Texas Instruments SN74HCT240DGSR

Overview

SN74HCT240DGSR from Texas Instruments is an octal inverting buffer/line driver with 3-state outputs, designed for memory address and bus driving in industrial and embedded systems. It operates at 4.5–5.5 V, delivers ±6 mA output drive per channel, exhibits 12 ns typical propagation delay at 5.5 V, and draws ≤80 μA quiescent current. Its dual 4-bit architecture with independent OE controls enables selective bus isolation in high-density PCB layouts.

For engineers reviewing the SN74HCT240DGSR datasheet, SN74HCT240DGSR pinout, SN74HCT240DGSR application, or SN74HCT240DGSR equivalent, key selection criteria include TTL-compatible input thresholds, 3-state output timing (ten/tdis ≤40 ns), thermal performance in VSSOP (RθJA = 130.6°C/W), and compatibility with 50 pF–150 pF bus loads in memory and clock distribution networks.

Technical Context

The SN74HCT240DGSR implements two independent 4-bit inverting buffers, each with dedicated output-enable (OE) inputs controlling high-impedance state entry/exit. Its logic function follows a strict inversion: when OE is low, Y = NOT(A); when OE is high, all Y outputs enter high-Z. This architecture supports bidirectional bus control without external logic.

Designed for 5-V TTL-level systems, it features input thresholds aligned to standard TTL (VIH = 2.0 V min, VIL = 0.8 V max), rail-to-rail output swing (VOH ≥ 3.7 V at 6 mA, VOL ≤ 0.33 V), and robust noise immunity (input hysteresis not specified, but VIH/VIL margins ensure reliable switching under noisy conditions).

Key Specifications

Pinout & Package

VSSOP-20 (DGS) package: 5.1 mm × 4.9 mm footprint, 1.1 mm max height, exposed thermal pad, 0.5 mm pitch, RoHS-compliant NiPdAu lead finish, MSL Level-1.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HCT240DWR and SN74LV240APWR, the SN74HCT240DGSR offers the smallest PCB footprint and highest thermal resistance, making it optimal for space-constrained industrial modules where 5-V operation and fast enable timing are critical - but requires careful thermal management above 70°C ambient.

Availability

SN74HCT240DGSR is available at Aetrix Electronics and suitable for industrial control systems, programmable logic controllers, and embedded memory subsystems requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for SN74HCT240DGSR 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 experience in industrial-grade interface and buffering ICs.

The SN74HCT240DGSR belongs to TI's HCT logic family, engineered for seamless 5-V TTL interoperability and high-noise-immunity bus interfacing in mission-critical industrial and automotive applications.

FAQ

What is the maximum operating temperature for SN74HCT240DGSR?

The SN74HCT240DGSR is rated for operation from –40°C to +125°C. This extended industrial temperature range allows deployment in harsh environments such as motor drives, factory automation controllers, and outdoor communication equipment where ambient temperatures exceed standard commercial limits. The VSSOP package's thermal characteristics (RθJA = 130.6°C/W) require appropriate PCB copper area and thermal vias to maintain junction temperature below 150°C at full load.

Does SN74HCT240DGSR support non-inverting operation?

No, the SN74HCT240DGSR is strictly an inverting octal buffer: each Y output equals the logical inverse of its corresponding A input when enabled. There is no internal configuration or external pin to disable inversion. For non-inverting functionality, TI recommends the companion part SN74HCT244DGSR, which provides identical packaging, timing, and drive strength but with true (non-inverting) buffer logic.

Can SN74HCT240DGSR drive a 150-pF capacitive load reliably?

Yes, the SN74HCT240DGSR is characterized for CL = 150 pF, with tpd ≤56 ns and ten/tdis ≤71 ns at 5.5 V. Its ±6 mA output drive ensures adequate slew rate to charge/discharge this load within timing budgets for 10–15 MHz bus applications. Layout best practices-short traces, ground plane proximity, and proper termination-remain essential to avoid ringing or overshoot.

Is SN74HCT240DGSR pin-compatible with SN74HCT240DWR?

Yes, SN74HCT240DGSR and SN74HCT240DWR share identical pin functions and numbering (20-pin VSSOP vs SOIC), enabling direct PCB footprint substitution. However, the VSSOP package has a smaller body (5.1 mm × 4.9 mm vs 12.8 mm × 10.3 mm) and requires adjusted stencil aperture design and reflow profile due to finer pitch (0.5 mm vs 1.27 mm) and exposed thermal pad.

What is the purpose of the exposed thermal pad on SN74HCT240DGSR?

The exposed thermal pad on SN74HCT240DGSR serves as the primary thermal conduction path from the die to the PCB. It must be soldered to a solid copper pour connected to internal ground planes via ≥4 thermal vias (0.3 mm diameter, spaced ≤1 mm apart). Proper implementation reduces junction-to-board thermal resistance (RθJB) to 85.4°C/W, preventing thermal shutdown during sustained 6-mA output loading at elevated ambient temperatures.