74FST3861QSR Bus Switch Equivalent & Substitute Parts

Part Overview

The 74FST3861QSR is a 10 x 1:1 bus switch logic IC manufactured by onsemi in a 24-QSOP package. This component is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and production continuity. The 74FST3861QSR operates with a single supply voltage between 4V and 5.5V and supports operating temperatures from -40°C to 85°C in surface mount applications.

Substiute Parts

74FST3861QSR

onsemiIn Stock: 87174FST3861QSR Datasheet

Current PartRFQ

SN74CBT3861DBQR

Texas InstrumentsIn Stock: 4124SN74CBT3861DBQR Datasheet

DirectRFQ

PI5C3861QE

Diodes IncorporatedIn Stock: 1804PI5C3861QE Datasheet

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PI5C3861QEX

Diodes IncorporatedIn Stock: 2192PI5C3861QEX Datasheet

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SN74CBT3861PWR

Texas InstrumentsIn Stock: 5433SN74CBT3861PWR Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution for the 74FST3861QSR is determined by the following critical parameters:

• Circuit Configuration: All substitute parts must maintain 10 x 1:1 bus switch topology
• Voltage Supply Source: Single supply operation required
• Operating Temperature Range: -40°C to 85°C minimum
• Mounting Type: Surface mount only
• Package Compatibility: 24-pin SSOP/QSOP package family with 0.154" (3.90mm) width tolerance

Substitute parts are grouped into two categories: direct equivalents with identical package specifications (24-SSOP/QSOP) and functional equivalents with compatible but different package variants (24-TSSOP).

Parameter Comparison

Engineering Selection Recommendations

Direct Package Equivalents (24-SSOP/QSOP)

SN74CBT3861DBQR, PI5C3861QE, and PI5C3861QEX are functionally equivalent to the 74FST3861QSR with identical package dimensions. All three maintain the 10 x 1:1 bus switch configuration and -40°C to 85°C operating temperature range. SN74CBT3861DBQR and PI5C3861QEX offer ROHS3 compliance and improved supply voltage tolerance (4.5V ~ 5.5V and 4.75V ~ 5.25V respectively). PI5C3861QE and PI5C3861QEX feature unlimited moisture sensitivity (MSL 1), eliminating storage constraints.

Alternative Package Option (24-TSSOP)

SN74CBT3861PWR provides active product status and ROHS3 compliance with a 24-TSSOP package (0.173", 4.40mm width). This variant requires PCB layout modification due to increased package width but offers the longest supply availability and unlimited moisture sensitivity.

Compliance Considerations

The 74FST3861QSR is RoHS non-compliant. All substitute parts listed are ROHS3 compliant, supporting modern manufacturing and environmental standards. For applications requiring RoHS compliance, any of the four substitute parts are suitable. For applications with existing RoHS non-compliant designs, SN74CBT3861DBQR, PI5C3861QE, and PI5C3861QEX maintain backward compatibility while providing compliance upgrades.

Frequently Asked Questions (FAQ)

Q: Can SN74CBT3861PWR replace the 74FST3861QSR directly on the PCB?

A: SN74CBT3861PWR uses a 24-TSSOP package with 0.173" width versus the 0.154" width of the original 24-SSOP package. Direct footprint replacement is not possible without PCB layout modification. SN74CBT3861DBQR, PI5C3861QE, or PI5C3861QEX are recommended for direct substitution.

Q: What is the voltage compatibility range for substitutes?

A: The 74FST3861QSR operates at 4V ~ 5.5V. SN74CBT3861DBQR and SN74CBT3861PWR support 4.5V ~ 5.5V. PI5C3861QE and PI5C3861QEX support 4.75V ~ 5.25V. All substitutes are compatible with standard 5V supply designs. Applications requiring operation below 4.5V should verify compatibility with specific substitute selection.

Q: Are there moisture sensitivity differences between substitutes?

A: The 74FST3861QSR has MSL 1 (unlimited storage). SN74CBT3861DBQR has MSL 2 (1 year storage limit). PI5C3861QE, PI5C3861QEX, and SN74CBT3861PWR all have MSL 1 (unlimited storage). For applications with extended storage requirements, PI5C3861QE, PI5C3861QEX, or SN74CBT3861PWR are preferred.

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

A: SN74CBT3861PWR has active product status, indicating ongoing production and supply. SN74CBT3861DBQR, PI5C3861QE, and PI5C3861QEX are classified as Last Time Buy, indicating limited future availability. For new designs requiring extended production support, SN74CBT3861PWR is recommended despite package differences.

Q: Do all substitutes maintain the same circuit configuration?

A: Yes. All substitute parts maintain the 10 x 1:1 bus switch topology with single independent circuit, identical to the 74FST3861QSR. Functional behavior and pin configuration are equivalent across all listed substitutes.