Texas Instruments SN74HCT240DWR

Overview

SN74HCT240DWR from Texas Instruments is an octal inverting buffer/line driver with 3-state outputs, designed for memory address and bus driving in 5V TTL-compatible systems. It operates from 4.5V to 5.5V, delivers ±6mA output drive per channel, exhibits 12ns typical propagation delay at 5V, and draws ≤80μA quiescent current - enabling high-density bus interfacing in industrial control backplanes.

For engineers reviewing the SN74HCT240DWR datasheet, SN74HCT240DWR pinout, SN74HCT240DWR application, or SN74HCT240DWR equivalent, this page provides verified functional modes, SOIC-20 package dimensions, 3-state timing parameters (tpd, ten, tdis), input voltage compatibility (VIH = 2V, VIL = 0.8V), and validated alternatives for bus buffering upgrades.

Technical Context

The SN74HCT240DWR implements two independent 4-bit inverting buffers, each with dedicated output-enable (OE) control. Its logic function is strictly inverting: when OE is low, Y = NOT(A); when OE is high, all Y outputs enter high-impedance state. This architecture enables bidirectional bus control without external inversion logic.

All inputs are TTL-voltage compatible (VIH ≥ 2V, VIL ≤ 0.8V at VCC = 4.5–5.5V), and outputs drive up to 15 LSTTL loads while maintaining VOH ≥ 3.7V and VOL ≤ 0.33V under 6mA load. The device supports CL = 50pF and CL = 150pF switching conditions with fully characterized tpd, ten, and tdis across temperature.

Key Specifications

Pinout & Package

SN74HCT240DWR is housed in a 20-pin SOIC (DW) package measuring 12.80mm × 10.3mm (body: 12.80mm × 7.50mm), RoHS-compliant with NiPdAu lead finish and MSL Level-1 rating.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HCT240NSR and SN74ACT240DWR, the SN74HCT240DWR offers optimal balance of industrial-grade thermal performance (RθJA = 109.1°C/W), proven SOIC manufacturability, and ultra-low standby power - making it preferred for cost-sensitive, thermally constrained, or legacy-replacement applications.

Availability

SN74HCT240DWR is available at Aetrix Electronics and suitable for industrial backplane interfaces, microcontroller bus expansion, and legacy system upgrades requiring stable component supply and long-term obsolescence management.

Supply support for SN74HCT240DWR 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 SN74HCT240DWR belongs to TI's 74HCT logic family, engineered for TTL-compatible 5V systems requiring low power, high noise immunity, and robust 3-state bus driving capability in industrial control and instrumentation.

FAQ

What is the logic function of SN74HCT240DWR?

The SN74HCT240DWR implements two independent 4-bit inverting buffers with 3-state outputs. When its output-enable inputs (1OE or 2OE) are low, it passes inverted data from A inputs to Y outputs (Y = NOT(A)). When OE is high, the corresponding Y outputs enter high-impedance state. This behavior is confirmed in the Function Table (Table 6-1) and applies identically to both buffer groups within SN74HCT240DWR.

Does SN74HCT240DWR support 3.3V logic inputs?

No, SN74HCT240DWR does not reliably accept 3.3V logic inputs. Its input thresholds are TTL-compatible: VIH = 2.0V minimum and VIL = 0.8V maximum at VCC = 4.5–5.5V. While a 3.3V high signal may exceed VIH, it falls outside the guaranteed operating range and risks marginal switching or increased susceptibility to noise. For mixed-voltage systems, use a dedicated level shifter or 3.3V-compatible logic family instead of relying on SN74HCT240DWR.

What is the maximum capacitive load SN74HCT240DWR can drive?

SN74HCT240DWR is characterized for CL = 50pF and CL = 150pF in its switching specifications. At CL = 150pF, typical propagation delay increases to 19ns (5.5V) and enable/disable times extend to 40–48ns. Driving loads beyond 150pF will further degrade timing margins and may cause signal integrity issues. For heavier loads, add series termination or reduce trace length - the SN74HCT240DWR itself is not rated for >150pF operation.

Can unused inputs on SN74HCT240DWR be left floating?

No, unused inputs on SN74HCT240DWR must never be left floating. As stated in Section 4.2 and Layout Guidelines (Section 7.2.1), all unused inputs must be tied to VCC or GND to prevent undefined operational states, increased ICC, and potential oscillation. Floating inputs cause unpredictable current draw and noise coupling - TI explicitly mandates termination to defined logic levels for reliable SN74HCT240DWR operation.

Is SN74HCT240DWR pin-compatible with SN74LS240?

Yes, SN74HCT240DWR is pin-compatible and functionally equivalent to SN74LS240 in SOIC-20 (DW) packaging, sharing identical pin configuration, logic function, and 3-state behavior. However, SN74HCT240DWR uses CMOS technology - delivering lower ICC (80μA vs. 25mA), higher noise immunity, and improved output drive (±6mA vs. ±8mA) while maintaining TTL input compatibility. This makes SN74HCT240DWR a direct, drop-in upgrade for SN74LS240 in existing designs.