Texas Instruments SN74AHC240PW

Overview

SN74AHC240PW from Texas Instruments is an octal 3-state buffer/driver IC designed for bus-oriented applications including memory address drivers, clock distribution, and bidirectional data transmission. It features dual 4-bit channels with independent output-enable (OE) controls, 5.5V-tolerant inputs, 8mA output drive at 5V, and 3.6ns typical propagation delay at 5V supply. It operates across –40°C to +85°C in a 20-pin TSSOP package.

For engineers reviewing the SN74AHC240PW datasheet, SN74AHC240PW pinout, SN74AHC240PW application, or SN74AHC240PW equivalent, this page delivers verified electrical specifications, functional mode behavior, thermal metrics, real-world interface constraints, and validated alternative options for industrial bus buffering and level translation scenarios.

Technical Context

The SN74AHC240PW implements two independent 4-bit non-inverting buffer sections, each controlled by its own active-low output-enable input (1OE and 2OE). When OE is low, data passes from A-inputs to Y-outputs; when high, outputs enter high-impedance state-enabling shared-bus arbitration without external logic.

Its AHC logic family delivers CMOS-level power efficiency with TTL-compatible drive strength: 8mA sink/source at 5V, 4mA at 3.3V, and 50µA at 2V. Input overvoltage tolerance up to 5.5V supports mixed-voltage interfacing, while 116.8°C/W junction-to-ambient thermal resistance reflects its compact TSSOP-20 thermal profile.

Key Specifications

Pinout & Package

TSSOP-20 (PW) package: 6.50mm × 6.4mm body size, 1.2mm max height, lead pitch 0.65mm, RoHS-compliant NiPdAu finish, MSL Level-1.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74AHC240PW, SN74AHCT240PW offers tighter input thresholds for noisy 5V environments but sacrifices 2.5V compatibility, while SN74LVC240APW delivers superior drive and density at 3.3V yet eliminates 5V-tolerant input capability - making SN74AHC240PW the balanced choice for mixed-voltage industrial bus buffering.

Availability

SN74AHC240PW is available at Aetrix Electronics and suitable for industrial PLC backplanes, smartphone power sequencing, and network switch control plane isolation requiring stable component supply and long-term lifecycle support.

Supply support for SN74AHC240PW 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 delivering analog, embedded processing, and connectivity solutions with emphasis on reliability, precision, and energy efficiency.

The SN74AHC240PW belongs to TI's AHC logic family, engineered for high-speed, low-power bus interface applications in industrial, communications, and consumer electronics where voltage translation and robust 3-state control are essential.

FAQ

What is the maximum operating frequency supported by SN74AHC240PW?

The SN74AHC240PW does not specify a hard maximum clock frequency, but its 3.6ns typical propagation delay at 5V and 15pF load supports reliable operation up to approximately 100MHz in well-terminated bus configurations. Real-world frequency limits depend on trace capacitance, fanout, and layout - measured tPLH/tPHL remains ≤6.5ns across –40°C to +85°C at 5V, confirming suitability for high-speed digital control planes.

Does SN74AHC240PW support mixed-voltage operation between 3.3V and 5V domains?

Yes, SN74AHC240PW supports mixed-voltage operation: it can be powered from 3.3V while accepting 5V-tolerant inputs up to 5.5V, enabling direct interfacing between 3.3V microcontrollers and 5V peripherals without external level shifters. Outputs swing rail-to-rail (0V to 3.3V), so downstream 5V receivers require compatible input thresholds or additional conditioning.

How should unused inputs be handled on SN74AHC240PW?

Unused inputs on SN74AHC240PW must be tied to a defined logic level - either VCC or GND - to prevent floating states that cause increased ICC, noise susceptibility, or erratic output behavior. TI explicitly warns against leaving inputs unconnected; pullup/pulldown resistors (typically 10kΩ) are acceptable, but direct connection is preferred for lowest power and best noise immunity.

Is SN74AHC240PW pin-compatible with other TSSOP-20 octal buffers?

SN74AHC240PW shares the same TSSOP-20 footprint and pinout as SN74AHCT240PW and SN74LVC240APW, making them mechanically interchangeable. However, electrical differences - including input threshold voltages, output drive strength, and voltage tolerance - mean direct substitution requires validation of timing, noise margin, and voltage compatibility in the target application.

What thermal considerations apply to SN74AHC240PW in continuous operation?

With a junction-to-ambient thermal resistance (θJA) of 116.8°C/W, SN74AHC240PW dissipates ≤15mW under typical static conditions (ICC ≈ 4µA at 5.5V). Even under worst-case dynamic loading (8mA per output × 8 outputs), total power remains below 100mW - resulting in <12°C junction rise above ambient in still air. No heatsink is required, but ensure adequate copper area and avoid placement near heat sources.