Texas Instruments SN74ALS245ANS

Overview

SN74ALS245ANS from Texas Instruments is an octal bus transceiver with 3-state outputs, designed for asynchronous bidirectional data transfer between A and B buses in TTL-compatible systems. It operates from 4.5 V to 5.5 V, delivers a maximum propagation delay of 5.5 ns at 5 V, and features pnp input circuitry to reduce DC loading. It is commonly used in legacy industrial control backplanes and memory-mapped I/O expansion interfaces.

For engineers reviewing the SN74ALS245ANS datasheet, SN74ALS245ANS pinout, SN74ALS245ANS application, or SN74ALS245ANS equivalent, key selection considerations include its 20-pin SOP-NS package, 3-state output control via DIR/OE inputs, guaranteed 12 mA low-level output drive (24 mA typical), and compatibility with ALS logic family timing and voltage thresholds.

Technical Context

This device implements dual-directional 8-bit data flow controlled by separate DIR (direction) and OE (output enable) inputs. The DIR signal determines whether data passes from A-to-B (DIR = HIGH) or B-to-A (DIR = LOW), while OE independently disables all outputs into high-impedance state regardless of DIR state.

Its internal pnp input structure lowers input current draw compared to standard TTL, reducing bus loading. Output stages are designed for direct connection to terminated or unterminated bus lines, with VOL ≤ 0.4 V at IOL = 12 mA and VOH ≥ 2.4 V at IOH = –12 mA under recommended operating conditions.

Key Specifications

Pinout & Package

SOP-NS (Small Outline Package, narrow body) with 20 leads, 0.65 mm pitch, 7.5 mm × 5.0 mm body size, and 2.0 mm max height per TI DB0020A specification.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74ALS245AN and SN74AS245NSR, the SN74ALS245ANS offers surface-mount SOP-NS packaging for modern automated assembly, balanced speed/power trade-off (5.5 ns / 38 mA disabled), and proven reliability in commercial-temperature industrial bus interfaces.

Availability

SN74ALS245ANS is available at Aetrix Electronics and suitable for industrial backplane interfaces, memory-mapped I/O expansion, legacy system bus arbitration, and TTL-compatible logic subsystems requiring stable component supply across long product lifecycles.

Supply support for SN74ALS245ANS 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 over 50 years of industrial-grade component heritage.

The SN74ALS245ANS belongs to TI's legacy 74ALS logic family, engineered specifically for high-reliability, low-loading, medium-speed bidirectional bus interfacing in commercial-temperature industrial and computing systems.

FAQ

What is the maximum operating temperature range for the SN74ALS245ANS?

The SN74ALS245ANS is rated for operation from 0°C to 70°C, meeting commercial-grade specifications. This range supports deployment in office automation equipment, industrial controllers, and embedded computing platforms where ambient temperatures remain within standard environmental limits. The device's thermal resistance (θJA = 60°C/W for NS package) ensures safe junction temperatures under typical load conditions at 70°C ambient.

Does the SN74ALS245ANS support true bidirectional data flow without external logic?

Yes, the SN74ALS245ANS supports true bidirectional data flow using only its DIR and OE inputs-no external gates or clocks are needed. When OE is LOW, asserting DIR HIGH routes data from A to B; asserting DIR LOW routes data from B to A. This native dual-direction capability simplifies PCB layout and reduces component count in bus interface designs.

What is the output drive strength of the SN74ALS245ANS at 5 V supply?

At VCC = 5 V, the SN74ALS245ANS guarantees a minimum low-level output current (IOL) of 12 mA and a typical value of 24 mA. Its high-level output current (IOH) is specified at –12 mA minimum. These values ensure robust driving of standard TTL loads (up to 10 units) or 50 Ω transmission lines, maintaining VOL ≤ 0.4 V and VOH ≥ 2.4 V under full load.

Is the SN74ALS245ANS pin-compatible with the SN74LS245?

Yes, the SN74ALS245ANS is functionally and pin-compatible with the SN74LS245 in the same SOP-NS package, sharing identical pin assignments, logic behavior, and DC characteristics. However, it improves propagation delay (5.5 ns vs. 14 ns typical) and reduces input current (0.1 mA vs. 1.6 mA), making it a direct performance upgrade for existing LS-based designs.

What package type does the SN74ALS245ANS use, and what are its key mechanical dimensions?

The SN74ALS245ANS uses the SOP-NS (Small Outline Package, narrow body) with 20 leads. Per TI DB0020A, it measures 7.5 mm × 5.0 mm with 0.65 mm lead pitch and a maximum height of 2.0 mm. Its land pattern requires 0.45 mm pad width, 1.85 mm pad length, and 0.65 mm center-to-center spacing-fully compatible with IPC-7351 SOIC-N standards.