Texas Instruments SN74ACT240PWLE

Overview

SN74ACT240PWLE from Texas Instruments is an octal inverting buffer/driver with 3-state outputs, designed for memory address and bus driving applications. It operates from 4.5 V to 5.5 V, supports TTL-compatible inputs, delivers ≤8.5 ns propagation delay at 5 V, and features separate 1OE/2OE controls for two independent 4-bit sections.

For engineers reviewing the SN74ACT240PWLE datasheet, SN74ACT240PWLE pinout, SN74ACT240PWLE application, or SN74ACT240PWLE equivalent, key selection criteria include 3-state bus isolation capability, 24-mA drive strength per output, TSSOP-20 package compatibility, and guaranteed operation across −40°C to 85°C industrial temperature range.

Technical Context

The SN74ACT240PWLE implements dual 4-bit inverting buffers with independent active-low output-enable (1OE, 2OE) inputs. Each section passes inverted logic from A-inputs to Y-outputs when its OE is low; outputs enter high-impedance state when OE is high. Input voltage tolerance extends to 5.5 V, enabling interfacing with 5-V TTL and mixed-voltage systems.

Its ACT logic family delivers rail-to-rail CMOS output swing with TTL-compatible input thresholds (VIL = 0.8 V, VIH = 2 V), 24-mA sink/source capability, and low quiescent current (ICC ≤ 40 μA). The device requires external pull-up on OE during power sequencing to ensure defined high-Z startup behavior.

Key Specifications

Pinout & Package

TSSOP-20 (PW) package: 6.5 mm × 4.4 mm body, 0.65 mm pitch, 1.2 mm max height, lead-free (RoHS-compliant) finish, MSL Level-1.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74ACT240PWLE, SN74ACT240PWR offers identical performance and form factor with assured supply continuity, while SN74LVC240APW trades 5-V interoperability for lower-voltage efficiency-making the former the direct replacement and the latter a functional alternative only in 3.3-V ecosystems.

Availability

SN74ACT240PWLE is available at Aetrix Electronics and suitable for industrial control, memory subsystems, and legacy bus interface applications requiring stable component supply despite its obsolete status-subject to remaining inventory allocation.

Supply support for SN74ACT240PWLE 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 innovation in industrial and automotive electronics.

The SN74ACT240PWLE belongs to TI's ACT advanced CMOS logic family, engineered for high-speed, low-noise 5-V digital interfacing in industrial computing and real-time control systems.

FAQ

Is SN74ACT240PWLE pin-compatible with other TSSOP-20 octal buffers?

Yes, SN74ACT240PWLE shares the same TSSOP-20 pinout as SN74ACT240PWR and SN74ACT240PW. All three use identical terminal assignments for VCC, GND, A/Y signals, and OE controls-enabling direct PCB footprint reuse. However, SN74LVC240APW has different logic polarity and voltage range, so it is not functionally interchangeable without circuit redesign.

What is the recommended pull-up resistor value for OE pins on SN74ACT240PWLE?

TI recommends a 10-kΩ pull-up resistor from each OE pin (pins 9 and 19) to VCC to ensure reliable high-impedance startup. This value balances current consumption (<0.5 mA total) with noise immunity and rise time, especially under worst-case VCC ramp conditions. Lower values (e.g., 4.7 kΩ) may be used if faster OE assertion is needed in noisy environments.

Can SN74ACT240PWLE interface directly with 3.3-V microcontrollers?

SN74ACT240PWLE accepts 3.3-V logic levels on its inputs (VIH = 2.0 V min), so it can receive signals from 3.3-V MCUs. However, its outputs swing rail-to-rail (0 V to 5 V), so direct connection to 3.3-V-only inputs requires external level-shifting or series resistors to avoid overvoltage damage-unlike true 3.3-V-tolerant devices such as SN74LVC240.

Why is SN74ACT240PWLE marked as obsolete, and is SN74ACT240PWR a valid replacement?

SN74ACT240PWLE is obsolete per TI's 2016 packaging addendum due to end-of-life for that specific tape-and-reel variant. SN74ACT240PWR is the active, functionally identical replacement-same TSSOP-20 package, same AD240 marking, same electrical specs, and same RoHS/Green compliance-making it the authorized drop-in substitute for new and legacy designs.

Does SN74ACT240PWLE require input termination or bus hold circuits?

No, SN74ACT240PWLE does not integrate bus-hold or Schmitt-trigger inputs. TI specifies that all unused inputs must be externally tied to VCC or GND to prevent floating nodes and excessive ICC. For unterminated buses, series resistors (22–33 Ω) at drivers and parallel termination (e.g., 100 Ω to VCC/GND) may be added based on trace length and edge rate-but these are system-level decisions, not IC requirements.