Texas Instruments SN74S240DWG4

Overview

SN74S240DWG4 from Texas Instruments is an octal inverting buffer/line driver with 3-state outputs, designed for memory address and bus driving applications. It features dual 4-bit channels with independent active-low output-enable (1G, 2G/2G) control, 7 ns typical propagation delay at 5 V, ±64 mA output drive capability, and PNP input structure reducing DC loading on buses.

For engineers reviewing the SN74S240DWG4 datasheet, SN74S240DWG4 pinout, SN74S240DWG4 application, or SN74S240DWG4 equivalent, key selection considerations include its 3-state bus interface capability, high-current drive for terminated lines down to 133 Ω, hysteresis-enhanced noise immunity, compatibility with 3.3-V/5-V mixed logic systems, and SOIC-20 package suitability for space-constrained industrial PCBs.

Technical Context

The SN74S240DWG4 implements two independent 4-bit inverting buffer sections, each with separate active-low output-enable inputs (1G and 2G/2G). Its Schottky transistor logic (S-TTL) architecture delivers fast switching (tPLH/tPHL ≤7 ns) while maintaining robust DC characteristics including 0.55 V max VOL at 64 mA sink current and 2.7 V min VOH at –1 mA source current.

Input hysteresis (0.2–0.4 V) improves noise margins on shared bus lines, and PNP input structure reduces DC loading-critical for high-fan-out memory address buffering. The device operates across 4.75–5.25 V supply range with specified functionality over 0°C to 70°C ambient temperature.

Key Specifications

Pinout & Package

SN74S240DWG4 is housed in a 20-pin SOIC (DW) package measuring 12.80 mm × 7.50 mm, optimized for surface-mount assembly and thermal dissipation in dense PCB layouts.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74LS240DW and SN74ALS240N, SN74S240DWG4 provides superior drive strength and speed for demanding bus applications but at higher power consumption-making it optimal for terminated-line driving where signal integrity outweighs quiescent current concerns.

Availability

SN74S240DWG4 is available at Aetrix Electronics and suitable for memory address buffering, bus line driving, LED display multiplexing, and telecom signal re-timing requiring stable component supply across industrial production cycles.

Supply support for SN74S240DWG4 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 company specializing in analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.

SN74S240DWG4 belongs to TI's legacy S-TTL logic family, engineered specifically for high-speed, high-drive bus interface and memory address buffering in industrial control and telecom infrastructure systems.

FAQ

What is the maximum output sink current specification for SN74S240DWG4?

The SN74S240DWG4 is rated for 64 mA maximum low-level output current (IOL) per channel under recommended operating conditions. This value is confirmed in Section 6.3 (Recommended Operating Conditions) and Section 6.6 (Electrical Characteristics – SNx4S24x) of the official TI datasheet SDLS144D. The high sink capability enables direct driving of terminated transmission lines down to 133 Ω without external buffers, making SN74S240DWG4 suitable for demanding memory bus and backplane applications.

Does SN74S240DWG4 support mixed-voltage logic interfacing?

Yes, SN74S240DWG4 supports mixed-voltage logic interfacing. Its inputs tolerate voltages as low as 2 V for VIH recognition, allowing reliable operation with 3.3-V CMOS or LVTTL outputs while powered from a 5-V supply. This capability is explicitly stated in the "Features" section and verified in Section 6.3 (Recommended Operating Conditions) of the TI datasheet SDLS144D. The design enables seamless integration into heterogeneous systems containing both 3.3-V and 5-V logic domains without level-shifting components.

What is the typical propagation delay of SN74S240DWG4 at 5 V?

The typical propagation delay (tPLH and tPHL) of SN74S240DWG4 is 7 ns when operated at VCC = 5 V, TA = 25°C, with RL = 90 Ω and CL = 50 pF, as specified in Section 6.8 (Switching Characteristics – SNx4S24x) of the TI datasheet SDLS144D. This value reflects the device's Schottky transistor logic (S-TTL) architecture, which delivers faster switching than standard LS-TTL variants like SN74LS240. The 7 ns figure is critical for timing-critical memory address and bus driving applications.

How does the hysteresis feature benefit SN74S240DWG4 in noisy environments?

The SN74S240DWG4 incorporates input hysteresis of 0.2–0.4 V (VT+ − VT−), as documented in Section 6.6 of the TI datasheet SDLS144D. This hysteresis increases noise immunity on shared bus lines by creating distinct voltage thresholds for rising and falling input transitions-preventing false triggering due to ringing, crosstalk, or ground bounce. In practice, this allows SN74S240DWG4 to maintain reliable operation on long PCB traces or backplanes in industrial settings where EMI is prevalent, without requiring additional filtering components.

What package type is used for SN74S240DWG4 and what are its key mechanical dimensions?

SN74S240DWG4 uses a 20-pin SOIC (DW) package with nominal body dimensions of 12.80 mm × 7.50 mm, as confirmed in the "Device Information" table of the TI datasheet SDLS144D. This surface-mount package supports automated assembly and provides adequate thermal performance for commercial-temperature applications. The DW suffix denotes the SOIC variant, and the G4 suffix indicates TI's green (RoHS-compliant) packaging standard. No lead finish or moisture sensitivity level deviations are noted beyond standard JEDEC SOIC specifications.