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FST3345MTCX Equivalent & Substitute Parts
Part Overview
The FST3345MTCX is an 8 x 1:1 bus switch logic IC manufactured by onsemi in a 20-TSSOP package. This component is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement. The FST3345MTCX operates with a single supply voltage between 4V and 5.5V, supporting applications requiring bus switching functionality across eight independent channels with 1:1 switching ratios.
Substiute Parts
Key Parameters
| Parameter | Value |
|---|---|
| Manufacturer Part Number | FST3345MTCX |
| Manufacturer | onsemi |
| Category | Logic |
| Type | Bus Switch |
| Circuit Configuration | 8 x 1:1 |
| Independent Circuits | 1 |
| Voltage Supply Source | Single Supply |
| Voltage - Supply Range | 4V ~ 5.5V |
| Operating Temperature Range | -40°C ~ 85°C |
| Mounting Type | Surface Mount |
| Package / Case | 20-TSSOP (0.173", 4.40mm Width) |
| Product Status | Obsolete |
| Moisture Sensitivity Level (MSL) | 1 (Unlimited) |
| REACH Status | REACH Unaffected |
Substitute Part Grouping Explanation
Substitution for the FST3345MTCX is determined by strict alignment of the following electrical and mechanical parameters:
Circuit Configuration: All substitute parts must maintain the 8 x 1:1 bus switch topology with a single independent circuit.
Voltage Supply Range: Substitute parts must operate within or encompass the 4V to 5.5V supply voltage range of the original part.
Operating Temperature: Substitute parts must support the -40°C to 85°C operating temperature range.
Package Compatibility: Primary substitutes maintain the 20-TSSOP package (0.173", 4.40mm width). Secondary substitutes in alternative packages (20-SSOP, 20-TVSOP) are listed for reference but require PCB layout verification.
Mounting Type: All substitutes are surface mount components.
Substitute parts are grouped into three categories based on their relationship to the FST3345MTCX:
Parametric Equivalents: Parts with identical electrical specifications and the same package type.
Direct Manufacturer Alternatives: Parts from different manufacturers meeting all electrical and package requirements.
Similar Parts: Parts with compatible electrical specifications but different package types or minor parameter variations.
Parameter Comparison
| Part Number | Manufacturer | Circuit | Voltage Supply (V) | Temp Range (°C) | Package | Product Status | RoHS Status | MSL |
|---|---|---|---|---|---|---|---|---|
| FST3345MTCX | onsemi | 8 x 1:1 | 4.0 ~ 5.5 | -40 ~ 85 | 20-TSSOP | Obsolete | Not Specified | 1 |
| FST3245MTCX | onsemi | 8 x 1:1 | 4.0 ~ 5.5 | -40 ~ 85 | 20-TSSOP | Obsolete | ROHS3 Compliant | 1 |
| SN74CBT3245APWR | Texas Instruments | 8 x 1:1 | 4.0 ~ 5.5 | -40 ~ 85 | 20-TSSOP | Last Time Buy | ROHS3 Compliant | 1 |
| SN74CBT3345CDBQR | Texas Instruments | 8 x 1:1 | 4.5 ~ 5.5 | -40 ~ 85 | 20-SSOP | Active | ROHS3 Compliant | 2 |
| SN74CBT3345CPW | Texas Instruments | 8 x 1:1 | 4.5 ~ 5.5 | -40 ~ 85 | 20-TSSOP | Active | ROHS3 Compliant | 1 |
| SN74CBT3345CPWR | Texas Instruments | 8 x 1:1 | 4.5 ~ 5.5 | -40 ~ 85 | 20-TSSOP | Active | ROHS3 Compliant | 1 |
| SN74CBT3345DGVR | Texas Instruments | 8 x 1:1 | 4.5 ~ 5.5 | -40 ~ 85 | 20-TVSOP | Last Time Buy | ROHS3 Compliant | 1 |
| SN74CBT3345PW | Texas Instruments | 8 x 1:1 | 4.5 ~ 5.5 | -40 ~ 85 | 20-TSSOP | Last Time Buy | ROHS3 Compliant | 1 |
| SN74CBT3345PWR | Texas Instruments | 8 x 1:1 | 4.5 ~ 5.5 | -40 ~ 85 | 20-TSSOP | Last Time Buy | ROHS3 Compliant | 1 |
| SN74CBT3245CPWR | Texas Instruments | 8 x 1:1 | 4.0 ~ 5.5 | -40 ~ 85 | 20-TSSOP | Active | ROHS3 Compliant | 1 |
Engineering Selection Recommendations
For new designs and ongoing production, SN74CBT3345CPWR (Texas Instruments) is the primary recommended substitute. This part maintains identical electrical specifications to the FST3345MTCX, operates within the required voltage and temperature ranges, and carries Active product status with ROHS3 compliance. The 20-TSSOP package ensures direct PCB compatibility without layout modifications.
SN74CBT3245CPWR (Texas Instruments) serves as an alternative parametric equivalent with Active product status. This part extends the lower voltage supply limit to 4.0V, matching the FST3345MTCX specification, and provides ROHS3 compliance with unlimited moisture sensitivity rating.
For applications with relaxed voltage requirements (4.5V minimum), SN74CBT3345CPW and SN74CBT3345PWR provide additional options with established supply availability, though both carry Last Time Buy status indicating limited future procurement windows.
SN74CBT3345CDBQR is available in Active status but uses a 20-SSOP package (0.154", 3.90mm width) instead of the standard 20-TSSOP. This package variant requires PCB footprint verification and is suitable only when layout modifications are feasible.
FST3245MTCX (onsemi) maintains the same manufacturer lineage and package compatibility but carries Obsolete status, limiting its viability for long-term supply assurance.
Frequently Asked Questions (FAQ)
Q: Can SN74CBT3345CPWR directly replace FST3345MTCX without PCB modifications?
A: Yes. Both parts use the 20-TSSOP package with identical pinout and footprint dimensions (0.173", 4.40mm width). No PCB layout changes are required for this substitution.
Q: What is the voltage supply difference between FST3345MTCX and SN74CBT3345CPWR?
A: The FST3345MTCX operates at 4.0V to 5.5V, while SN74CBT3345CPWR operates at 4.5V to 5.5V. The SN74CBT3345CPWR has a higher minimum voltage threshold by 0.5V. Verify your circuit's minimum supply voltage before selection.
Q: Why is SN74CBT3245CPWR listed as a parametric equivalent?
A: SN74CBT3245CPWR maintains the identical 8 x 1:1 circuit configuration, 20-TSSOP package, and operating temperature range. It extends the lower voltage limit to 4.0V, matching the FST3345MTCX specification exactly. Both parts are electrically interchangeable within their specified voltage ranges.
Q: Can I use SN74CBT3345CDBQR as a substitute?
A: SN74CBT3345CDBQR is electrically compatible but uses a 20-SSOP package (0.154", 3.90mm width) instead of 20-TSSOP. This package difference requires PCB footprint verification and potential layout redesign. Use only if your design accommodates the smaller package width.
Q: What does "Last Time Buy" status mean for SN74CBT3345PW and SN74CBT3345PWR?
A: Last Time Buy status indicates the manufacturer has announced end-of-life for these parts. Existing inventory is available, but future procurement is not guaranteed. These parts are suitable for current production runs but not recommended for new long-term designs.
Q: Are all substitute parts ROHS3 compliant?
A: All Texas Instruments substitutes (SN74CBT series) carry ROHS3 compliance. FST3245MTCX also carries ROHS3 compliance. The original FST3345MTCX does not specify RoHS status. Verify compliance requirements for your application before final selection.
Q: What is the Moisture Sensitivity Level (MSL) difference?
A: Most substitutes maintain MSL 1 (Unlimited), matching the FST3345MTCX. SN74CBT3345CDBQR carries MSL 2 (1 Year), requiring stricter moisture control during storage and handling. Verify your manufacturing environment's moisture control capabilities if selecting this part.
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