FSTU3257QSCX Equivalent & Substitute Parts

Part Overview

The FSTU3257QSCX is a 4 x 2:1 Multiplexer/Demultiplexer logic IC manufactured by onsemi in a 16-QSOP surface mount package. This component is classified as obsolete, making identification of functionally equivalent alternatives essential for ongoing design support and production continuity. The part operates across a single supply voltage range of 4V to 5.5V with an operating temperature range of -40°C to 85°C, serving applications requiring signal routing and multiplexing functionality in logic circuits.

Key Parameters

Parameter	Value
Manufacturer Part Number	FSTU3257QSCX
Manufacturer	onsemi
Category	Logic
Type	Multiplexer/Demultiplexer
Circuit Configuration	4 x 2:1
Independent Circuits	1
Voltage Supply	4V ~ 5.5V
Operating Temperature	-40°C ~ 85°C
Mounting Type	Surface Mount
Package / Case	16-LSSOP (0.154", 3.90mm Width)
Product Status	Obsolete
Moisture Sensitivity Level	1 (Unlimited)
REACH Status	REACH Unaffected

Substitute Part Grouping Explanation

Substitution of the FSTU3257QSCX is determined by the following critical parameters:

Functional Equivalence: All substitute parts maintain the identical 4 x 2:1 multiplexer/demultiplexer circuit configuration with a single independent circuit, ensuring pin-compatible functionality.

Electrical Compatibility: Substitute parts operate within the same voltage supply range (4.5V ~ 5.5V for active alternatives, which encompasses the original 4V ~ 5.5V specification) and maintain the identical operating temperature range of -40°C to 85°C.

Mounting and Package Considerations: Substitutes are available in two package variants—16-SSOP and 16-TSSOP—both surface mount options with 0.154" to 0.173" widths. These packages are mechanically compatible with the original 16-LSSOP footprint for board-level integration.

Product Status and Compliance: Active substitute parts from Texas Instruments and Nexperia USA Inc. provide ongoing availability and support, with RoHS3 compliance and REACH unaffected status matching the original part's regulatory standing.

Parameter Comparison

Parameter	FSTU3257QSCX (onsemi)	SN74CBT3257CDBQR (TI)	CBT3257ADS,118 (Nexperia)	CBT3257APW,118 (Nexperia)
Category	Logic	Logic	Logic	Logic
Type	Multiplexer/Demultiplexer	Multiplexer/Demultiplexer	Multiplexer/Demultiplexer	Multiplexer/Demultiplexer
Circuit Configuration	4 x 2:1	4 x 2:1	4 x 2:1	4 x 2:1
Independent Circuits	1	1	1	1
Voltage Supply	4V ~ 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
Mounting Type	Surface Mount	Surface Mount	Surface Mount	Surface Mount
Package / Case	16-LSSOP (0.154", 3.90mm)	16-SSOP (0.154", 3.90mm)	16-SSOP (0.154", 3.90mm)	16-TSSOP (0.173", 4.40mm)
Product Status	Obsolete	Active	Active	Active
RoHS Status	Not specified	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Moisture Sensitivity Level	1 (Unlimited)	2 (1 Year)	1 (Unlimited)	1 (Unlimited)
REACH Status	REACH Unaffected	REACH Unaffected	REACH Unaffected	REACH Unaffected

Engineering Selection Recommendations

Primary Substitute - SN74CBT3257CDBQR (Texas Instruments): This part provides direct functional equivalence with active product status and ROHS3 compliance. The 16-SSOP package maintains the same 0.154" width as the original FSTU3257QSCX, enabling straightforward PCB layout compatibility. Voltage supply range of 4.5V to 5.5V is compatible with designs operating within this window.

Alternative Substitutes - CBT3257ADS,118 and CBT3257APW,118 (Nexperia USA Inc.): Both Nexperia parts offer active product status with ROHS3 compliance and unlimited moisture sensitivity rating. CBT3257ADS,118 maintains the 16-SSOP package format identical to the Texas Instruments option. CBT3257APW,118 uses a 16-TSSOP package with slightly larger 0.173" width, requiring PCB footprint verification before implementation.

Compliance Alignment: All active substitutes maintain REACH unaffected status consistent with the original part, supporting regulatory continuity in applications subject to environmental compliance requirements.

Frequently Asked Questions (FAQ)

Q: Can the SN74CBT3257CDBQR directly replace the FSTU3257QSCX on existing PCBs?

A: The SN74CBT3257CDBQR maintains identical pin configuration and package width (0.154", 3.90mm) as the original FSTU3257QSCX. Both use 16-pin surface mount packages with equivalent electrical specifications, supporting direct PCB substitution without layout modification.

Q: What is the difference between the 16-SSOP and 16-TSSOP packages?

A: The 16-SSOP package (used by SN74CBT3257CDBQR and CBT3257ADS,118) has a 0.154" width, while the 16-TSSOP package (CBT3257APW,118) has a 0.173" width. Both are surface mount options, but the TSSOP variant requires verification of PCB footprint compatibility before selection.

Q: Are all substitute parts RoHS compliant?

A: Yes. The SN74CBT3257CDBQR, CBT3257ADS,118, and CBT3257APW,118 are all ROHS3 compliant, meeting current environmental and material restriction standards.

Q: What is the moisture sensitivity difference between the original and substitute parts?

A: The FSTU3257QSCX has MSL 1 (unlimited), while the SN74CBT3257CDBQR has MSL 2 (1 year). The Nexperia alternatives (CBT3257ADS,118 and CBT3257APW,118) both have MSL 1 (unlimited), matching the original specification.

Q: Do all substitutes operate at the same voltage range as the original?

A: The FSTU3257QSCX operates at 4V to 5.5V, while all active substitutes operate at 4.5V to 5.5V. Designs operating at 4V to 4.5V require the original part or equivalent with extended lower voltage specification.

Q: What is the inventory status of these substitute parts?

A: SN74CBT3257CDBQR has 2420 units in stock, CBT3257ADS,118 has 1900 units, and CBT3257APW,118 has 3127 units available as new original stock.

Request Quote (Ships tomorrow)

Part Number

Quantity

Company

Contact Name

E-mail

Message