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

onsemi MC74AC240MELG

Name: MC74AC240MELG
Brand: onsemi
SKU: MC74AC240MELG
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: MC74AC240MELG

Manufacturer:: onsemi

Category:: Buffers, Drivers, Receivers, Transceivers

Package:: 20-SOIC (0.209", 5.30mm Width)

Datasheet:: MC74AC240MELG.pdf

Description:: IC BUFF INVERT 6V SOEIAJ-20

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Product details

Overview

MC74AC240MELG from onsemi is an octal 3-state buffer/line driver designed for memory address driving, clock distribution, and bidirectional bus interfacing in high-density PCB layouts. It operates from 2.0 V to 6.0 V, delivers ±24 mA output drive, supports −40°C to +85°C ambient operation, and features TTL-compatible inputs only in the ACT variant - not applicable to MC74AC240MELG.

For engineers reviewing the MC74AC240MELG datasheet, pinout, applications, or equivalent options, key selection criteria include its 20-pin SOIC-W package, dual independent 3-state enable control (OE1/OE2), AC-family input thresholds, and bus-hold–free CMOS logic compatibility in industrial memory and timing subsystems.

Technical Context

The MC74AC240MELG implements eight non-inverting buffers with two separate 3-state enable inputs (OE1 on pins 12/14/16/18; OE2 on pins 3/5/7/9), allowing independent control of two groups of four outputs. Its AC logic family uses CMOS technology with Schmitt-trigger–free inputs and rail-to-rail output swing.

It is rated for VCC = 2.0–6.0 V, guarantees tPLH/tPHL ≤ 7.0 ns at 5.0 V/50 pF, and maintains VOH ≥ 2.9 V (at VCC = 3.0 V, IOH = −24 mA) and VOL ≤ 0.44 V (at VCC = 5.5 V, IOL = 24 mA), enabling robust noise margin in mixed-voltage digital systems.

Key Specifications

Parameter	Value and Actual Design Meaning
VCC Range	2.0 V to 6.0 V - supports legacy 3.3 V and 5 V logic domains without level shifters
Output Drive	±24 mA - sufficient to drive 50-pF loads across 15 cm traces or 10 LVTTL inputs
Propagation Delay	≤ 7.0 ns @ 5.0 V/50 pF - enables reliable operation up to ~70 MHz bus toggle rates
3-State Enable Time	tPZH ≤ 8.0 ns @ 5.0 V - ensures fast bus arbitration and low glitch window during direction switching
Input Thresholds	VIH = 2.1 V min @ VCC = 3.0 V - compatible with 3.3 V CMOS and LVTTL logic families
Operating Temp	−40°C to +85°C - qualified for industrial temperature-grade embedded control and instrumentation
ESD Rating	>2000 V HBM - provides baseline handling robustness for assembly and field-replaceable modules

Pinout & Package

MC74AC240MELG is housed in a 20-lead SOIC-Wide (SOIC-20W) package per case 751D, with 1.27 mm pitch, 12.8 mm × 7.5 mm body, and Pb-free finish (G suffix).

Pin/Terminal	Circuit Role	Design Meaning
1, 2, 4, 6, 8, 10, 11, 13	Buffer Inputs (A1–A4, B1–B4)	Eight non-inverting data inputs grouped as two sets of four; no internal inversion or latching
12, 14, 16, 18	OE1 (Group A Output Enable)	Active-low enable controlling outputs Y1–Y4; tied together for synchronous group disable
3, 5, 7, 9	OE2 (Group B Output Enable)	Active-low enable controlling outputs Y5–Y8; independent of OE1 for split-bus control
15, 17, 19, 20, 1, 2, 4, 6, 8, 10	Outputs (Y1–Y8)	Eight 3-state CMOS outputs; high-impedance state entered when respective OE = HIGH
20	VCC	Positive supply pin - must be decoupled locally with 0.1 μF ceramic capacitor
10	GND	Ground reference - shared return for all inputs, outputs, and supply current paths

Key Features

Feature	Design Value
Dual independent 3-state enables	OE1 and OE2 allow concurrent control of two 4-bit bus segments - eliminates need for external gating logic
High-output drive (±24 mA)	Drives standard 50-pF loads at full speed without external buffers - reduces component count in address/data path
Wide VCC range (2.0–6.0 V)	Operates across 3.3 V and 5 V systems without redesign - simplifies migration from legacy 5 V designs
Pb-free SOIC-W package	RoHS-compliant 20-lead wide-body SOIC meets IPC/JEDEC standards for automated SMT assembly
Low quiescent ICC (≤ 80 µA)	Minimizes standby power in battery-backed or energy-sensitive applications such as portable test equipment

Applications

Memory Address Buffering	Microcontroller Bus Interface
Use Scenario: Driving 16-bit address lines from a microcontroller to multiple SRAM or Flash devices on a shared bus. IC Role / Device Role / Timing Role: Non-inverting octal buffer providing fanout and isolation between MCU address pins and memory device inputs. Use Value: Prevents capacitive loading-induced timing violations and ensures clean address transitions across 10+ cm PCB traces.	Use Scenario: Interfacing an 8-bit microcontroller's data bus to a peripheral requiring 3-state handshake control (e.g., LCD controller or ADC interface). IC Role / Device Role / Timing Role: Bidirectional bus driver enabling controlled data flow using OE1/OE2 for read/write direction management. Use Value: Eliminates need for discrete transceivers; enables precise timing alignment between MCU strobes and peripheral response windows.
Industrial Clock Distribution	Legacy System Signal Conditioning
Use Scenario: Distributing a system clock signal to multiple FPGA configuration ICs or CPLD JTAG chains. IC Role / Device Role / Timing Role: Low-skew, high-drive clock buffer with 3-state capability for dynamic clock gating during reconfiguration. Use Value: Maintains <7 ns propagation skew across all eight outputs, preserving setup/hold margins in multi-device clock trees.	Use Scenario: Level-shifting and buffering signals between 5 V legacy peripherals (e.g., ISA bus cards) and modern 3.3 V controllers. IC Role / Device Role / Timing Role: Voltage-tolerant CMOS buffer translating logic levels while preserving signal integrity and timing. Use Value: Operates reliably at VCC = 3.3 V with VIH = 2.1 V - accepts 3.3 V logic highs and drives 5 V-tolerant inputs without external resistors.

Memory Address Buffering

Microcontroller Bus Interface

Use Scenario: Driving 16-bit address lines from a microcontroller to multiple SRAM or Flash devices on a shared bus.

IC Role / Device Role / Timing Role: Non-inverting octal buffer providing fanout and isolation between MCU address pins and memory device inputs.

Use Value: Prevents capacitive loading-induced timing violations and ensures clean address transitions across 10+ cm PCB traces.

Use Scenario: Interfacing an 8-bit microcontroller's data bus to a peripheral requiring 3-state handshake control (e.g., LCD controller or ADC interface).

IC Role / Device Role / Timing Role: Bidirectional bus driver enabling controlled data flow using OE1/OE2 for read/write direction management.

Use Value: Eliminates need for discrete transceivers; enables precise timing alignment between MCU strobes and peripheral response windows.

Industrial Clock Distribution

Legacy System Signal Conditioning

Use Scenario: Distributing a system clock signal to multiple FPGA configuration ICs or CPLD JTAG chains.

IC Role / Device Role / Timing Role: Low-skew, high-drive clock buffer with 3-state capability for dynamic clock gating during reconfiguration.

Use Value: Maintains <7 ns propagation skew across all eight outputs, preserving setup/hold margins in multi-device clock trees.

Use Scenario: Level-shifting and buffering signals between 5 V legacy peripherals (e.g., ISA bus cards) and modern 3.3 V controllers.

IC Role / Device Role / Timing Role: Voltage-tolerant CMOS buffer translating logic levels while preserving signal integrity and timing.

Use Value: Operates reliably at VCC = 3.3 V with VIH = 2.1 V - accepts 3.3 V logic highs and drives 5 V-tolerant inputs without external resistors.

Equivalent & Alternatives

The following parts are listed as comparable options for similar octal 3-state buffer applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
SN74AC240N	Same AC logic family, identical pinout, but offered in PDIP-20 (not surface-mount); higher thermal resistance (JA = 110°C/W vs. 96°C/W)	Suitable for prototyping or through-hole legacy systems; not recommended for high-density SMT production	Select SN74AC240N only if DIP footprint and manual assembly are required.
MC74AC244MELG	Octal non-inverting buffer with single 3-state enable (OE) instead of dual OE1/OE2; otherwise identical AC specs and SOIC-20W packaging	Used where unified bus enable suffices; lacks independent group control needed for split-bus architectures	Choose MC74AC244MELG when simplified enable logic reduces firmware complexity or PCB routing overhead.

Compared with SN74AC240N and MC74AC244MELG, the MC74AC240MELG uniquely supports independent 3-state control of two 4-bit output groups - critical for segmented bus arbitration, memory banking, or dual-peripheral interfacing without added logic gates.

Availability

MC74AC240MELG is available at Aetrix Electronics and suitable for industrial control systems, memory expansion modules, and embedded instrumentation requiring stable component supply and long-term manufacturability.

Supply support for MC74AC240MELG 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

onsemi is a global semiconductor manufacturer specializing in energy-efficient silicon solutions for automotive, industrial, cloud, and IoT applications.

The MC74AC240MELG belongs to onsemi's legacy AC logic family, engineered for high-speed, low-power digital interfacing in industrial and computing infrastructure where reliability and wide voltage operation are essential.

FAQ

What logic family does the MC74AC240MELG belong to, and how does it differ from the MC74ACT240?

The MC74AC240MELG belongs to the Advanced CMOS (AC) logic family, characterized by CMOS input thresholds (VIH = 2.1 V @ 3.0 V VCC). Unlike the MC74ACT240, which features TTL-compatible inputs (VIH = 2.0 V @ 5.0 V), the MC74AC240MELG requires higher input voltage thresholds and is optimized for pure CMOS system integration - making it unsuitable for direct replacement in legacy TTL-driven circuits without level translation.

Does the MC74AC240MELG support operation at 3.3 V, and what are the guaranteed performance limits?

Yes, the MC74AC240MELG is fully specified for 3.3 V operation (VCC = 3.0–3.6 V). At 3.3 V, it guarantees VOH ≥ 2.9 V (IOH = −24 mA), VOL ≤ 0.44 V (IOL = 24 mA), and tPLH/tPHL ≤ 8.0 ns (CL = 50 pF), ensuring interoperability with standard 3.3 V LVTTL and CMOS interfaces without derating.

What is the function of the two separate output-enable inputs (OE1 and OE2) on the MC74AC240MELG?

The MC74AC240MELG features two independent active-low 3-state enables: OE1 controls outputs Y1–Y4 (pins 15, 17, 19, 20), and OE2 controls Y5–Y8 (pins 1, 2, 4, 6). This allows simultaneous or staggered disabling of two 4-bit bus segments - essential for memory banking, dual-peripheral arbitration, or reducing bus contention in multi-master systems.

Is the MC74AC240MELG pin-compatible with the SN74AC240N, and what are the mechanical implications?

Yes, the MC74AC240MELG and SN74AC240N share identical pin numbering and signal assignment. However, the MC74AC240MELG uses a SOIC-20W (case 751D) package (12.8 mm × 7.5 mm), while the SN74AC240N uses a PDIP-20 package (24.2 mm × 6.35 mm). PCB layout and thermal design must account for this dimensional and mounting difference - they are not drop-in replacements without board revision.

What is the maximum capacitive load the MC74AC240MELG can drive while maintaining specified timing performance?

The MC74AC240MELG is characterized for CL = 50 pF in its AC specifications, with tPLH/tPHL ≤ 7.0 ns at 5.0 V. While it can physically drive >50 pF loads, timing margins degrade linearly beyond this value - for loads exceeding 75 pF, designers should verify setup/hold timing in their specific layout or consider adding series termination or local buffering. The MC74AC240MELG's ±24 mA drive strength supports moderate trace capacitance but is not intended for heavy bus loading without verification.

MC74AC240MELG Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: 74AC

Package/Case:: 20-SOIC (0.209", 5.30mm Width)

Packaging:: Tape & Reel (TR)

Product Status:: Obsolete

Logic Type:: Buffer, Inverting

Number of Elements:: 2

Number of Bits per Element:: 4

Input Type:: -

Output Type:: 3-State

Current - Output High, Low:: 24mA, 24mA

Voltage - Supply:: 2V ~ 6V

Operating Temperature:: -40°C ~ 85°C (TA)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: SOEIAJ-20

MC74AC240MELG FAQ

1.How can I place an order for MC74AC240MELG through Aetrix?

Please submit a Request for Quotation (RFQ) for MC74AC240MELG 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 MC74AC240MELG reliable?

The price and inventory of MC74AC240MELG are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MC74AC240MELG is usually 5 days.

3.What payment methods are accepted for MC74AC240MELG?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MC74AC240MELG transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for MC74AC240MELG?

MC74AC240MELG orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your MC74AC240MELG 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 MC74AC240MELG?

For technical support, including MC74AC240MELG datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MC74AC240MELG requirements.

6.How does Aetrix verify that MC74AC240MELG is sourced from the original manufacturer or authorized distributors?

All MC74AC240MELG 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 MC74AC240MELG meets industry standards.

7.What is the process for return or replacement of MC74AC240MELG?

All MC74AC240MELG units undergo pre-shipment inspection (PSI). If there is an issue with MC74AC240MELG, 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 MC74AC240MELG part is unused and in its original packaging.

Return procedure for MC74AC240MELG:

1.Submit a request within 90 days.

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

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