Texas Instruments CD74HCT240PWT

Overview

CD74HCT240PWT from Texas Instruments is an inverting octal buffer/line driver with dual active-low three-state output enables, designed for bidirectional bus interfacing in 5-V TTL-compatible digital systems. It delivers 8ns typical propagation delay at V_CC = 5 V, CL = 15 pF, supports ±25 mA output drive per channel, operates across –55°C to +125°C, and features high-current bus driver outputs for robust signal integrity in industrial control backplanes.

For engineers reviewing the CD74HCT240PWT datasheet, CD74HCT240PWT pinout, CD74HCT240PWT application, or CD74HCT240PWT equivalent, key selection criteria include its inverting logic function, dual active-low OE control, LSTTL input compatibility (V_IL ≤ 0.8 V, V_IH ≥ 2.0 V), 4.5–5.5 V supply range, and TSSOP-20 package thermal performance (R_θJA = 131.8°C/W).

Technical Context

The CD74HCT240PWT implements eight independent inverting buffer channels, each with separate enable control via two shared active-low output enable inputs (1OE and 2OE). Its HCT logic family ensures direct compatibility with standard LSTTL outputs while maintaining CMOS power efficiency and noise immunity.

Each channel provides three-state output capability with controlled transition times (12–18 ns typical), low output leakage (<±5 μA), and balanced t_PLH/t_PHL propagation characteristics-critical for synchronous bus arbitration and glitch-free data latching in high-density PCB layouts.

Key Specifications

Pinout & Package

Packaged in a 20-pin TSSOP (PW) with 0.65 mm pitch, body size 6.50 mm × 4.40 mm, and exposed pad not present - optimized for automated SMT assembly and space-constrained industrial controllers.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HCT240PW and 74HCT240D,653, the CD74HCT240PWT offers identical functionality in a smaller TSSOP footprint with superior board-area efficiency, though at a modest thermal penalty - making it optimal for space-constrained industrial controllers where layout density outweighs peak power dissipation concerns.

Availability

CD74HCT240PWT is available at Aetrix Electronics and suitable for industrial backplane interfaces, automotive ECU data buses, and avionics data acquisition systems requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for CD74HCT240PWT 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 delivering analog and embedded processing solutions for industrial, automotive, and communications markets.

The CD74HCT240PWT belongs to TI's legacy high-speed CMOS logic portfolio, engineered specifically for robust 5-V bus interfacing in harsh-environment applications demanding wide temperature operation and LSTTL compatibility.

FAQ

What logic function does the CD74HCT240PWT implement?

The CD74HCT240PWT implements eight independent inverting buffer channels grouped into two banks of four, each controlled by an active-low output enable (1OE and 2OE). It performs true logical inversion (Y = NOT A) on all inputs and enters high-impedance state when either OE is high - enabling bidirectional bus control in systems like industrial PLC backplanes and test equipment.

Can the CD74HCT240PWT operate outside the 4.5–5.5 V supply range?

No. The CD74HCT240PWT is specified only for 4.5 V to 5.5 V operation per its HCT family design. Operation below 4.5 V risks unreliable LSTTL input recognition (V_IL/V_IH thresholds shift), while exceeding 5.5 V violates absolute maximum ratings and may cause permanent damage. For wider supply ranges, consider HC-family variants like CD74HC240PWT (2–6 V), but note their lack of native LSTTL compatibility.

How does the CD74HCT240PWT handle unused inputs?

All unused inputs on the CD74HCT240PWT must be tied to a valid logic level - either V_CC or GND - to prevent floating nodes that induce excessive supply current, noise coupling, or undefined output states. Leaving inputs unconnected violates TI's layout guidelines and may cause erratic behavior, especially under temperature extremes or EMI exposure. Unused OEs should be held low to avoid unintended three-state activation.

What is the maximum capacitive load the CD74HCT240PWT can drive reliably?

The CD74HCT240PWT is characterized up to 50 pF load capacitance in its switching specifications (t_PLH, t_PHL, t_THL). While it can physically drive heavier loads, propagation delay increases linearly with C_L, and output transition times degrade - potentially violating setup/hold timing in synchronous systems. For >50 pF loads, verify timing margins using the device's C_PD = 40 pF and measured t_PLH/t_PHL vs. C_L curves from the datasheet.

Is the CD74HCT240PWT RoHS compliant?

Yes. The CD74HCT240PWT carries "Yes" in the RoHS column of TI's official packaging addendum, confirming compliance with EU Directive 2011/65/EU. Its lead finish is NiPdAu (NIPDAU), and it meets JEDEC J-STD-020 moisture sensitivity level requirements - critical for reflow soldering in modern electronics manufacturing.