74VHC123ASJX Equivalent & Substitute Parts

Part Overview

The 74VHC123ASJX is a monostable multivibrator logic IC manufactured by onsemi, featuring dual independent circuits with Schmitt trigger inputs and 8.1 ns propagation delay. The device is packaged in 16-SOP surface mount configuration and operates across a 2 V to 5.5 V supply range. This part is currently listed as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement.

Substiute Parts

74VHC123ASJX

onsemiIn Stock: 217874VHC123ASJX Datasheet

Current PartRFQ

74VHC123AMX

onsemiIn Stock: 375774VHC123AMX Datasheet

SimilarRFQ

SN74LV123ANSR

Texas InstrumentsIn Stock: 3241SN74LV123ANSR Datasheet

DirectRFQ

74AHC123AD,118

Nexperia USA Inc.In Stock: 681274AHC123AD,118 Datasheet

SimilarRFQ

SN74AHC123AD

Texas InstrumentsIn Stock: 1948SN74AHC123AD Datasheet

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SN74AHC123ADR

Texas InstrumentsIn Stock: 5508SN74AHC123ADR Datasheet

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SN74AHC123AMDREP

Texas InstrumentsIn Stock: 3309SN74AHC123AMDREP Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for the 74VHC123ASJX is determined by the following critical parameters:

Primary Compatibility Criteria:

• Logic type: Monostable multivibrator
• Independent circuits: 2
• Supply voltage range: 2 V ~ 5.5 V (minimum overlap required)
• Mounting type: Surface mount
• Package compatibility: 16-pin SOIC variants

Secondary Compatibility Factors:

• Propagation delay: Faster or equivalent performance acceptable
• Output current: Equal or greater drive capability acceptable
• Schmitt trigger input: Presence acceptable; absence requires application review
• Operating temperature range: Extended range acceptable; narrower range requires application verification
• Product status: Active or discontinued parts acceptable; obsolete status indicates end-of-life

Substitute parts are grouped into two categories: direct equivalents (identical base product number with different packaging) and functional alternatives (different series with compatible electrical characteristics).

Parameter Comparison

Engineering Selection Recommendations

Direct Equivalent (Preferred for Obsolete Part Replacement):

74VHC123AMX is the primary substitute for 74VHC123ASJX. Both parts share identical electrical specifications (8.1 ns propagation delay, 8 mA output current, Schmitt trigger inputs) and base product number (74VHC123). The 74VHC123AMX is currently active in production and available in higher inventory quantities (3700 pcs). The only difference is package width (3.90mm vs 5.30mm), which is compatible with standard 16-SOIC footprints. Packaging format differs (Tape & Reel vs Cut Tape), but this does not affect electrical performance.

Active Alternatives with Extended Temperature Range:

SN74AHC123ADR and SN74AHC123AMDREP are active Texas Instruments parts with faster propagation delay (7.5 ns vs 8.1 ns) and identical output current specifications. SN74AHC123AMDREP offers extended operating temperature range (-55°C ~ 125°C) compared to the original part (-40°C ~ 85°C), providing additional thermal margin for demanding applications. Both maintain Schmitt trigger input functionality and ROHS3 compliance.

Higher Performance Alternative:

74AHC123AD,118 from Nexperia provides the fastest propagation delay (5.1 ns) among available substitutes, with identical output current and supply voltage specifications. This part lacks Schmitt trigger inputs, which may affect noise immunity in applications relying on this feature. Extended operating temperature range (-40°C ~ 125°C) is available.

Extended Temperature Option:

SN74LV123ANSR from Texas Instruments offers the widest operating temperature range (-40°C ~ 125°C) and highest output current (12 mA), with package width matching the original part (5.30mm). Propagation delay is slower (13 ns), which is acceptable for timing-non-critical applications. All parts maintain ROHS3 compliance and unlimited moisture sensitivity level (MSL 1).

Frequently Asked Questions (FAQ)

Q: Can 74VHC123AMX directly replace 74VHC123ASJX on the same PCB?

A: Yes. Both parts use 16-SOIC package footprints with identical pin configurations and electrical specifications. The package width difference (3.90mm vs 5.30mm) is within standard SOIC tolerance and compatible with existing PCB layouts. Verify footprint dimensions with your PCB design files to confirm clearance.

Q: What is the difference between Cut Tape and Tape & Reel packaging?

A: Both are surface mount tape formats suitable for automated assembly. Cut Tape (CT) is supplied in shorter lengths for manual handling or small-volume production. Tape & Reel (TR) is supplied on continuous reels for high-volume automated pick-and-place equipment. Electrical performance is identical; packaging choice depends on production volume and assembly equipment.

Q: Why do some substitutes have different propagation delays?

A: Propagation delay varies by semiconductor series and manufacturing process. The 74VHC series (8.1 ns) uses a different process than 74AHC (5.1-7.5 ns) or 74LV (13 ns) series. Faster propagation delay is generally acceptable as a substitute if timing margins in your circuit allow. Verify maximum propagation delay specifications against your circuit timing requirements.

Q: Is Schmitt trigger input functionality critical for substitution?

A: Schmitt trigger inputs provide hysteresis for improved noise immunity on signal transitions. If your application relies on this feature for signal conditioning, select substitutes that include Schmitt trigger inputs (74VHC123AMX, SN74AHC123ADR, SN74AHC123AMDREP, SN74AHC123AD). The 74AHC123AD,118 lacks this feature and requires application-level evaluation.

Q: Can I use parts with extended temperature ranges in place of the original?

A: Yes. Extended operating temperature ranges (-55°C ~ 125°C or -40°C ~ 125°C) are backward compatible with the original specification (-40°C ~ 85°C). Use extended-range parts when your application requires operation beyond the original temperature limits or when additional thermal margin is desired.

Q: What does "Discontinued at DiGi Electronics" mean for SN74AHC123AD?

A: This indicates the part is no longer actively stocked by DiGi Electronics but may remain available through other distributors or as remaining inventory. For new designs, select active parts (74VHC123AMX, SN74AHC123ADR, SN74AHC123AMDREP) to ensure long-term supply availability.

Q: Are all substitute parts ROHS3 compliant?

A: Yes. All listed substitute parts maintain ROHS3 compliance and unlimited moisture sensitivity level (MSL 1), matching the original part's environmental and regulatory specifications.