Texas Instruments SN74HC240DWR

Overview

SN74HC240DWR from Texas Instruments is an octal inverting buffer/line driver with 3-state outputs, designed for memory address and bus driving applications. It operates from 2V to 6V, delivers ±6mA output drive at 5V, exhibits typical propagation delay of 9ns, and consumes ≤80µA ICC - enabling high-density, low-power bus interfacing in industrial control and embedded systems.

For engineers reviewing the SN74HC240DWR datasheet, SN74HC240DWR pinout, SN74HC240DWR application, or SN74HC240DWR equivalent, this page provides verified functional modes, SOIC-20 package details, 3-state timing parameters (tpd, ten, tdis), and validated alternative options for bus buffering and address driver replacement.

Technical Context

The SN74HC240DWR implements two independent 4-bit inverting buffers, each controlled by a dedicated output-enable (OE) input. When OE is low, inverted data passes from A inputs to Y outputs; when OE is high, all eight outputs enter high-impedance state - enabling bidirectional bus sharing without external logic.

Its CMOS HCMOS architecture ensures rail-to-rail output swing, low input current (≤1µA), and compatibility with LSTTL loads (up to 15). The device supports wide VCC range (2–6V), making it suitable for mixed-voltage system interfacing between 3.3V and 5V domains.

Key Specifications

Pinout & Package

SN74HC240DWR 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 SN74HC240DWR, SN74HCT240DWR trades lower power for improved TTL input compatibility, while 74LVC240APW offers superior speed and drive at the cost of narrower voltage range and non-SOIC packaging - guiding selection based on voltage domain, noise environment, and layout constraints.

Availability

SN74HC240DWR is available at Aetrix Electronics and suitable for industrial control systems, embedded memory interfaces, and legacy peripheral adapters requiring stable component supply and long-term manufacturability.

Supply support for SN74HC240DWR 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, automotive, and communications markets.

The SN74HC240 series belongs to TI's industry-standard 74HC logic family, engineered for high-density, low-power bus interfacing in memory subsystems, clock distribution networks, and programmable logic support circuits.

FAQ

What is the function of the OE pins on SN74HC240DWR?

The SN74HC240DWR features two active-low output-enable pins (1OE on Pin 1 and 2OE on Pin 19) that independently control the 3-state output behavior of each 4-bit buffer section. When OE is low, the corresponding Y outputs invert and pass A-input data; when high, those outputs enter high-impedance state - enabling precise bus arbitration and multi-driver sharing without contention. This dual-OE architecture is integral to the SN74HC240DWR's role in memory-mapped I/O systems.

Can SN74HC240DWR operate at 3.3V supply voltage?

Yes, SN74HC240DWR is fully specified for operation from 2V to 6V, including 3.3V nominal supply. At VCC = 3.3V, it maintains guaranteed VOH ≥ 3.15V (VIH min) and VOL ≤ 0.33V (IOL = 6mA), ensuring reliable interfacing with 3.3V microcontrollers and FPGAs. Its HCMOS design guarantees rail-compatible logic thresholds across the full voltage range, making SN74HC240DWR suitable for mixed-voltage board designs without level translation.

What is the maximum capacitive load SN74HC240DWR can drive reliably?

SN74HC240DWR is characterized for CL = 50pF and CL = 150pF in its switching specifications. At VCC = 4.5V, tpd remains ≤38ns even at 150pF, confirming stable operation into moderate PCB trace and IC input capacitance. While not rated for transmission-line driving, SN74HC240DWR reliably drives up to 15 LSTTL loads (≈450pF total) per output, provided layout follows best practices: short traces, ground plane, and local 0.1µF bypassing - all validated in SN74HC240DWR application testing.

Is SN74HC240DWR pin-compatible with other 74HC240 variants?

Yes, SN74HC240DWR shares identical pinout, logic function, and electrical specifications with all standard 74HC240 variants in SOIC-20 (DW) packaging, including SN74HC240N (PDIP) and SN74HC240PW (TSSOP), per TI's SCLS128H datasheet. The SN74HC240DWR pin configuration matches the functional block diagram and Table 3-1 exactly - confirming direct PCB substitution within the same package family. However, cross-package replacements require footprint adaptation.

Does SN74HC240DWR require external pull-up resistors on OE inputs?

No, SN74HC240DWR OE inputs are CMOS-compatible and do not require external pull-ups when driven actively by microcontroller GPIO or logic gates. However, if left unconnected, OE floats near VCC/2 and may cause partial turn-on and excessive ICC - so TI mandates tying unused OE pins to GND (to enable) or VCC (to disable). For robust industrial designs, SN74HC240DWR OE lines should be actively driven or pulled to defined logic states using ≤10kΩ resistors, per Section 4.2 of the datasheet.