Texas Instruments SN74AHCT240DW

Overview

SN74AHCT240DW from Texas Instruments is an octal inverting buffer/driver with tri-state outputs, designed for bus-oriented receivers and transmitters in 5-V systems. It features TTL-compatible inputs (VIH = 2 V, VIL = 0.8 V), ±8-mA output drive, 9.5-ns max propagation delay at 5 V/50 pF, and operates from –40°C to 125°C. Used in memory-address driver and clock distribution circuits where controlled bus isolation is required.

For engineers reviewing the SN74AHCT240DW datasheet, SN74AHCT240DW pinout, SN74AHCT240DW application, or SN74AHCT240DW equivalent, this page delivers verified electrical specs, SOIC-20 package details, functional mode behavior, real-world use cases in industrial and consumer electronics, and validated alternative parts for design continuity.

Technical Context

The SN74AHCT240DW implements two independent 4-bit inverting buffer sections, each with dedicated output-enable (OE) control. Each section passes inverted logic from A-inputs to Y-outputs when OE is low; outputs enter high-impedance state when OE is high. Input thresholds are optimized for TTL compatibility while operating from a single 4.5–5.5-V supply.

It uses advanced CMOS technology with slow edge rates to minimize output ringing and overshoot-critical in lightly loaded bus environments. The device supports voltage translation from 3.3-V logic domains to 5-V buses, with inputs tolerant up to 5.5 V regardless of VCC level.

Key Specifications

Pinout & Package

SN74AHCT240DW is housed in a 20-pin SOIC (DW) package measuring 12.80 mm × 10.3 mm (body: 12.8 mm × 7.5 mm), with standard 1.27-mm pitch and gull-wing leads suitable for reflow soldering.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar octal inverting buffer applications.

Compared with SN74AHCT240DWR and SN74LVC240APWR, the SN74AHCT240DW offers unique TTL-input compatibility and 5-V operation in a legacy SOIC tube format-making it optimal for repair, legacy system refresh, and designs requiring guaranteed 5-V interoperability without redesign.

Availability

SN74AHCT240DW is available at Aetrix Electronics and suitable for industrial control, power infrastructure monitoring, and consumer display timing applications requiring stable component supply and long-lifecycle support.

Supply support for SN74AHCT240DW 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 90 years of innovation in industrial, automotive, and communications markets.

The SN74AHCT240DW belongs to TI's 74AHCT logic family-designed for robust 5-V TTL-compatible interfacing in mission-critical industrial and infrastructure systems where reliability and backward compatibility are essential.

FAQ

What is the function of the OE pins on the SN74AHCT240DW?

The SN74AHCT240DW has two active-low output-enable pins: 1OE (Pin 1) controls the first four inverting buffers (1A1–1A4 → 1Y1–1Y4), and 2OE (Pin 19) controls the second group (2A1–2A4 → 2Y1–2Y4). When either OE is high, its associated Y outputs enter high-impedance state; when low, inverted data passes through. This enables independent bus segment control without external logic.

Does the SN74AHCT240DW support 3.3-V input logic levels?

Yes-the SN74AHCT240DW accepts 3.3-V logic inputs reliably because its VIH threshold is only 2 V and VIL is 0.8 V, well within 3.3-V CMOS logic margins. Inputs are also overvoltage tolerant up to 5.5 V, allowing safe interfacing with mixed-voltage systems without clamping diodes or resistors.

What is the maximum capacitive load the SN74AHCT240DW can drive?

The SN74AHCT240DW is characterized for CL = 15 pF and CL = 50 pF loads in its switching specifications. While not explicitly rated beyond 50 pF, its ±8-mA drive strength and slow edge rates allow stable operation into typical PCB traces and small fanouts (e.g., ≤5 TTL loads or ≤10 cm of 50-Ω trace). For heavier loads, consult TI's application note SCBA005.

Is the SN74AHCT240DW pin-compatible with other 74-series octal buffers?

Yes-the SN74AHCT240DW shares identical pinout and function with industry-standard 74240-compatible devices including SN74LS240, SN74ALS240, and SN74F240. All use the same SOIC-20 footprint, signal mapping, and dual-OE architecture, enabling direct replacement in existing layouts where voltage and speed requirements align.

Why does the SN74AHCT240DW have two separate OE inputs instead of one?

The dual OE architecture in the SN74AHCT240DW allows independent control of two 4-bit data paths-enabling simultaneous but segregated bus operations. For example, one group can drive address lines while the other handles control signals, reducing contention risk and simplifying timing in memory-mapped peripherals. This partitioning improves system-level fault isolation and flexibility.