Texas Instruments SN74HCT240DWG4

Overview

SN74HCT240DWG4 from Texas Instruments is an octal inverting buffer/line driver with 3-state outputs, designed for memory address and bus driving in industrial control and instrumentation systems. It operates at 4.5–5.5 V, delivers ±6 mA output drive, exhibits 12 ns typical propagation delay, and draws ≤80 μA supply current. Its dual 4-bit structure with independent OE inputs enables selective bus isolation.

For engineers reviewing the SN74HCT240DWG4 datasheet, SN74HCT240DWG4 pinout, SN74HCT240DWG4 application, or SN74HCT240DWG4 equivalent, key selection criteria include 3-state bus compatibility, TTL-input voltage thresholds (VIH = 2 V, VIL = 0.8 V), high-current drive capability (±6 mA), low ICC, and SOIC-20 package thermal performance (RθJA = 109.1 °C/W).

Technical Context

The SN74HCT240DWG4 implements two independent 4-bit inverting buffers, each controlled by a dedicated output-enable (OE) input. When OE is low, inverted data passes from A inputs to Y outputs; when OE is high, all eight outputs enter high-impedance state-enabling bidirectional bus sharing without contention.

It uses HCMOS-compatible circuitry with TTL-level input thresholds and CMOS-level output swing, ensuring interoperability with legacy LSTTL loads while maintaining low power consumption. The device supports CL = 50 pF and CL = 150 pF load conditions, with tpd ranging from 12 ns (5.5 V, 50 pF) to 56 ns (4.5 V, 150 pF).

Key Specifications

Pinout & Package

SN74HCT240DWG4 is housed in a 20-pin SOIC (DW) package measuring 12.80 mm × 10.3 mm (body: 12.80 mm × 7.50 mm), with standard 1.27 mm pitch and gull-wing leads. Thermal resistance is RθJA = 109.1 °C/W, supporting moderate power dissipation in compact layouts.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HCT240DWR and 74HCT240N, the SN74HCT240DWG4 offers identical core functionality in a tube-packaged SOIC-20 variant-ideal for low-volume validation, lab testing, or mixed-technology boards requiring both surface-mount and through-hole components.

Availability

SN74HCT240DWG4 is available at Aetrix Electronics and suitable for industrial control, instrumentation data acquisition, and test equipment design requiring stable component supply and long-term manufacturability.

Supply support for SN74HCT240DWG4 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 for industrial, automotive, and communications markets.

The SN74HCT240DWG4 belongs to TI's 74HCT logic family, engineered for TTL-compatible interfacing with CMOS power efficiency-targeting memory expansion, bus buffering, and industrial control system interconnect.

FAQ

What is the logic function of the SN74HCT240DWG4?

The SN74HCT240DWG4 is an octal inverting buffer with 3-state outputs, organized as two independent 4-bit sections. Each section inverts input signals (A → Y) when its output-enable (OE) pin is low; when OE is high, outputs go high-impedance. This enables bus sharing and directional control in memory and peripheral interfaces. The SN74HCT240DWG4 maintains strict TTL-compatible input thresholds and CMOS output drive characteristics.

Does the SN74HCT240DWG4 support 3.3 V operation?

No, the SN74HCT240DWG4 is specified only for 4.5 V to 5.5 V supply operation. Its TTL-compatible inputs require VIH ≥ 2.0 V and VIL ≤ 0.8 V, and its output drive strength (±6 mA) and propagation delay (12 ns typical) are characterized exclusively within the 5 V range. Using it at 3.3 V may result in undefined logic states, excessive delay, or failure to meet output voltage specifications. For 3.3 V systems, consider the SN74LVC240 or similar LVC-family devices.

What is the maximum capacitive load the SN74HCT240DWG4 can drive reliably?

The SN74HCT240DWG4 is characterized for CL = 50 pF and CL = 150 pF loads. At 5.5 V supply, tpd increases from 12 ns (50 pF) to 56 ns (150 pF); ten and tdis similarly rise. TI specifies guaranteed switching performance up to 150 pF. Driving >150 pF risks timing violations, increased rise/fall times, and potential signal integrity issues-external series termination or buffer staging is recommended beyond this limit. The SN74HCT240DWG4's Cpd = 40 pF further confirms its suitability for moderate-speed, medium-load applications.

How should unused inputs be handled on the SN74HCT240DWG4?

All unused inputs on the SN74HCT240DWG4 must be tied to a defined logic level-either VCC or GND-to prevent floating nodes that cause increased ICC, erratic output behavior, or ESD susceptibility. TI explicitly states that unused inputs must not be left unconnected. For example, if only four of eight buffers are used, the remaining four A inputs should be pulled high (to VCC) or low (to GND) using appropriate resistors or direct connections. This requirement applies equally to OE pins: unused OE inputs must also be held low (to enable) or high (to disable) depending on system intent. The SN74HCT240DWG4 does not include internal pull-ups or pull-downs.

Is the SN74HCT240DWG4 RoHS compliant?

Yes, the SN74HCT240DWG4 is RoHS compliant. Per TI's Packaging Information, the DWG4 variant (SOIC-20, tube packaging) carries NIPDAU lead finish and meets RoHS Directive 2011/65/EU requirements. It is rated MSL Level-1 (unlimited floor life at ≤30 °C/60% RH) and qualified for peak reflow of 260 °C. The "G4" suffix denotes green (halogen-free) packaging per TI's environmental standards. All active SOIC variants-including SN74HCT240DWR and SN74HCT240DWRE4-share this compliance status. The SN74HCT240DWG4 is suitable for environmentally regulated industrial and commercial end equipment.