FSTU3384QSCX Bus Switch 5 x 1:1 Equivalent & Substitute Parts

Part Overview

The FSTU3384QSCX is a bus switch logic IC manufactured by onsemi, configured as a 5 x 1:1 multiplexer in a 24-QSOP package. This component is classified as obsolete, making equivalent substitute parts necessary for new designs and ongoing production requirements. The part operates as a single-supply bus switch with voltage range 4V to 5.5V and temperature range -40°C to 85°C. Texas Instruments offers multiple active alternatives within the 74CBT and 74CBTD series that maintain functional and electrical compatibility.

Key Parameters

Parameter	Value
Manufacturer	onsemi
Part Number	FSTU3384QSCX
Type	Bus Switch
Circuit Configuration	5 x 1:1
Independent Circuits	2
Voltage Supply	Single Supply, 4V ~ 5.5V
Operating Temperature	-40°C ~ 85°C
Package Type	24-QSOP (0.154", 3.90mm Width)
Mounting Type	Surface Mount
Product Status	Obsolete
Moisture Sensitivity Level	1 (Unlimited)

Substitute Part Grouping Explanation

Substitution of the FSTU3384QSCX is determined by the following critical parameters:

Functional Equivalence: All substitute parts maintain the 5 x 1:1 bus switch configuration with 2 independent circuits, ensuring identical signal routing and multiplexing capability.

Electrical Compatibility: All substitutes operate on single supply voltage with 4.5V to 5.5V range (note: FSTU3384QSCX operates 4V to 5.5V, while all Texas Instruments substitutes operate 4.5V to 5.5V). Operating temperature range remains -40°C to 85°C across all parts.

Package Compatibility: Substitutes are grouped by package type—24-SSOP, 24-TVSOP, and 24-TSSOP—each with different physical dimensions but identical pin counts and surface mount mounting type.

Series Variants: Texas Instruments offers two series—74CBT and 74CBTD—both functionally equivalent for this application. The 74CBTD series includes additional features but maintains backward compatibility.

Product Status: All Texas Instruments substitutes are active products with RoHS3 compliance, addressing the obsolescence of the original onsemi part.

Parameter Comparison

Parameter	FSTU3384QSCX (onsemi)	SN74CBT3384CDBQR (TI)	SN74CBT3384CDGVR (TI)	SN74CBT3384CPW (TI)	SN74CBT3384CPWR (TI)	SN74CBTD3384CDBQR (TI)	SN74CBTD3384CDBR (TI)	SN74CBTD3384CDGVR (TI)	SN74CBTD3384CPW (TI)	SN74CBTD3384CPWR (TI)
Type	Bus Switch	Bus Switch	Bus Switch	Bus Switch	Bus Switch	Bus Switch	Bus Switch	Bus Switch	Bus Switch	Bus Switch
Circuit Configuration	5 x 1:1	5 x 1:1	5 x 1:1	5 x 1:1	5 x 1:1	5 x 1:1	5 x 1:1	5 x 1:1	5 x 1:1	5 x 1:1
Independent Circuits	2	2	2	2	2	2	2	2	2	2
Voltage Supply Range	4V ~ 5.5V	4.5V ~ 5.5V	4.5V ~ 5.5V	4.5V ~ 5.5V	4.5V ~ 5.5V	4.5V ~ 5.5V	4.5V ~ 5.5V	4.5V ~ 5.5V	4.5V ~ 5.5V	4.5V ~ 5.5V
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	-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	Surface Mount	Surface Mount	Surface Mount	Surface Mount
Package Type	24-QSOP	24-SSOP	24-TVSOP	24-TSSOP	24-TSSOP	24-SSOP	24-SSOP	24-TVSOP	24-TSSOP	24-TSSOP
Package Width	0.154" (3.90mm)	0.154" (3.90mm)	0.173" (4.40mm)	0.173" (4.40mm)	0.173" (4.40mm)	0.154" (3.90mm)	0.209" (5.30mm)	0.173" (4.40mm)	0.173" (4.40mm)	0.173" (4.40mm)
Product Status	Obsolete	Active	Active	Active	Active	Active	Active	Active	Active	Active
RoHS Status	Not specified	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Moisture Sensitivity Level	1 (Unlimited)	2 (1 Year)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	2 (1 Year)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)

Engineering Selection Recommendations

For Direct Package Replacement (24-SSOP): Select SN74CBT3384CDBQR or SN74CBTD3384CDBQR. Both maintain the 0.154" (3.90mm) width matching the original FSTU3384QSCX footprint. SN74CBTD3384CDBQR offers MSL 2 (1 Year) sensitivity, while SN74CBT3384CDBQR provides the same specification. Both are active products with ROHS3 compliance.

For Compact Footprint (24-TVSOP): Select SN74CBT3384CDGVR or SN74CBTD3384CDGVR. These parts use 0.173" (4.40mm) width packages, suitable for space-constrained designs. Both maintain MSL 1 (Unlimited) rating and ROHS3 compliance.

For Tape & Reel Packaging: SN74CBT3384CPWR and SN74CBTD3384CPWR are available in 24-TSSOP with Tape & Reel packaging, supporting high-volume production requirements. Both offer MSL 1 (Unlimited) and ROHS3 compliance.

Series Selection: The 74CBT series provides baseline functionality. The 74CBTD series offers enhanced features while maintaining full backward compatibility. Selection between series depends on application-specific requirements beyond the scope of this substitution analysis.

Voltage Consideration: All Texas Instruments substitutes operate at 4.5V minimum, compared to the FSTU3384QSCX at 4V minimum. Verify system supply voltage meets the 4.5V to 5.5V range for seamless substitution.

Frequently Asked Questions (FAQ)

Q: Can I use any of these substitutes as a direct replacement for FSTU3384QSCX?

A: Functionally, yes. All substitutes maintain the 5 x 1:1 bus switch configuration, 2 independent circuits, and -40°C to 85°C operating temperature. However, package type and voltage minimum differ. For PCB layout compatibility, select a substitute matching your original package type or verify PCB redesign feasibility.

Q: What is the difference between 24-QSOP, 24-SSOP, 24-TVSOP, and 24-TSSOP packages?

A: These are distinct surface mount package types with different physical dimensions. 24-QSOP (original) is 0.154" wide. 24-SSOP substitutes are also 0.154" wide, providing direct footprint compatibility. 24-TVSOP and 24-TSSOP are 0.173" wide, requiring PCB layout modification. Package selection depends on available board space and manufacturing capabilities.

Q: Why do Texas Instruments substitutes specify 4.5V minimum instead of 4V?

A: This reflects the electrical specifications of the 74CBT and 74CBTD series. If your system operates below 4.5V, the FSTU3384QSCX cannot be substituted with these parts. Verify your supply voltage range before selection.

Q: What does MSL (Moisture Sensitivity Level) mean for my application?

A: MSL indicates how long a component can be stored after moisture absorption before soldering. MSL 1 (Unlimited) allows indefinite storage. MSL 2 (1 Year) requires soldering within one year of package opening. For long-term inventory, prefer MSL 1 rated parts.

Q: Are all substitutes RoHS3 compliant?

A: Yes. All Texas Instruments substitutes listed are ROHS3 compliant, meeting environmental and regulatory requirements. The original FSTU3384QSCX does not specify RoHS status.

Q: Can I mix different package types in the same design?

A: No. Each package type has distinct physical dimensions and PCB footprints. Select one package type for your design and maintain consistency across production runs.

Q: What is the difference between 74CBT and 74CBTD series?

A: Both series provide 5 x 1:1 bus switch functionality with identical pin counts and electrical specifications for this application. The 74CBTD series includes additional features. Both are functionally equivalent for substitution purposes.

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