FST3125QSCX Bus Switch 1 x 1:1 Equivalent & Substitute Parts

Part Overview

The FST3125QSCX is a logic bus switch IC manufactured by onsemi, configured as a 1 x 1:1 switch with 4 independent circuits in a 16-QSOP package. This component is classified as obsolete, making equivalent substitute parts necessary for new designs and ongoing production requirements. The FST3125QSCX operates with a single supply voltage range of 4V to 5.5V and supports operating temperatures from -40°C to 85°C in surface mount applications.

Substiute Parts

FST3125QSCX

onsemiIn Stock: 19464FST3125QSCX Datasheet

Current PartRFQ

SN74CBT3125DBQR

Texas InstrumentsIn Stock: 3870SN74CBT3125DBQR Datasheet

DirectRFQ

PI5C3125QE

Diodes IncorporatedIn Stock: 7405PI5C3125QE Datasheet

SimilarRFQ

PI5C3125QEX

Diodes IncorporatedIn Stock: 17979PI5C3125QEX Datasheet

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QS3125QG

Renesas Electronics CorporationIn Stock: 1392QS3125QG Datasheet

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QS3125QG8

Renesas Electronics CorporationIn Stock: 19276QS3125QG8 Datasheet

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SN74CBT3125CDBQR

Texas InstrumentsIn Stock: 806SN74CBT3125CDBQR Datasheet

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SN74CBTLV3125DBQR

Texas InstrumentsIn Stock: 2390SN74CBTLV3125DBQR Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitute parts for the FST3125QSCX are qualified based on the following electrical and mechanical parameters:

Critical Matching Parameters:

• Circuit configuration: 1 x 1:1 with 4 independent circuits
• Package type: 16-QSOP or 16-SSOP (0.154", 3.90mm Width)
• Operating temperature range: -40°C to 85°C
• Mounting type: Surface Mount
• Supply voltage compatibility: Parts must operate within or encompass the 4V to 5.5V range

Substitute Categories:

Direct Substitutes (Voltage Range 4.5V ~ 5.5V): SN74CBT3125DBQR and SN74CBT3125CDBQR from Texas Instruments, and PI5C3125QE and PI5C3125QEX from Diodes Incorporated. These parts maintain the same circuit configuration and package footprint with voltage supply ranges that overlap the FST3125QSCX operating window.

Active Alternatives (Voltage Range 4.75V ~ 5.25V): QS3125QG and QS3125QG8 from Renesas Electronics Corporation. These parts provide the same functional configuration with a narrower voltage specification window that remains compatible with standard 5V logic applications.

Extended Voltage Range Alternative: SN74CBTLV3125DBQR from Texas Instruments operates at 2.3V to 3.6V, providing functional equivalence for applications requiring lower supply voltages, though this represents a different voltage class.

Parameter Comparison

Engineering Selection Recommendations

For Standard 5V Logic Applications:

SN74CBT3125CDBQR is the preferred substitute. This part is currently active in production, ROHS3 compliant, and maintains full electrical compatibility with the FST3125QSCX within the 4.5V to 5.5V operating range. The 16-SSOP package is mechanically compatible with the original 16-QSOP footprint for surface mount applications.

QS3125QG and QS3125QG8 from Renesas Electronics Corporation are active alternatives with ROHS3 compliance and unlimited moisture sensitivity rating. These parts operate within a narrower voltage window (4.75V ~ 5.25V) suitable for standard 5V supply systems.

For Last-Time-Buy Scenarios:

PI5C3125QEX from Diodes Incorporated provides equivalent functionality with ROHS3 compliance and unlimited MSL rating. This part is available in tape and reel packaging and maintains the required electrical specifications.

For Lower Voltage Applications:

SN74CBTLV3125DBQR operates at 2.3V to 3.6V and is suitable only for applications requiring reduced supply voltages. This part is not compatible with standard 5V logic systems.

Frequently Asked Questions (FAQ)

Q: Can I use SN74CBT3125DBQR as a direct replacement for FST3125QSCX?

A: Yes, within electrical operating parameters. Both parts maintain 1 x 1:1 circuit configuration with 4 independent circuits and operate across overlapping voltage ranges (4.5V ~ 5.5V). The package footprint is compatible for surface mount assembly. However, SN74CBT3125DBQR is classified as Last Time Buy, while SN74CBT3125CDBQR is the active production equivalent.

Q: What is the difference between PI5C3125QE and PI5C3125QEX?

A: Both parts are manufactured by Diodes Incorporated with identical electrical specifications and circuit configuration. The primary difference is packaging: PI5C3125QE is supplied in tube packaging, while PI5C3125QEX is supplied in tape and reel format. Both maintain ROHS3 compliance and unlimited MSL rating.

Q: Are QS3125QG and QS3125QG8 interchangeable?

A: Yes. Both Renesas parts maintain identical electrical specifications, circuit configuration, and operating temperature range. The primary difference is packaging designation. Both are active products with ROHS3 compliance and unlimited MSL rating.

Q: Why does SN74CBTLV3125DBQR have a different voltage range?

A: The SN74CBTLV3125DBQR is a low-voltage variant designed for 2.3V to 3.6V supply systems. This part is not compatible with standard 5V logic applications and should only be selected for systems specifically requiring reduced supply voltages.

Q: What packaging considerations apply when substituting the FST3125QSCX?

A: The FST3125QSCX uses 16-QSOP packaging. Substitute parts use 16-SSOP packaging, which maintains the same 0.154" (3.90mm) width and pin pitch. Both packages are compatible with standard surface mount assembly processes and PCB layouts designed for 16-pin small outline packages.

Q: Which substitute part has the best long-term availability?

A: QS3125QG and QS3125QG8 from Renesas Electronics Corporation are classified as active products, indicating ongoing production and availability. SN74CBT3125CDBQR from Texas Instruments is also active. Parts classified as Last Time Buy (SN74CBT3125DBQR, PI5C3125QE, PI5C3125QEX) have limited remaining inventory and production windows.