Texas Instruments SN74LVC240ANS

Overview

SN74LVC240A from Texas Instruments is an octal non-inverting buffer/driver with dual 3-state output banks, operating from 1.65V to 3.6V supply, supporting 5.5V-tolerant inputs, with 6.5ns max propagation delay at 3.3V, and Ioff for live insertion-used in bus buffering, signal redriving, and controller reset hold applications.

For engineers reviewing the SN74LVC240A datasheet, SN74LVC240A pinout, SN74LVC240A application, or SN74LVC240A equivalent, key selection criteria include dual-bank 3-state control, mixed-mode voltage operation (5V input/3.3V VCC), ground bounce & undershoot performance, thermal metrics per package variant, and Ioff-enabled partial-power-down capability.

Technical Context

The SN74LVC240A implements two independent 4-channel banks (Bank 1: 1A1–1A4 → 1Y1–1Y4; Bank 2: 2A1–2A4 → 2Y1–2Y4), each controlled by a dedicated active-low output enable (1OE, 2OE). Its CMOS architecture delivers balanced sourcing/sinking drive (±24mA at 3V) and supports true 3-state isolation with leakage <±20μA in disabled mode.

It features overvoltage-tolerant inputs (up to 5.5V regardless of VCC), Ioff protection enabling safe operation during power sequencing, and Schmitt-trigger–free standard CMOS inputs requiring fast transitions (<6 ns/V) to prevent oscillation. The device does not incorporate internal hysteresis or level-shifting circuitry-voltage translation relies on external biasing or system-level interface design.

Key Specifications

Pinout & Package

SN74LVC240A is available in multiple surface-mount packages including TSSOP-20 (PW), SOIC-20 (DW), SSOP-20 (DB), SOP-20 (NS), VSSOP-20 (DGS), VQFN-20 (RKS), and TVSOP-20 (DGV). Body sizes range from 4.5mm × 2.5mm (RKS) to 12.8mm × 7.5mm (DW); all variants are 20-pin, with identical pin function mapping across packages except for thermal pad presence in RKS.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74LVC240A, SN74LVC244A sacrifices bank-level granularity for pin compatibility, while 74LVC8T245 adds directionality and dual-supply flexibility at the cost of increased complexity and reduced drive strength per channel.

Availability

SN74LVC240A is available at Aetrix Electronics and suitable for bus buffering, signal redriving, and controller reset hold applications requiring stable component supply across automotive, industrial control, and embedded computing programs.

Supply support for SN74LVC240A 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 decades of expertise in high-reliability interface and power management ICs.

The SN74LVC240A belongs to TI's LVC (Low-Voltage CMOS) logic family, designed specifically for low-voltage, high-speed digital interfacing in space-constrained, thermally demanding applications where mixed-voltage compatibility and robust bus control are essential.

FAQ

What is the maximum input voltage the SN74LVC240A can tolerate?

The SN74LVC240A accepts input voltages up to 5.5V regardless of VCC level-enabling direct connection to 5V sources while operating from 1.65V to 3.6V supplies. This overvoltage tolerance is specified in the Absolute Maximum Ratings table and verified across temperature ranges. The SN74LVC240A does not require external clamping diodes or level shifters for 5V-to-3.3V interfacing, simplifying system design and reducing BOM count.

How does the SN74LVC240A handle power sequencing during hot-swap events?

The SN74LVC240A incorporates Ioff circuitry that disables all outputs when VCC = 0V, limiting leakage current to ±20μA and preventing back-drive damage to upstream or downstream components. This feature allows safe live insertion into partially powered systems-critical in modular backplanes or field-replaceable units. The SN74LVC240A maintains this protection across –40°C to 125°C, ensuring reliability in industrial and automotive environments.

Can the SN74LVC240A drive a 50Ω transmission line directly?

Yes-the SN74LVC240A delivers ±24mA output drive at 3V, sufficient to source/sink current into a 50Ω load while maintaining VOL < 0.55V and VOH > 2.2V. When combined with series damping resistors (e.g., 22Ω–50Ω near the output), it achieves clean signal integrity on traces up to 12 cm. The SN74LVC240A's 6.5ns propagation delay and low ground bounce further support reliable high-speed redriving without external amplification.

What is the difference between SN74LVC240A and SN74LVC244A?

The SN74LVC240A features two independent active-low output enables (1OE, 2OE) controlling separate 4-channel banks, whereas the SN74LVC244A uses a single OE pin for all eight channels. Both share identical electrical specs and pinout compatibility, but the SN74LVC240A enables finer-grained bus segmentation-e.g., holding memory address lines while releasing data lines during reset. The SN74LVC240A is preferred when bank-level isolation is required.

Does the SN74LVC240A include Schmitt-trigger inputs?

No-the SN74LVC240A uses standard CMOS inputs without hysteresis. Its inputs require fast transitions (<6 ns/V) and must be terminated to valid logic levels (VCC or GND) to avoid oscillation or excessive power draw. Unlike Schmitt-trigger variants, the SN74LVC240A does not provide noise immunity for slow-rising signals; external RC filtering or dedicated Schmitt buffers (e.g., SN74LVC14) are needed for noisy environments. This design choice prioritizes speed and low capacitance (Ci = 4pF) over noise rejection.