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FST3257QSC Equivalent & Substitute Parts
Part Overview
The FST3257QSC 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 equivalent substitute parts necessary for new designs and ongoing production support. The FST3257QSC operates across a single supply voltage range of 3V to 5.5V with an operating temperature range of -40°C to 85°C, serving applications requiring signal routing and multiplexing functionality in compact form factors.
Substiute Parts
Key Parameters
| Parameter | FST3257QSC |
|---|---|
| Manufacturer | onsemi |
| Type | Multiplexer/Demultiplexer |
| Circuit Configuration | 4 x 2:1 |
| Independent Circuits | 1 |
| Voltage Supply Source | Single Supply |
| Voltage - Supply Range | 3V ~ 5.5V |
| Operating Temperature | -40°C ~ 85°C |
| Mounting Type | Surface Mount |
| Package / Case | 16-QSOP (0.154", 3.90mm Width) |
| Product Status | Obsolete |
| Moisture Sensitivity Level (MSL) | 1 (Unlimited) |
Substitute Part Grouping Explanation
Substitution for the FST3257QSC is determined by strict equivalence across the following critical parameters:
- Circuit Configuration: All substitutes must maintain 4 x 2:1 multiplexer/demultiplexer topology with 1 independent circuit
- Mounting Type: Surface mount only
- Operating Temperature Range: -40°C to 85°C minimum
- Voltage Supply Source: Single supply operation
- Package Compatibility: Substitutes are grouped by package type (16-QSOP, 16-SSOP, or 16-TSSOP)
Substitute parts are organized into three package families:
- 16-QSOP Package Group (0.154" width): PI5C3257QE, PI5C3257QEX, QS3257QG, QS3257QG8
- 16-SSOP Package Group (0.154" width): CBT3257ADS,118, SN74CBT3257CDBQR
- 16-TSSOP Package Group (0.173" width): 74FST3257DTR2G, CBT3257APW,118, PI5C3257LE, PI5C3257LEX
Parameter Comparison
| Part Number | Manufacturer | Circuit | Voltage Supply | Temp Range | Package | Product Status | RoHS Status | MSL |
|---|---|---|---|---|---|---|---|---|
| FST3257QSC | onsemi | 4 x 2:1 | 3V ~ 5.5V | -40°C ~ 85°C | 16-QSOP | Obsolete | Not Listed | 1 |
| 74FST3257DTR2G | onsemi | 4 x 2:1 | 4V ~ 5.5V | -40°C ~ 85°C | 16-TSSOP | Last Time Buy | ROHS3 Compliant | 1 |
| CBT3257ADS,118 | Nexperia USA Inc. | 4 x 2:1 | 4.5V ~ 5.5V | -40°C ~ 85°C | 16-SSOP | Active | ROHS3 Compliant | 1 |
| CBT3257APW,118 | Nexperia USA Inc. | 4 x 2:1 | 4.5V ~ 5.5V | -40°C ~ 85°C | 16-TSSOP | Active | ROHS3 Compliant | 1 |
| PI5C3257LE | Diodes Incorporated | 4 x 2:1 | 4.75V ~ 5.25V | -40°C ~ 85°C | 16-TSSOP | Last Time Buy | ROHS3 Compliant | 1 |
| PI5C3257LEX | Diodes Incorporated | 4 x 2:1 | 4.75V ~ 5.25V | -40°C ~ 85°C | 16-TSSOP | Last Time Buy | ROHS3 Compliant | 1 |
| PI5C3257QE | Diodes Incorporated | 4 x 2:1 | 4.75V ~ 5.25V | -40°C ~ 85°C | 16-QSOP | Active | ROHS3 Compliant | 1 |
| PI5C3257QEX | Diodes Incorporated | 4 x 2:1 | 4.75V ~ 5.25V | -40°C ~ 85°C | 16-QSOP | Active | ROHS3 Compliant | 1 |
| QS3257QG | Renesas Electronics Corporation | 4 x 2:1 | 4.75V ~ 5.25V | -40°C ~ 85°C | 16-QSOP | Active | ROHS3 Compliant | 1 |
| QS3257QG8 | Renesas Electronics Corporation | 4 x 2:1 | 4.75V ~ 5.25V | -40°C ~ 85°C | 16-QSOP | Active | ROHS3 Compliant | 1 |
| SN74CBT3257CDBQR | Texas Instruments | 4 x 2:1 | 4.5V ~ 5.5V | -40°C ~ 85°C | 16-SSOP | Active | ROHS3 Compliant | 2 |
Engineering Selection Recommendations
For 16-QSOP Package Compatibility (Direct Footprint Match)
PI5C3257QE and PI5C3257QEX from Diodes Incorporated are active production parts with ROHS3 compliance and identical 16-QSOP packaging. Both maintain the same 0.154" width as the FST3257QSC. PI5C3257QEX offers higher inventory availability (55,402 units) with Cut Tape and Digi-Reel packaging options. The voltage supply range narrows to 4.75V ~ 5.25V, which is compatible with standard 5V supply designs but excludes 3V operation.
QS3257QG and QS3257QG8 from Renesas Electronics Corporation provide alternative 16-QSOP sourcing with active product status and ROHS3 compliance. Both maintain identical electrical specifications to the Diodes parts with the same voltage and temperature ranges.
For 16-TSSOP Package (0.173" Width)
CBT3257APW,118 from Nexperia USA Inc. is an active production part with ROHS3 compliance in 16-TSSOP packaging. This part requires PCB layout modification due to the increased 0.173" width compared to the original 0.154" QSOP package. Voltage supply range is 4.5V ~ 5.5V.
74FST3257DTR2G from onsemi provides Last Time Buy status in 16-TSSOP packaging with ROHS3 compliance and 4V ~ 5.5V supply range. Inventory availability is substantial at 3,196 units.
PI5C3257LE and PI5C3257LEX from Diodes Incorporated offer 16-TSSOP alternatives with Last Time Buy status and ROHS3 compliance. PI5C3257LEX provides higher inventory (15,417 units) with Tape & Reel packaging.
For 16-SSOP Package (0.154" Width)
CBT3257ADS,118 from Nexperia USA Inc. is an active production part with ROHS3 compliance and identical 0.154" width to the original FST3257QSC. Voltage supply range is 4.5V ~ 5.5V with 1,900 units in stock.
SN74CBT3257CDBQR from Texas Instruments is an active production part with ROHS3 compliance in 16-SSOP packaging. This part carries MSL Level 2 (1 Year) moisture sensitivity versus Level 1 for other substitutes. Voltage supply range is 4.5V ~ 5.5V.
Frequently Asked Questions (FAQ)
Q: Can I use a 16-TSSOP substitute in place of the original 16-QSOP FST3257QSC without PCB modification?
A: No. The 16-TSSOP package has a 0.173" width compared to the 16-QSOP's 0.154" width. PCB layout and footprint modifications are required. Use 16-QSOP or 16-SSOP substitutes for direct footprint compatibility.
Q: What is the voltage supply difference between FST3257QSC and substitute parts?
A: The FST3257QSC operates from 3V ~ 5.5V. Most substitutes narrow this range to 4.5V ~ 5.5V (Nexperia and Texas Instruments) or 4.75V ~ 5.25V (Diodes and Renesas). Designs requiring 3V operation cannot use these substitutes without verification of alternative parts.
Q: Which substitute offers the best long-term availability?
A: PI5C3257QEX from Diodes Incorporated has the highest inventory (55,402 units) and active product status. QS3257QG and QS3257QG8 from Renesas also maintain active status with substantial inventory levels (5,805 and 16,759 units respectively).
Q: Are all substitutes ROHS3 compliant?
A: All listed substitutes carry ROHS3 compliance. The original FST3257QSC does not list RoHS status. All substitutes are REACH Unaffected.
Q: What is the difference between PI5C3257QE and PI5C3257QEX?
A: Both parts are electrically identical with the same 16-QSOP package and specifications. PI5C3257QEX offers higher inventory (55,402 units) and is supplied in Cut Tape and Digi-Reel packaging, while PI5C3257QE is supplied in Tube packaging with lower inventory (10,100 units).
Q: Can I substitute a part with MSL Level 2 (SN74CBT3257CDBQR) for the original MSL Level 1 part?
A: MSL Level 2 requires 1-year shelf life management versus unlimited for Level 1. This affects storage and handling procedures. Substitution is technically feasible but requires updated moisture control protocols in manufacturing and storage environments.
Q: Which substitute maintains the widest voltage supply range?
A: 74FST3257DTR2G from onsemi maintains 4V ~ 5.5V, which is the widest range among substitutes. However, this still excludes 3V operation available on the original FST3257QSC.
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