74FST3125DTR2 Equivalent & Substitute Parts

Part Overview

The 74FST3125DTR2 is a bus switch logic IC manufactured by onsemi, configured as a 1 x 1:1 circuit with 4 independent circuits in a 14-TSSOP package. This component is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement. 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, suitable for surface mount applications requiring bus switching functionality.

Key Parameters

Parameter	Value
Manufacturer Part Number	74FST3125DTR2
Manufacturer	onsemi
Category	Logic
Type	Bus Switch
Circuit Configuration	1 x 1:1
Independent Circuits	4
Voltage Supply Source	Single Supply
Voltage - Supply Range	4V ~ 5.5V
Operating Temperature	-40°C ~ 85°C
Mounting Type	Surface Mount
Package / Case	14-TSSOP (0.173", 4.40mm Width)
Moisture Sensitivity Level (MSL)	1 (Unlimited)
Product Status	Obsolete
RoHS Status	RoHS non-compliant

Substitute Part Grouping Explanation

Substitution for the 74FST3125DTR2 is determined by the following critical parameters:

Electrical Compatibility:

Circuit configuration: 1 x 1:1 with 4 independent circuits
Voltage supply source: Single supply operation
Voltage supply range: 4V ~ 5.5V (or compatible subset)
Operating temperature range: -40°C ~ 85°C

Mechanical Compatibility:

Mounting type: Surface mount
Package type: 14-TSSOP or equivalent footprint (0.173", 4.40mm width)

Compliance Considerations:

RoHS status and REACH compliance affect long-term availability and regulatory requirements
Product status (active, last time buy, obsolete, discontinued) indicates supply continuity

Substitute parts are grouped into three categories based on these parameters: parametric equivalents, direct manufacturer alternatives, and similar variants with package or compliance differences.

Parameter Comparison

Parameter	74FST3125DTR2 (Main)	FST3125MTCX	SN74CBT3125PW	SN74CBT3125PWR	SN74CBT3125CPW	SN74CBT3125CPWR
Manufacturer	onsemi	onsemi	Texas Instruments	Texas Instruments	Texas Instruments	Texas Instruments
Type	Bus Switch	Bus Switch	Bus Switch	Bus Switch	Bus Switch	Bus Switch
Circuit Configuration	1 x 1:1	1 x 1:1	1 x 1:1	1 x 1:1	1 x 1:1	1 x 1:1
Independent Circuits	4	4	4	4	4	4
Voltage Supply Source	Single Supply	Single Supply	Single Supply	Single Supply	Single Supply	Single Supply
Voltage - Supply Range	4V ~ 5.5V	4V ~ 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
Package / Case	14-TSSOP	14-TSSOP	14-TSSOP	14-TSSOP	14-TSSOP	14-TSSOP
Mounting Type	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount
MSL	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)
Product Status	Obsolete	Obsolete	Last Time Buy	Last Time Buy	Active	Active
RoHS Status	RoHS non-compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

Parametric Equivalent (FST3125MTCX): FST3125MTCX from onsemi provides identical electrical and mechanical specifications to the 74FST3125DTR2, with the primary advantage of ROHS3 compliance and higher inventory availability (37,800 units). This part is classified as obsolete but offers the closest technical match. Selection is appropriate when maintaining the onsemi product line is preferred and RoHS compliance is required.

Direct Manufacturer Alternatives (SN74CBT3125 Series - Texas Instruments): The SN74CBT3125PW, SN74CBT3125PWR, SN74CBT3125CPW, and SN74CBT3125CPWR variants from Texas Instruments are functionally equivalent with identical circuit configuration and package footprint. These parts differ in packaging format (tube vs. cut tape vs. tape & reel) and product status. All are ROHS3 compliant. SN74CBT3125CPW and SN74CBT3125CPWR are active products, providing the longest supply continuity. The voltage supply range for Texas Instruments variants is 4.5V ~ 5.5V, which is a subset of the original 4V ~ 5.5V specification; this is acceptable for applications operating within the 4.5V ~ 5.5V window.

Similar Variants with Package Differences (SN74CBT3125CDBR, SN74CBT3125DBR, SN74CBT3125DBRE4): These variants use 14-SSOP packaging (0.209", 5.30mm width) instead of 14-TSSOP. While electrically equivalent, the different package footprint requires PCB layout modification. SN74CBT3125CDBR is an active product with substantial inventory (29,100 units), making it suitable for new designs where package change is acceptable.

Alternative Package Format (SN74CBT3125DGVR): This variant uses 14-TVSOP packaging, differing from the original 14-TSSOP. Electrical specifications remain equivalent. This option is classified as last time buy with 3,300 units available.

Frequently Asked Questions (FAQ)

Q: Can I use SN74CBT3125 series parts as direct replacements for 74FST3125DTR2?

A: Yes, the SN74CBT3125 series from Texas Instruments is electrically and mechanically compatible when the voltage supply range of 4.5V ~ 5.5V meets your application requirements. The 14-TSSOP package variants (SN74CBT3125PW, SN74CBT3125PWR, SN74CBT3125CPW, SN74CBT3125CPWR) provide identical footprints. Packaging format differences (tube, cut tape, tape & reel) do not affect electrical performance.

Q: What is the difference between FST3125MTCX and SN74CBT3125 variants?

A: FST3125MTCX is manufactured by onsemi and maintains the original 4V ~ 5.5V voltage supply range. SN74CBT3125 variants are manufactured by Texas Instruments with a narrower 4.5V ~ 5.5V range. Both are ROHS3 compliant and functionally equivalent. Selection depends on manufacturer preference and voltage supply requirements.

Q: Can I use 14-SSOP package variants like SN74CBT3125CDBR instead of 14-TSSOP?

A: 14-SSOP and 14-TSSOP packages have different footprints (5.30mm vs. 4.40mm width). Electrical functionality is identical, but PCB layout modification is required. Use 14-SSOP variants only if your design can accommodate the larger package footprint.

Q: Why is the 74FST3125DTR2 marked as obsolete?

A: Obsolete status indicates the manufacturer has discontinued production. Equivalent parts from onsemi (FST3125MTCX) and Texas Instruments (SN74CBT3125 series) provide continued access to this functionality. Active product variants like SN74CBT3125CPW and SN74CBT3125CPWR are recommended for new designs requiring long-term supply assurance.

Q: Are all substitute parts RoHS compliant?

A: The original 74FST3125DTR2 is RoHS non-compliant. All recommended substitute parts (FST3125MTCX and SN74CBT3125 series) are ROHS3 compliant, meeting current regulatory requirements for new designs and procurement.

Q: What packaging options are available for the SN74CBT3125?

A: Texas Instruments offers SN74CBT3125 in multiple packaging formats: tube (PW suffix), cut tape (PWR suffix), and tape & reel (CPWR suffix). All maintain the same electrical specifications and 14-TSSOP footprint. Selection depends on procurement volume and handling requirements.

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