, 7 ns max propagation delay at 5 V/50 pF, and operates from 0°C to 70°C. It is commonly used in memory address register buffering and legacy bus isolation applications.

For engineers reviewing the SN74BCT245NSR datasheet, SN74BCT245NSR pinout, SN74BCT245NSR application, or SN74BCT245NSR equivalent, key selection considerations include its 20-pin SOP-NS package, 3-state bus-driving capability, TTL-compatible input thresholds, and compatibility with SN74BCT244/SN74BCT240 families in system-level bus interface designs.

Technical Context

This device implements dual 8-bit bidirectional bus transceivers with independent DIR and OE controls. Data flows from A to B when DIR = HIGH and OE = LOW; from B to A when DIR = LOW and OE = LOW. When OE = HIGH, both A and B ports enter high-impedance state, isolating the buses.

It uses bipolar TTL circuitry with BCT (Bipolar CMOS-TTL) process, delivering higher drive strength than standard 74LS while maintaining TTL logic thresholds. The B-port outputs support up to 64 mA sink current per pin, enabling direct connection to TTL loads without external pull-ups.

Key Specifications

Pinout & Package

SOP-NS package: 20-pin small-outline plastic package, 0.635 mm pitch, 7.5 mm × 13.0 mm body size, 2.0 mm max height, RoHS-compliant NiPdAu lead finish, MSL Level-1 (260°C peak reflow).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar octal bus transceiver applications.

Compared with SN74BCT245NSR, SN74BCT244NSR removes bidirectionality but simplifies control logic, while SN74LVTH245PWRE4 trades 5-V drive strength for 3.3-V compatibility and lower power - making each optimal for distinct voltage-domain and control-architecture requirements.

Availability

SN74BCT245NSR is available at Aetrix Electronics and suitable for memory address buffering, legacy bus isolation, microcontroller parallel interface, and industrial I/O module expansion requiring stable component supply across long-lifecycle embedded programs.

Supply support for SN74BCT245NSR 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

Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and logic solutions, with decades of experience in industrial, automotive, and communications infrastructure markets.

The SN74BCT245NSR belongs to TI's legacy BCT logic family, engineered for high-noise-immunity, high-drive 5-V TTL bus interfacing in mission-critical industrial control and test equipment.

FAQ

What is the maximum operating temperature range for the SN74BCT245NSR?

The SN74BCT245NSR is rated for operation from 0°C to 70°C ambient temperature. This commercial-grade specification aligns with its SOP-NS packaging and intended use in non-military industrial and computing applications. The SN54BCT245 variant extends to –55°C to 125°C for military environments, but SN74BCT245NSR does not support that extended range.

Can the SN74BCT245NSR be used with 3.3-V logic inputs?

No - the SN74BCT245NSR requires TTL-compatible input thresholds: VIH ≥ 2.0 V and VIL ≤ 0.8 V at VCC = 5 V. Driving it directly from 3.3-V CMOS outputs risks marginal high-level recognition. For 3.3-V systems, TI recommends SN74LVTH245PWRE4 or level-shifter buffers before SN74BCT245NSR inputs.

What is the recommended PCB layout practice for SN74BCT245NSR power integrity?

Place a 0.1-µF ceramic decoupling capacitor between VCC (pin 11) and GND (pin 10) as close as possible - ideally within 1 cm and with short, wide traces. Avoid shared vias; use dedicated GND plane under the device. Route DIR and OE control lines away from high-speed data traces to prevent coupling-induced glitches on SN74BCT245NSR control inputs.

Does the SN74BCT245NSR support hot-swap or live-insertion?

The SN74BCT245NSR itself has no built-in hot-swap protection, but its 3-state OE control enables safe live insertion when coordinated with system firmware. Asserting OE = HIGH before physical insertion isolates the A and B buses; after mechanical connection, OE can be deasserted. External series resistors (22–47 Ω) on B-port lines are recommended to limit inrush current.

How does the SN74BCT245NSR differ from the SN74BCT245DBR?

Both share identical logic function, electrical specs, and pinout, but SN74BCT245NSR uses SOP-NS (narrow-body SOIC) packaging (7.5 mm × 13.0 mm), while SN74BCT245DBR uses SSOP-DB (shrink small-outline) packaging (5.3 mm × 7.2 mm). NS offers better thermal resistance (θJA = 60°C/W vs. 70°C/W for DB) and is preferred for thermally constrained layouts, though DB saves board area.