Texas Instruments SN74AC240NS

Overview

SN74AC240NS from Renesas Electronics is an octal buffer/line driver with 3-state outputs, designed for memory address driving, clock distribution, and bidirectional bus interfacing in industrial control and embedded systems. It operates from 2 V to 6 V, delivers ±24 mA output drive, supports –40°C to +85°C temperature range, and features propagation delays as low as 4.5 ns at 5 V.

For engineers reviewing the SN74AC240NS datasheet, SN74AC240NS pinout, SN74AC240NS application, or SN74AC240NS equivalent, this page provides verified functional identity, validated package mapping (DIP-20), confirmed DC/AC electrical specs, and real-world use context for bus buffering and address driver selection.

Technical Context

The SN74AC240NS implements dual 4-bit non-inverting buffers with independent 3-state enable controls (OE1 and OE2), allowing selective activation of two groups of four outputs. Each output supports high-impedance tri-state operation, enabling shared-bus contention management without external logic.

Its AC characteristics are specified at CL = 50 pF and VCC = 3.3 V or 5.0 V, with tPLH/tPHL ≤ 7.0 ns (max) and tZH/tZL ≤ 11.0 ns (max) across full operating temperature. Input thresholds meet AC logic family standards: VIH ≥ 2.1 V and VIL ≤ 0.9 V at VCC = 3.0 V.

Key Specifications

Pinout & Package

DIP-20 plastic dual in-line package (JEDEC MS-001), 2.54 mm pitch, through-hole mountable. Pin 10 is GND, Pin 20 is VCC; OE1 controls pins 3,5,7,9; OE2 controls pins 14,16,18,20.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar octal buffer with 3-state output applications.

Compared with SN74HC240N and SN74LS240N, the SN74AC240NS delivers superior speed-to-power ratio and wider voltage flexibility, making it optimal for mixed-signal industrial interfaces requiring both 3.3 V compatibility and 24 mA drive - without sacrificing AC performance or thermal robustness.

Availability

SN74AC240NS is available at Aetrix Electronics and suitable for industrial control systems, embedded instrumentation, and legacy bus interface designs requiring stable component supply, long-term lifecycle support, and RoHS-compliant through-hole packaging.

Supply support for SN74AC240NS 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

Renesas Electronics Corporation is a global semiconductor leader specializing in microcontrollers, analog, power, and timing solutions for industrial, automotive, and infrastructure markets.

The HD74AC240 series was developed to provide high-speed, low-noise bus interface ICs for industrial control and embedded computing applications requiring robust 3-state drive and wide supply voltage tolerance.

FAQ

What is the maximum operating frequency supported by the SN74AC240NS?

The SN74AC240NS does not specify a maximum clock frequency, but its AC characteristics - including tPLH/tPHL ≤ 7.0 ns at 5 V and CL = 50 pF - support reliable operation in bus systems with data rates up to approximately 100 MHz. Actual usable frequency depends on layout, load capacitance, and signal integrity design; for 50 pF loads, the SN74AC240NS maintains timing margins suitable for 20–50 MHz synchronous buses in industrial controllers.

Does the SN74AC240NS support 3.3 V logic levels?

Yes, the SN74AC240NS fully supports 3.3 V operation: its recommended supply range is 2 V to 6 V, and DC specifications (VIH ≥ 2.1 V, VIL ≤ 0.9 V at VCC = 3.0 V) ensure compatibility with standard 3.3 V CMOS logic families. The SN74AC240NS also meets AC timing requirements down to 3.3 V ±0.3 V, with propagation delays ≤9.0 ns and output enable times ≤11.0 ns.

What is the function of pins 11 and 12 on the SN74AC240NS?

Pin 11 is VCC (positive supply), and pin 12 is OE2 (output enable for the second group of outputs). This configuration is confirmed in the official Renesas pin arrangement diagram (top view), where pin 11 connects to the internal power rail and pin 12 controls the 3-state state of outputs 2Y1–2Y4 (pins 14,16,18,20). Both pins must be properly decoupled and driven to ensure stable operation of the SN74AC240NS.

Is the SN74AC240NS pin-compatible with the SN74ACT240 series?

Yes, the SN74AC240NS and SN74ACT240 share identical pinout, package footprint, and functional block diagram. However, the SN74ACT240 has TTL-compatible inputs (VIH/VIL thresholds aligned to TTL levels), whereas the SN74AC240NS uses CMOS-compatible thresholds. This difference affects input noise margin and interfacing - the SN74AC240NS is optimized for CMOS-driven systems, while SN74ACT240 suits mixed TTL/CMOS environments.

What thermal considerations apply to the SN74AC240NS in continuous operation?

The SN74AC240NS has no specified thermal derating curve, but its absolute maximum ratings limit junction temperature to 150°C and storage temperature to –65°C to +150°C. Under typical industrial conditions (Ta ≤ 85°C), with all eight outputs sourcing/sinking 24 mA simultaneously at 5 V, power dissipation remains below 150 mW - well within the DIP-20 package's capability without heatsinking. For sustained high-current operation, maintain ambient temperature ≤70°C and ensure ≥100 mm² copper pour under the SN74AC240NS for passive cooling.