FST3125M Equivalent & Substitute Parts

Part Overview

The FST3125M is a 1 x 1:1 bus switch logic IC manufactured by onsemi in a 14-SOIC surface mount package. This component functions as a single-channel bus switch with 4 independent circuits, designed for signal routing and isolation applications in digital systems. The FST3125M carries an obsolete product status, making identification of functionally equivalent alternatives essential for ongoing design support and component procurement.

Key Parameters

Parameter	FST3125M
Manufacturer	onsemi
Type	Bus Switch
Circuit Configuration	1 x 1:1
Independent Circuits	4
Package / Case	14-SOIC (0.154", 3.90mm Width)
Mounting Type	Surface Mount
Voltage Supply	4V ~ 5.5V
Operating Temperature	-40°C ~ 85°C
Product Status	Obsolete
Moisture Sensitivity Level	1 (Unlimited)

Substitute Part Grouping Explanation

Substitution eligibility for the FST3125M is determined by the following critical parameters:

Mandatory Compatibility Criteria:

Circuit configuration: 1 x 1:1 topology with 4 independent circuits
Package type: 14-SOIC form factor (0.154", 3.90mm Width)
Mounting method: Surface mount
Voltage supply architecture: Single supply operation

Acceptable Parameter Variations:

Voltage supply range: Minimum 4V operation required; ranges extending above 5.5V are acceptable
Operating temperature range: Minimum -40°C to 85°C required; extended ranges are acceptable
Manufacturer: Multiple qualified sources available
Product status: Active or Last Time Buy status preferred over obsolete
Packaging format: Tube, Cut Tape, or Tape & Reel formats are interchangeable for the same part number

Substitutes are grouped into three categories: Upgrade (enhanced specifications), Direct (equivalent specifications), and Similar (compatible with noted parameter differences).

Parameter Comparison

Part Number	Manufacturer	Circuit Config	Package	Voltage Supply	Temp Range	Product Status	RoHS Status
FST3125M	onsemi	1 x 1:1	14-SOIC	4V ~ 5.5V	-40°C ~ 85°C	Obsolete	Not specified
FST3125DR2G	onsemi	1 x 1:1	14-SOIC	4V ~ 5.5V	-55°C ~ 125°C	Obsolete	ROHS3 Compliant
SN74CBT3125D	Texas Instruments	1 x 1:1	14-SOIC	4.5V ~ 5.5V	-40°C ~ 85°C	Last Time Buy	ROHS3 Compliant
SN74CBT3125DR	Texas Instruments	1 x 1:1	14-SOIC	4.5V ~ 5.5V	-40°C ~ 85°C	Last Time Buy	ROHS3 Compliant
SN74CBT3125CD	Texas Instruments	1 x 1:1	14-SOIC	4.5V ~ 5.5V	-40°C ~ 85°C	Active	ROHS3 Compliant
SN74CBT3125CDR	Texas Instruments	1 x 1:1	14-SOIC	4.5V ~ 5.5V	-40°C ~ 85°C	Active	ROHS3 Compliant
SN74CBTLV3125D	Texas Instruments	1 x 1:1	14-SOIC	2.3V ~ 3.6V	-40°C ~ 85°C	Last Time Buy	ROHS3 Compliant

Engineering Selection Recommendations

Upgrade Path: FST3125DR2G (onsemi) provides extended operating temperature range (-55°C to 125°C) while maintaining the original voltage supply specification and package form factor. This part carries ROHS3 compliance certification and represents an enhanced specification variant suitable for applications requiring wider temperature operation.

Direct Equivalents: SN74CBT3125D and SN74CBT3125DR (Texas Instruments) maintain functional equivalence with identical circuit configuration, package type, and operating temperature range. Both parts carry Active or Last Time Buy status with ROHS3 compliance. The voltage supply minimum is specified at 4.5V rather than 4V, which is acceptable for standard 5V logic applications.

Active Production Alternatives: SN74CBT3125CD and SN74CBT3125CDR (Texas Instruments) are currently in Active production status, offering long-term availability and supply chain stability. These parts are functionally equivalent to the FST3125M with identical electrical specifications and package requirements.

Low-Voltage Variant: SN74CBTLV3125D (Texas Instruments) operates at reduced voltage levels (2.3V to 3.6V) and is suitable only for applications designed for low-voltage logic operation. This part is not a direct substitute for standard 5V applications but serves as an alternative for low-voltage system designs.

Frequently Asked Questions (FAQ)

Q: Can FST3125DR2G replace FST3125M in all applications? FST3125DR2G is functionally compatible with FST3125M for standard operating conditions. The extended temperature range (-55°C to 125°C) provides additional capability beyond the original -40°C to 85°C specification. Applications operating within the original temperature range experience no functional difference.

Q: What is the difference between SN74CBT3125D, SN74CBT3125DR, SN74CBT3125CD, and SN74CBT3125CDR? These four Texas Instruments part numbers share identical electrical specifications and circuit configuration. The differences are packaging format and product status: D variants use Tube packaging, DR variants use Tape & Reel packaging, and CD/CDR variants represent the same distinction with Active production status. Selection depends on procurement requirements and packaging preferences.

Q: Is SN74CBTLV3125D a suitable replacement for FST3125M? SN74CBTLV3125D is not suitable for direct replacement in 5V logic systems. This part operates at 2.3V to 3.6V supply voltage and is designed for low-voltage applications. Use only when system design specifically requires low-voltage operation.

Q: Are all substitute parts available in 14-SOIC package? All listed substitute parts are manufactured in 14-SOIC (0.154", 3.90mm Width) surface mount package, maintaining mechanical and electrical compatibility with FST3125M PCB layouts.

Q: What compliance certifications apply to substitute parts? All Texas Instruments substitute parts (SN74CBT3125 series and SN74CBTLV3125D) carry ROHS3 compliance certification. FST3125DR2G (onsemi) also carries ROHS3 compliance. All parts are REACH Unaffected and classified as EAR99 for export control purposes.

Q: Which substitute offers the best long-term availability? SN74CBT3125CD and SN74CBT3125CDR maintain Active production status, providing the most reliable long-term supply chain availability compared to Last Time Buy or Obsolete alternatives.

Request Quote (Ships tomorrow)

Part Number

Quantity

Company

Contact Name

E-mail

Message