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Home > Products > Integrated Circuits (ICs) > Logic > Buffers, Drivers, Receivers, Transceivers

Texas Instruments CD74HCT240EG4

Name: CD74HCT240EG4
Brand: Texas Instruments
SKU: CD74HCT240EG4
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: CD74HCT240EG4

Manufacturer:: Texas Instruments

Category:: Buffers, Drivers, Receivers, Transceivers

Package:: 20-DIP (0.300", 7.62mm)

Datasheet:: CD74HCT240EG4.pdf

Description:: IC BUFFER INVERT 5.5V 20DIP

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Product details

Overview

CD74HCT240EG4 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 pin, operates across –55°C to +125°C, and features buffered inputs and high-current bus-driver outputs.

For engineers reviewing the CD74HCT240EG4 datasheet, CD74HCT240EG4 pinout, CD74HCT240EG4 application, or CD74HCT240EG4 equivalent, this device is selected for robust 5-V logic-level translation, high-fanout bus buffering, and noise-immune signal isolation in industrial control backplanes and legacy microprocessor data buses.

Technical Context

The CD74HCT240EG4 implements two independent 4-bit inverting buffers, each controlled by its own active-low output enable (1OE, 2OE). Its HCT logic family ensures direct LSTTL input compatibility (V_IL ≤ 0.8 V, V_IH ≥ 2.0 V) while maintaining CMOS power efficiency and input leakage ≤1 μA at V_CC = 5.5 V.

All eight outputs enter high-impedance state when either enable is asserted low; both enables must be high for functional output. Propagation delays are balanced (t_PLH ≈ t_PHL), and transition times are tightly controlled (12–18 ns typical), enabling clean edge integrity in synchronous bus environments.

Key Specifications

Parameter	Value and Actual Design Meaning
Logic Family	HCT - TTL-compatible input thresholds, 4.5–5.5 V operation, enables direct replacement of 74LS240 without level-shifting.
Propagation Delay	9 ns typical (V_CC = 4.5 V, C_L = 50 pF) - ensures sub-10 ns timing margin for 50-MHz bus cycles.
Output Drive	±25 mA per output - drives 15 LSTTL loads, sufficient for terminated parallel buses and multi-drop control lines.
Operating Temperature	–55°C to +125°C - qualified for extended industrial, aerospace, and under-hood automotive subsystems.
Three-State Enable	Dual active-low OE pins (1OE, 2OE) - allows independent gating of two 4-bit channels for dynamic bus arbitration.
Input Leakage	≤1 μA at V_CC = 5.5 V - minimizes static current draw in battery-backed or low-power standby modes.
Power Dissipation Cap.	40 pF - used to calculate dynamic power: P_D = V_CC² × f_i × (C_PD + C_L), critical for thermal budgeting in dense PCB layouts.

Pinout & Package

Packaged in 20-pin PDIP (plastic dual in-line package) with 0.300-inch body width and through-hole mounting. Pin pitch is 0.100 inch; leads are tin-lead (NIPDAU) finish, RoHS-compliant.

Pin/Terminal	Circuit Role	Design Meaning
1, 2, 3, 4, 5, 6, 7, 8	Inputs (1A1–1A4, 2A1–2A4)	Inverting data inputs for two independent 4-bit channels; buffered to reduce capacitive loading on upstream drivers.
9, 10, 11, 12, 13, 14, 15, 16	Outputs (1Y1–1Y4, 2Y1–2Y4)	Inverting buffered outputs; each sinks or sources up to ±25 mA in active state, high-Z when corresponding OE is low.
17, 18	Output Enables (1OE, 2OE)	Active-low controls: pulling either pin low disables its associated 4-bit output group; both must be high for output functionality.
19	GND	Ground reference for all logic and I/O; must be low-impedance connection to minimize ground bounce in high-speed switching.
20	V_CC	+5 V supply (4.5–5.5 V); requires local 0.1-μF ceramic bypass capacitor placed adjacent to pin for stable switching performance.

Key Features

Feature	Design Value
Inverting three-state logic	Enables bidirectional bus control with polarity inversion built-in - eliminates need for external inverters in address/data complement paths.
Two independent OE controls	Allows selective disabling of upper/lower nibbles for partial bus isolation - essential for memory-mapped I/O and peripheral multiplexing.
TTL-compatible input thresholds	V_IL ≤ 0.8 V / V_IH ≥ 2.0 V ensures reliable interfacing with legacy 74LS and 74F families without pull-up resistors or level shifters.
High-noise immunity design	CMOS input structure with II ≤ 1 μA reduces susceptibility to crosstalk and EMI in noisy industrial enclosures.
Wide temperature range support	–55°C to +125°C operation validated per MIL-PRF-38535 - suitable for avionics, downhole tools, and engine-control modules.

Applications

Industrial PLC Backplane Interface	Legacy Microprocessor Data Bus Driver
Use Scenario: Isolating and driving 8-bit data lines between CPU and modular I/O cards in programmable logic controllers. IC Role / Device Role / Timing Role: Inverting three-state buffer providing direction-controlled data path isolation and fanout expansion. Use Value: Dual OE pins allow real-time channel gating during bus arbitration; ±25 mA drive sustains signal integrity over 15-cm backplane traces.	Use Scenario: Interfacing Z80 or 8085 microprocessors with peripheral chips requiring inverted data strobes and bus contention management. IC Role / Device Role / Timing Role: Octal inverting buffer with precise 9 ns propagation delay ensuring setup/hold compliance in 4–6 MHz CPU buses. Use Value: TTL-compatible inputs eliminate external level-shifting; wide temperature range supports uncooled rack-mounted designs.
Automotive Engine Control Module (ECM)	Test Equipment Signal Conditioning
Use Scenario: Buffering sensor calibration signals and actuator command lines within engine control units exposed to under-hood thermal cycling. IC Role / Device Role / Timing Role: High-reliability inverting line driver operating across –40°C to +125°C ambient, supporting diagnostic mode sequencing. Use Value: Validated –55°C to +125°C operation exceeds AEC-Q100 Grade 1 requirements; low ICC (≤160 μA) reduces idle power in sleep modes.	Use Scenario: Conditioning digital stimulus signals in automated test equipment where signal inversion and bus isolation are required between DUT and controller. IC Role / Device Role / Timing Role: Precision inverting buffer with matched t_PLH/t_PHL enabling deterministic edge alignment in pattern generators. Use Value: 12–18 ns transition time control minimizes jitter; three-state capability supports multi-DUT parallel testing architectures.

Industrial PLC Backplane Interface

Legacy Microprocessor Data Bus Driver

Use Scenario: Isolating and driving 8-bit data lines between CPU and modular I/O cards in programmable logic controllers.

IC Role / Device Role / Timing Role: Inverting three-state buffer providing direction-controlled data path isolation and fanout expansion.

Use Value: Dual OE pins allow real-time channel gating during bus arbitration; ±25 mA drive sustains signal integrity over 15-cm backplane traces.

Use Scenario: Interfacing Z80 or 8085 microprocessors with peripheral chips requiring inverted data strobes and bus contention management.

IC Role / Device Role / Timing Role: Octal inverting buffer with precise 9 ns propagation delay ensuring setup/hold compliance in 4–6 MHz CPU buses.

Use Value: TTL-compatible inputs eliminate external level-shifting; wide temperature range supports uncooled rack-mounted designs.

Automotive Engine Control Module (ECM)

Test Equipment Signal Conditioning

Use Scenario: Buffering sensor calibration signals and actuator command lines within engine control units exposed to under-hood thermal cycling.

IC Role / Device Role / Timing Role: High-reliability inverting line driver operating across –40°C to +125°C ambient, supporting diagnostic mode sequencing.

Use Value: Validated –55°C to +125°C operation exceeds AEC-Q100 Grade 1 requirements; low ICC (≤160 μA) reduces idle power in sleep modes.

Use Scenario: Conditioning digital stimulus signals in automated test equipment where signal inversion and bus isolation are required between DUT and controller.

IC Role / Device Role / Timing Role: Precision inverting buffer with matched t_PLH/t_PHL enabling deterministic edge alignment in pattern generators.

Use Value: 12–18 ns transition time control minimizes jitter; three-state capability supports multi-DUT parallel testing architectures.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
SN74HCT240N	Same logic function, pinout, and electrical specs; identical HCT family, but manufactured by TI with different orderable suffix and packaging (N = PDIP).	No functional difference; SN74HCT240N is a direct second-source variant with identical qualification and traceability.	Select SN74HCT240N if standard TI part numbering is required for BOM consistency or legacy procurement workflows.
74HCT240D	SOIC-20 package (3.9 mm width), not PDIP; same electrical behavior but smaller footprint and surface-mount assembly.	Requires PCB redesign for SMT placement; unsuitable for through-hole prototyping or repair scenarios where CD74HCT240EG4's PDIP is mandated.	Choose 74HCT240D only when board space constraints necessitate SOIC packaging and reflow soldering is available.

Compared with CD74HCT240EG4, SN74HCT240N offers identical performance in the same PDIP package for seamless substitution, while 74HCT240D trades through-hole compatibility for compactness-making the former ideal for drop-in replacement and the latter for space-constrained production designs.

Availability

CD74HCT240EG4 is available at Aetrix Electronics and suitable for industrial PLC backplanes, legacy microprocessor data buses, and automotive engine control modules requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for CD74HCT240EG4 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, embedded processing, and logic solutions for industrial, automotive, and communications markets.

The CD74HCT240EG4 belongs to TI's legacy high-speed CMOS logic portfolio, engineered specifically for robust 5-V TTL-compatible interfacing in mission-critical systems where reliability, wide temperature operation, and bus-driving capability are mandatory.

FAQ

What is the maximum output current per pin for CD74HCT240EG4?

The CD74HCT240EG4 supports ±25 mA output source/sink current per pin under recommended operating conditions (V_CC = 4.5–5.5 V, T_A = –55°C to +125°C). This rating enables direct driving of 15 LSTTL loads and ensures signal integrity on moderately loaded PCB traces without external amplification. Exceeding ±25 mA risks parametric shift or latch-up.

Does CD74HCT240EG4 require external pull-up resistors on its inputs?

No, CD74HCT240EG4 does not require external pull-up resistors on its inputs. Its HCT family inputs meet LSTTL voltage thresholds (V_IL ≤ 0.8 V, V_IH ≥ 2.0 V) and exhibit low input leakage (≤1 μA), allowing direct connection to open-collector or tri-stated sources without biasing. Unused inputs should be tied to V_CC or GND to prevent floating states.

Can CD74HCT240EG4 operate at 3.3 V supply voltage?

No, CD74HCT240EG4 is not specified for 3.3 V operation. Its HCT family requires V_CC = 4.5–5.5 V to guarantee TTL-compatible input thresholds and full output drive capability. For 3.3 V systems, consider the CD74HC240E (HC family, 2–6 V) or SN74LVC240A (LVC family, 1.65–3.6 V) instead.

What is the propagation delay variation between CD74HCT240EG4 and CD74HC240E?

At V_CC = 5 V and C_L = 50 pF, CD74HCT240EG4 exhibits 9 ns typical propagation delay, while CD74HC240E shows 8 ns typical under identical conditions. The HCT version prioritizes input compatibility over speed; both meet sub-25 ns max delay across temperature, but HCT's tighter VIH/VIL specs ensure interoperability with older TTL families.

How are the two output enable pins (1OE and 2OE) used in system design?

In CD74HCT240EG4, 1OE controls outputs Y1–Y4 and 2OE controls Y5–Y8. Asserting either low disables its respective 4-bit group into high-impedance state, enabling independent bus segment control. This allows dynamic partitioning of an 8-bit bus-for example, isolating upper/nibbles during DMA transfers or peripheral configuration sequences without software overhead.

CD74HCT240EG4 Specifications

Product attributes: Attribute value

Manufacturer:: Texas Instruments

Series:: 74HCT

Package/Case:: 20-DIP (0.300", 7.62mm)

Packaging:: Tube

Product Status:: Discontinued at Digi-Key

Logic Type:: Buffer, Inverting

Number of Elements:: 2

Number of Bits per Element:: 4

Input Type:: -

Output Type:: 3-State

Current - Output High, Low:: 6mA, 6mA

Voltage - Supply:: 4.5V ~ 5.5V

Operating Temperature:: -55°C ~ 125°C (TA)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: 20-PDIP

CD74HCT240EG4 FAQ

1.How can I place an order for CD74HCT240EG4 through Aetrix?

Please submit a Request for Quotation (RFQ) for CD74HCT240EG4 on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for CD74HCT240EG4 reliable?

The price and inventory of CD74HCT240EG4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for CD74HCT240EG4 is usually 5 days.

3.What payment methods are accepted for CD74HCT240EG4?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for CD74HCT240EG4 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for CD74HCT240EG4?

CD74HCT240EG4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your CD74HCT240EG4 order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for CD74HCT240EG4?

For technical support, including CD74HCT240EG4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your CD74HCT240EG4 requirements.

6.How does Aetrix verify that CD74HCT240EG4 is sourced from the original manufacturer or authorized distributors?

All CD74HCT240EG4 products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that CD74HCT240EG4 meets industry standards.

7.What is the process for return or replacement of CD74HCT240EG4?

All CD74HCT240EG4 units undergo pre-shipment inspection (PSI). If there is an issue with CD74HCT240EG4, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The CD74HCT240EG4 part is unused and in its original packaging.

Return procedure for CD74HCT240EG4:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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