74AC240SJ Equivalent & Substitute Parts

Part Overview

The 74AC240SJ is a Buffer, Inverting logic IC manufactured by onsemi, featuring 2 elements with 4 bits per element and 3-state output capability. This component operates across a 2V to 6V supply voltage range with 24mA output current capacity and supports operating temperatures from -40°C to 85°C. The part is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement.

Key Parameters

Parameter	Value
Manufacturer Part Number	74AC240SJ
Manufacturer	onsemi
Logic Type	Buffer, Inverting
Number of Elements	2
Number of Bits per Element	4
Output Type	3-State
Current - Output High, Low	24mA, 24mA
Voltage - Supply	2V ~ 6V
Operating Temperature	-40°C ~ 85°C (TA)
Mounting Type	Surface Mount
Package / Case	20-SOIC (0.209", 5.30mm Width)
Product Status	Obsolete

Substitute Part Grouping Explanation

Substitution for the 74AC240SJ is determined by the following critical parameters:

Logic Type: Buffer, Inverting (2 elements, 4 bits per element)
Output Type: 3-State
Output Current: 24mA minimum (High and Low)
Supply Voltage Range: Must encompass or match 2V ~ 6V
Operating Temperature: -40°C ~ 85°C
Mounting Type: Surface Mount
Package Compatibility: 20-SOIC or 20-SO variants

Substitute parts are grouped by package type and electrical performance. Parts with identical electrical specifications and compatible packages are direct substitutes. Parts with higher output current ratings or extended voltage ranges remain functionally compatible within the 74AC240SJ operating envelope.

Parameter Comparison

Parameter	74AC240SJ (onsemi)	CD74AC240M (Harris)	CD74AC240M96 (TI)	SN74AC240DW (TI)	SN74AC240DWR (TI)	SN74AC240NSR (TI)
Logic Type	Buffer, Inverting	Buffer, Inverting	Buffer, Inverting	Buffer, Inverting	Buffer, Inverting	Buffer, Inverting
Number of Elements	2	2	2	2	2	2
Number of Bits per Element	4	4	4	4	4	4
Output Type	3-State	3-State	3-State	3-State	3-State	3-State
Current - Output High, Low	24mA, 24mA	50mA, 50mA	24mA, 24mA	24mA, 24mA	24mA, 24mA	24mA, 24mA
Voltage - Supply	2V ~ 6V	1.5V ~ 5.5V	1.5V ~ 5.5V	2V ~ 6V	2V ~ 6V	2V ~ 6V
Operating Temperature	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C
Mounting Type	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount
Package / Case	20-SOIC (0.209", 5.30mm)	20-SOIC (0.295", 7.50mm)	20-SOIC (0.295", 7.50mm)	20-SOIC (0.295", 7.50mm)	20-SOIC (0.295", 7.50mm)	20-SO (0.209", 5.30mm)
Product Status	Obsolete	Obsolete	Active	Discontinued at DiGi Electronics	Active	Active
RoHS Status	Not specified	RoHS non-compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

Direct Substitutes (Identical Package and Electrical Specifications):

SN74AC240NSR is the primary direct substitute for 74AC240SJ. Both parts share the 20-SO package (0.209", 5.30mm width), identical output current ratings (24mA), matching supply voltage range (2V ~ 6V), and equivalent operating temperature specifications. SN74AC240NSR holds Active product status with ROHS3 compliance and unlimited moisture sensitivity level.

Compatible Substitutes (Electrical Equivalence with Package Variation):

SN74AC240DWR and SN74AC240DW are functionally equivalent alternatives with identical electrical specifications but feature the wider 20-SOIC package (0.295", 7.50mm). SN74AC240DWR is Active status with ROHS3 compliance. SN74AC240DW is discontinued at DiGi Electronics but remains available in inventory. Both support the full 2V ~ 6V supply range and 24mA output current.

CD74AC240M96 provides functional compatibility with Active product status and ROHS3 compliance. This part operates within a 1.5V ~ 5.5V supply range, which encompasses the 74AC240SJ operating envelope. The 20-SOIC package (0.295", 7.50mm) requires PCB layout verification for mechanical fit.

Alternative with Enhanced Output Current:

CD74AC240M (Harris Corporation) offers 50mA output current capability, exceeding the 74AC240SJ specification. This part operates within 1.5V ~ 5.5V supply range and is classified as obsolete with RoHS non-compliance. The enhanced current rating provides design margin for applications requiring higher drive capability.

Frequently Asked Questions (FAQ)

Q: Can SN74AC240NSR directly replace 74AC240SJ without PCB modification?

A: Yes. SN74AC240NSR shares the identical 20-SO package footprint (0.209", 5.30mm width) and electrical specifications with 74AC240SJ, enabling direct substitution without PCB layout changes.

Q: What is the difference between 20-SO and 20-SOIC packages?

A: The 20-SO package measures 0.209" in width, while 20-SOIC measures 0.295" in width. Both are surface-mount packages with 20 pins. PCB footprints are not interchangeable; parts must match the existing pad layout.

Q: Are the Texas Instruments parts (SN74AC240DWR, SN74AC240DW, SN74AC240NSR) fully compatible with 74AC240SJ?

A: All three Texas Instruments parts are functionally equivalent. SN74AC240NSR matches the package footprint exactly. SN74AC240DWR and SN74AC240DW require package footprint verification due to the wider 20-SOIC case, but electrical performance is identical.

Q: Why does CD74AC240M have higher output current (50mA vs 24mA)?

A: CD74AC240M is rated for 50mA output current, which exceeds the 74AC240SJ specification of 24mA. This part remains functionally compatible as it meets or exceeds all electrical requirements within the operating envelope.

Q: What is the significance of RoHS compliance status?

A: ROHS3-compliant parts (SN74AC240DWR, SN74AC240DW, CD74AC240M96, SN74AC240NSR) meet current environmental regulations. CD74AC240M is RoHS non-compliant and may face procurement restrictions in regulated applications.

Q: Which substitute part has the best availability and compliance profile?

A: SN74AC240DWR combines Active product status, ROHS3 compliance, and current inventory availability. SN74AC240NSR is the preferred direct footprint replacement with identical package dimensions.

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