FST3125MTC Equivalent & Substitute Parts

Part Overview

The FST3125MTC is a bus switch logic IC manufactured by onsemi in a 14-TSSOP package configuration. This component functions as a 1 x 1:1 bus switch with 4 independent circuits, designed for single supply operation across 4V to 5.5V. The FST3125MTC is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and production continuity. Substitute parts must maintain functional equivalence in bus switching topology, circuit configuration, and electrical operating parameters while accommodating available packaging and product status options.

Substiute Parts

FST3125MTC

onsemiIn Stock: 2371FST3125MTC Datasheet

Current PartRFQ

FST3125DTR2G

onsemiIn Stock: 895FST3125DTR2G Datasheet

UpgradeRFQ

FST3125MTCX

onsemiIn Stock: 37870FST3125MTCX Datasheet

SimilarRFQ

SN74CBT3125PW

Texas InstrumentsIn Stock: 1255SN74CBT3125PW Datasheet

DirectRFQ

SN74CBT3125PWR

Texas InstrumentsIn Stock: 5379SN74CBT3125PWR Datasheet

DirectRFQ

SN74CBT3125CDBR

Texas InstrumentsIn Stock: 29146SN74CBT3125CDBR Datasheet

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SN74CBT3125CPW

Texas InstrumentsIn Stock: 924SN74CBT3125CPW Datasheet

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SN74CBT3125CPWR

Texas InstrumentsIn Stock: 2487SN74CBT3125CPWR Datasheet

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SN74CBT3125DBR

Texas InstrumentsIn Stock: 2220SN74CBT3125DBR Datasheet

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SN74CBT3125DBRE4

Texas InstrumentsIn Stock: 844SN74CBT3125DBRE4 Datasheet

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SN74CBT3125DGVR

Texas InstrumentsIn Stock: 3319SN74CBT3125DGVR Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for the FST3125MTC is determined by the following criteria:

Primary Substitution Parameters:

• Bus switch type with 1 x 1:1 circuit topology
• 4 independent circuits
• Single supply voltage operation
• Voltage supply range compatibility (minimum 4V, maximum 5.5V)
• Operating temperature range (minimum -40°C, maximum 85°C)
• Surface mount technology
• Moisture sensitivity level 1 (unlimited)

Package Considerations:

• 14-TSSOP package is the primary form factor
• 14-SSOP package variants are acceptable with mechanical compatibility verification
• 14-TVSOP package variants are acceptable with mechanical compatibility verification

Compliance & Status:

• RoHS3 compliance preferred for new designs
• Product status (active, last time buy, or obsolete) affects long-term availability

Substitute parts are grouped into three categories: upgrade options with extended temperature range, direct equivalents with identical specifications, and similar variants with package or packaging format differences.

Parameter Comparison

Engineering Selection Recommendations

Upgrade Path (Extended Temperature Range): FST3125DTR2G offers extended operating temperature range (-55°C to 125°C) compared to the FST3125MTC (-40°C to 85°C) while maintaining identical 14-TSSOP packaging and 4V to 5.5V supply voltage. This part is RoHS3 compliant and suitable for applications requiring wider temperature operation.

Direct Equivalents (Identical Specifications): FST3125MTCX maintains the exact electrical and thermal specifications of FST3125MTC with identical 14-TSSOP packaging, -40°C to 85°C operating range, and 4V to 5.5V supply voltage. This part is RoHS3 compliant and available in higher inventory quantities (37,800 pcs).

Texas Instruments Alternatives (14-TSSOP Package): SN74CBT3125PW, SN74CBT3125PWR, SN74CBT3125CPW, and SN74CBT3125CPWR are functionally equivalent bus switches from Texas Instruments. These parts operate across 4.5V to 5.5V (narrower minimum supply than FST3125MTC) with identical -40°C to 85°C temperature range and 14-TSSOP packaging. All are RoHS3 compliant. SN74CBT3125CPW and SN74CBT3125CPWR carry active product status, providing superior long-term availability.

Package Variants (14-SSOP): SN74CBT3125CDBR, SN74CBT3125DBR, and SN74CBT3125DBRE4 provide bus switch functionality in 14-SSOP package (0.209", 5.30mm width) instead of 14-TSSOP. These require PCB layout modification due to different pin spacing. SN74CBT3125CDBR is active status; others are last time buy or discontinued.

Package Variant (14-TVSOP): SN74CBT3125DGVR operates in 14-TVSOP package (0.173", 4.40mm width) with last time buy status. This variant requires verification of mechanical compatibility with existing PCB designs.

Frequently Asked Questions (FAQ)

Q: Can I directly replace FST3125MTC with SN74CBT3125CPW? A: Yes, for applications operating within 4.5V to 5.5V supply range. Both parts share identical 1 x 1:1 bus switch topology, 4 independent circuits, -40°C to 85°C operating temperature, and 14-TSSOP packaging. The SN74CBT3125CPW has active product status, ensuring continued availability. If your design requires 4V minimum supply voltage, FST3125MTCX is the appropriate substitute.

Q: What is the difference between 14-TSSOP and 14-SSOP packages? A: 14-TSSOP has 0.173" (4.40mm) width; 14-SSOP has 0.209" (5.30mm) width. These are mechanically incompatible without PCB redesign. Pin pitch and lead configuration differ, requiring layout modification for SSOP variants.

Q: Is FST3125DTR2G a suitable upgrade for FST3125MTC? A: Yes. FST3125DTR2G extends operating temperature to -55°C to 125°C while maintaining identical 14-TSSOP packaging, 4V to 5.5V supply voltage, and bus switch functionality. This upgrade is appropriate for applications requiring wider temperature operation. RoHS3 compliance is included.

Q: Why do Texas Instruments parts specify 4.5V minimum instead of 4V? A: This reflects the specific electrical characterization of the SN74CBT3125 series. FST3125 variants support 4V minimum. For designs operating below 4.5V, use FST3125MTCX or FST3125DTR2G.

Q: Which substitute has the best long-term availability? A: SN74CBT3125CPW and SN74CBT3125CPWR carry active product status from Texas Instruments, indicating ongoing production and support. FST3125MTCX from onsemi is also available with high inventory (37,800 pcs) despite obsolete classification.

Q: Can I use 14-TVSOP variant SN74CBT3125DGVR as a drop-in replacement? A: No. While 14-TVSOP shares the 0.173" (4.40mm) width with 14-TSSOP, the package geometry differs. Mechanical compatibility must be verified against your specific PCB footprint before use.