IRF644S N-Channel MOSFET 250V 14A Equivalent & Substitute Parts

Part Overview

The IRF644S is an N-Channel MOSFET manufactured by Vishay Siliconix, rated for 250V drain-to-source voltage and 14A continuous drain current in a Surface Mount TO-263 (D2PAK) package. This device is classified as obsolete, making identification of equivalent and substitute parts necessary for ongoing design support and production continuity. The IRF644S serves in switching applications requiring moderate voltage and current ratings with the compact D2PAK form factor.

Substiute Parts

IRF644S

Vishay SiliconixIn Stock: 6411IRF644S Datasheet

Current PartRFQ

IRF644SPBF

Vishay SiliconixIn Stock: 2977IRF644SPBF Datasheet

DirectRFQ

STB18NF25

STMicroelectronicsIn Stock: 1376STB18NF25 Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the IRF644S is determined by strict equivalence across the following critical parameters:

Primary Substitution Criteria:

• Drain-to-Source Voltage (Vdss): 250V minimum
• N-Channel MOSFET technology
• Surface Mount TO-263 (D2PAK) package
• Gate threshold voltage compatibility (Vgs(th) @ 250µA)
• Maximum gate voltage rating (±20V)

Secondary Compatibility Parameters:

• Continuous drain current rating (minimum 14A at Tc)
• On-resistance (Rds On) characteristics
• Gate charge and input capacitance
• Operating temperature range overlap

The IRF644SPBF is a direct equivalent from the same manufacturer (Vishay Siliconix) with identical electrical specifications and packaging. The STB18NF25 from STMicroelectronics is a manufacturer-recommended substitute that exceeds the IRF644S specifications in drain current (17A vs. 14A) and on-resistance performance (165mOhm vs. 280mOhm), while maintaining voltage and package compatibility.

Parameter Comparison

Engineering Selection Recommendations

IRF644SPBF (Direct Equivalent)

The IRF644SPBF is the primary substitute for the obsolete IRF644S. This part maintains identical electrical specifications and packaging while offering active product status. The IRF644SPBF is ROHS3 compliant and REACH affected, making it suitable for applications requiring modern regulatory compliance. Inventory availability (2900 pcs) supports production requirements. This substitute is appropriate for direct replacement in existing designs without circuit modification.

STB18NF25 (Performance-Enhanced Substitute)

The STB18NF25 from STMicroelectronics is a manufacturer-recommended alternative that provides enhanced performance characteristics. This device delivers higher continuous drain current (17A vs. 14A) and significantly lower on-resistance (165mOhm vs. 280mOhm), resulting in reduced power dissipation and improved thermal efficiency. The STB18NF25 features an extended operating temperature range (-55°C to 175°C) and carries AEC-Q101 automotive qualification. Gate charge is reduced to 29.5nC, enabling faster switching operation. This substitute is suitable for applications where improved performance margins and automotive-grade reliability are beneficial. The STB18NF25 is ROHS3 compliant and REACH unaffected.

Compliance Considerations

Both substitute parts are ROHS3 compliant, addressing regulatory requirements that the obsolete IRF644S does not meet. Selection between IRF644SPBF and STB18NF25 depends on design requirements: choose IRF644SPBF for specification-matched replacement, or STB18NF25 for enhanced performance and automotive-grade qualification.

Frequently Asked Questions (FAQ)

Q: Can the IRF644SPBF be used as a direct replacement for the IRF644S?

A: Yes. The IRF644SPBF is electrically and mechanically identical to the IRF644S, with matching Vdss (250V), Id (14A), Rds On (280mOhm), and TO-263 (D2PAK) packaging. The primary difference is product status (active vs. obsolete) and regulatory compliance (ROHS3 compliant). No circuit modifications are required.

Q: What are the advantages of using the STB18NF25 over the IRF644SPBF?

A: The STB18NF25 provides higher continuous drain current (17A vs. 14A), lower on-resistance (165mOhm vs. 280mOhm), reduced gate charge (29.5nC vs. 68nC), and extended operating temperature range (-55°C to 175°C vs. -55°C to 150°C). These characteristics reduce power dissipation and enable faster switching. The STB18NF25 also carries AEC-Q101 automotive qualification.

Q: Are all three parts pin-compatible?

A: Yes. The IRF644S, IRF644SPBF, and STB18NF25 all use the TO-263 (D2PAK) package with identical pinout: Gate, Drain, and Source connections. Direct PCB substitution is possible without layout modification.

Q: What is the difference in gate charge between these parts?

A: The IRF644S and IRF644SPBF both have 68nC gate charge at 10V. The STB18NF25 has significantly lower gate charge at 29.5nC, enabling faster gate switching and reduced driver power requirements.

Q: Which substitute should be selected for new designs?

A: For new designs, the IRF644SPBF is appropriate if specification matching to the original IRF644S is required. The STB18NF25 is recommended if improved performance, lower on-resistance, and automotive-grade qualification provide design benefits. Both parts are active and ROHS3 compliant.

Q: Are there packaging differences between these parts?

A: The IRF644S is supplied in standard packaging. The IRF644SPBF is supplied in Tube packaging. The STB18NF25 is supplied in Cut Tape (CT) and Digi-Reel® packaging. All three use the same TO-263 (D2PAK) component package for PCB mounting.

Q: What is the moisture sensitivity level for these parts?

A: All three parts have Moisture Sensitivity Level (MSL) 1, indicating unlimited shelf life without moisture control requirements.

Q: How do the input capacitance values compare?

A: The IRF644S and IRF644SPBF both have 1300pF input capacitance at 25V. The STB18NF25 has lower input capacitance at 1000pF, contributing to faster switching characteristics and reduced gate drive requirements.