Texas Instruments SN74HC240PWT

Overview

SN74HC240PWT 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, features typical propagation delay of 9ns (VCC = 4.5V, CL = 50pF), and consumes ≤80µA ICC. Its dual 4-bit architecture with independent OE controls enables selective bus isolation in high-density digital systems.

For engineers reviewing the SN74HC240PWT datasheet, SN74HC240PWT pinout, SN74HC240PWT application, or SN74HC240PWT equivalent, key selection criteria include its 3-state output behavior, inverted logic function per channel, TSSOP-20 package footprint, wide supply voltage range, and compatibility with LSTTL load driving requirements in memory and clock distribution circuits.

Technical Context

The SN74HC240PWT implements two independent 4-bit inverting buffer sections, each with dedicated output-enable (OE) inputs. When OE is low, data passes from A inputs to Y outputs with inversion; when OE is high, all eight outputs enter high-impedance state-enabling bidirectional bus control without external direction logic.

Its CMOS HCMOS process ensures rail-to-rail input thresholds, low static current (≤1µA max input leakage), and robust noise immunity. The device supports mixed-voltage interfacing across 2V–6V operation and meets JEDEC JESD78 Class II latch-up immunity standards.

Key Specifications

Pinout & Package

TSSOP-20 package (PW), 6.50mm × 6.4mm body size, 0.65mm lead pitch, 2mm max height - optimized for compact PCB layouts and automated assembly.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HC240PWT, SN74HCT240PWR offers TTL-input compatibility at the cost of higher static current, while 74LVC240APW,118 delivers faster switching and lower voltage operation but lacks 5V tolerance - making SN74HC240PWT the optimal choice for mixed 3.3V/5V industrial bus buffering.

Availability

SN74HC240PWT is available at Aetrix Electronics and suitable for industrial control systems, memory subsystems, and legacy bus interface designs requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for SN74HC240PWT 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 SN74HC240PWT belongs to TI's 74HC logic family, engineered for high-speed, low-power, pin-compatible replacements of legacy TTL devices in memory addressing, clock distribution, and bus interface applications.

FAQ

What is the logic function of SN74HC240PWT?

The SN74HC240PWT provides eight inverting buffer/driver channels organized as two independent 4-bit groups. Each group has its own active-low output-enable (OE) input. When OE is low, the device passes inverted data from A inputs to Y outputs; when OE is high, all Y outputs enter high-impedance state. This behavior is confirmed in the Function Table (Table 6-1) and Pin Functions table of the official datasheet.

Does SN74HC240PWT support 3.3V operation?

Yes, SN74HC240PWT fully supports 3.3V operation within its specified 2V–6V supply range. At VCC = 3.3V, it delivers ≥±4mA output drive, maintains VIH/VIL thresholds compatible with 3.3V CMOS logic, and achieves typical tpd of ~12ns (CL = 50pF). These values are verified in Sections 4.2 and 4.5 of the SCLS128H datasheet.

What is the thermal resistance (RθJA) for SN74HC240PWT in TSSOP-20 package?

The SN74HC240PWT in PW (TSSOP-20) package has a junction-to-ambient thermal resistance (RθJA) of 131.8°C/W, as specified in Section 4.3 of the datasheet. This value assumes standard JEDEC 2-layer board conditions and informs thermal design for continuous operation up to +85°C ambient temperature.

Can unused inputs on SN74HC240PWT be left floating?

No - all unused inputs on SN74HC240PWT must be tied to VCC or GND to prevent undefined logic states and excessive current draw. Section 4.2 of the datasheet explicitly states: "All unused inputs of the device must be held at VCC or GND to ensure proper device operation." Floating inputs may cause oscillation, increased ICC, or latch-up in CMOS logic.

Is SN74HC240PWT RoHS compliant and lead-free?

Yes, SN74HC240PWT is RoHS compliant and uses NiPdAu (NIPDAU) lead finish, as documented in the PACKAGE OPTION ADDENDUM (page Addendum-Page 1). It carries MSL Level-1 rating with unlimited floor life and peak reflow temperature of 260°C, meeting IPC/JEDEC J-STD-020 requirements for lead-free assembly.