74LCX138M Decoder/Demultiplexer Equivalent & Substitute Parts

Part Overview

The 74LCX138M is a 1 x 3:8 decoder/demultiplexer logic IC manufactured by onsemi in a 16-SOIC surface mount package. This part is classified as obsolete, which necessitates identification of equivalent and substitute components for ongoing design support and procurement. The 74LCX138M operates from a single 2V to 3.6V supply with 24mA output drive capability and is suitable for applications requiring address decoding and signal demultiplexing in low-voltage environments.

Key Parameters

Parameter	Value
Type	Decoder/Demultiplexer
Circuit Configuration	1 x 3:8
Output Current (High/Low)	24mA / 24mA
Supply Voltage Range	2V ~ 3.6V
Operating Temperature Range	-40°C ~ 85°C
Package Type	16-SOIC (0.154", 3.90mm Width)
Mounting Type	Surface Mount
RoHS Status	ROHS3 Compliant
Product Status	Obsolete

Substitute Part Grouping Explanation

Substitution of the 74LCX138M is determined by the following critical parameters:

Functional equivalence: 1 x 3:8 decoder/demultiplexer circuit configuration
Electrical compatibility: 24mA output drive current (high and low)
Supply voltage range: Minimum 2V operation required
Package compatibility: 16-SOIC surface mount package with 0.154" width
Temperature rating: -40°C minimum and 85°C minimum operating range
Compliance: ROHS3 compliance maintained

Substitute parts are categorized into two groups:

Direct Substitutes maintain identical specifications across all critical parameters and can be used as pin-for-pin replacements without design modification.

Similar Substitutes meet all functional and electrical requirements but may differ in supply voltage range extension, temperature rating extension, packaging format, or automotive qualification. These require design review to confirm compatibility with specific application requirements.

Parameter Comparison

Part Number	Manufacturer	Product Status	Supply Voltage	Temperature Range	Package	Output Current	RoHS Status	Automotive Grade
74LCX138M	onsemi	Obsolete	2V ~ 3.6V	-40°C ~ 85°C	16-SOIC (0.154")	24mA / 24mA	ROHS3	No
NLV74LCX138DR2G	onsemi	Obsolete	2V ~ 3.6V	-40°C ~ 85°C	16-SOIC (0.154")	24mA / 24mA	ROHS3	Yes (AEC-Q100)
SN74LVC138AD	Texas Instruments	Active	1.65V ~ 3.6V	-40°C ~ 85°C	16-SOIC (0.154")	24mA / 24mA	ROHS3	No
74LVC138AD,118	Nexperia USA Inc.	Active	1.2V ~ 3.6V	-40°C ~ 125°C	16-SOIC (0.154")	24mA / 24mA	ROHS3	No
SN74LVC138ADR	Texas Instruments	Active	1.65V ~ 3.6V	-40°C ~ 85°C	16-SOIC (0.154")	24mA / 24mA	ROHS3	No
SN74LVC138ADT	Texas Instruments	Active	1.65V ~ 3.6V	-40°C ~ 85°C	16-SOIC (0.154")	24mA / 24mA	ROHS3	No
SN74LVC138ANS	Texas Instruments	Active	1.65V ~ 3.6V	-40°C ~ 85°C	16-SOIC (0.209")	24mA / 24mA	Not applicable	No
SN74LVC138ANSR	Texas Instruments	Active	1.65V ~ 3.6V	-40°C ~ 85°C	16-SOIC (0.209")	24mA / 24mA	ROHS3	No
SN74LVC138AQDREP	Texas Instruments	Active	2V ~ 3.6V	-40°C ~ 125°C	16-SOIC (0.154")	24mA / 24mA	ROHS3	No
SN74LVC138AQDRG4Q1	Texas Instruments	Active	2V ~ 3.6V	-40°C ~ 125°C	16-SOIC (0.154")	24mA / 24mA	ROHS3	Yes (AEC-Q100)
SN74LVC138AQDRQ1	Texas Instruments	Active	2V ~ 3.6V	-40°C ~ 125°C	16-SOIC (0.154")	24mA / 24mA	ROHS3	Yes (AEC-Q100)

Engineering Selection Recommendations

For direct replacement without design modification:

NLV74LCX138DR2G from onsemi provides the closest functional match to the 74LCX138M, maintaining identical supply voltage range (2V ~ 3.6V) and temperature rating (-40°C ~ 85°C). This part adds automotive AEC-Q100 qualification, making it suitable for both commercial and automotive applications. Both parts are obsolete status, so long-term availability should be verified.

For active production designs requiring long-term availability:

SN74LVC138AQDRQ1 or SN74LVC138AQDRG4Q1 from Texas Instruments are recommended. Both are active status parts with identical supply voltage range (2V ~ 3.6V) and extended temperature rating (-40°C ~ 125°C). Both carry AEC-Q100 automotive qualification and ROHS3 compliance. These parts provide superior long-term availability and supply chain stability.

For applications with relaxed supply voltage requirements:

SN74LVC138AD, SN74LVC138ADR, or SN74LVC138ADT from Texas Instruments support lower minimum supply voltage (1.65V) while maintaining the required 3.6V maximum. These active status parts are suitable for low-power applications and offer excellent availability. Package width remains 0.154" for PCB compatibility.

For extended temperature applications:

74LVC138AD,118 from Nexperia USA Inc. extends the operating temperature range to -40°C ~ 125°C and supports the lowest minimum supply voltage (1.2V). This part is active status with ROHS3 compliance and represents the broadest operational envelope among available substitutes.

Package consideration:

SN74LVC138ANS and SN74LVC138ANSR feature a wider 16-SOIC package (0.209" width) compared to the standard 0.154" width. These parts require PCB layout verification before selection to ensure footprint compatibility.

Frequently Asked Questions (FAQ)

Q: Can I use SN74LVC138AD as a direct replacement for 74LCX138M?

A: Yes, with design review. SN74LVC138AD meets all functional requirements (1 x 3:8 decoder, 24mA output, 16-SOIC package). The supply voltage range is 1.65V ~ 3.6V, which encompasses the original 2V ~ 3.6V specification. Temperature rating (-40°C ~ 85°C) matches the original. Verify that your application does not require operation below 1.65V.

Q: What is the difference between NLV74LCX138DR2G and SN74LVC138AQDRQ1?

A: Both are functionally equivalent with identical supply voltage (2V ~ 3.6V) and extended temperature range (-40°C ~ 125°C). NLV74LCX138DR2G is from onsemi and is obsolete status. SN74LVC138AQDRQ1 is from Texas Instruments and is active status with superior long-term availability. Both carry AEC-Q100 automotive qualification.

Q: Why do some parts have different package widths (0.154" vs 0.209")?

A: Package width affects PCB footprint dimensions. The 0.154" width (SN74LVC138AD, SN74LVC138ADR, SN74LVC138ADT, SN74LVC138AQDREP, SN74LVC138AQDRG4Q1, SN74LVC138AQDRQ1) matches the original 74LCX138M footprint. The 0.209" width (SN74LVC138ANS, SN74LVC138ANSR) requires PCB layout modification. Verify package dimensions against your PCB design before selection.

Q: Is RoHS3 compliance maintained across all substitutes?

A: Most substitutes maintain ROHS3 compliance. SN74LVC138ANS shows "Not applicable" RoHS status; verify compliance requirements with your supply chain before selection. All other listed parts are ROHS3 compliant.

Q: Which substitute offers the best long-term availability?

A: SN74LVC138AQDRQ1 and SN74LVC138AQDRG4Q1 from Texas Instruments are active status parts with the highest inventory levels (4085 and 973 pcs respectively) and automotive qualification. These represent the most stable long-term supply options.

Q: Can I use parts with lower minimum supply voltage (1.65V or 1.2V) if my design operates at 2V?

A: Yes. Parts with lower minimum voltage specifications (SN74LVC138AD at 1.65V, 74LVC138AD,118 at 1.2V) are fully compatible with designs operating at 2V and above. The lower minimum rating provides additional design margin and flexibility for future applications.

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