FDS4685 Equivalent & Substitute Parts

Part Overview

The FDS4685 is an active P-Channel MOSFET manufactured by onsemi, rated for 40V drain-to-source voltage with 8.2A continuous drain current at 25°C. The device is housed in an 8-SOIC surface mount package and is part of the PowerTrench® series. This component is ROHS3 compliant and carries unlimited moisture sensitivity level (MSL 1), making it suitable for standard industrial and commercial applications.

Substitute parts are identified when equivalent electrical performance and mechanical compatibility can be maintained within the specified parameter ranges. The FDS4685 has four qualified substitute options that meet the core functional requirements while offering variations in current handling, on-resistance, and package configurations.

Substiute Parts

FDS4685

onsemiIn Stock: 18602FDS4685 Datasheet

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AO4485

UMWIn Stock: 90167AO4485 Datasheet

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DMP4025LSS-13

Diodes IncorporatedIn Stock: 3347DMP4025LSS-13 Datasheet

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IRF7416TRPBF

Infineon TechnologiesIn Stock: 36304IRF7416TRPBF Datasheet

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RS1G201ATTB1

Rohm SemiconductorIn Stock: 8286RS1G201ATTB1 Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for the FDS4685 is determined by the following core parameters:

Primary Compatibility Criteria:

• FET Type: P-Channel (required match)
• Drain to Source Voltage (Vdss): 40V minimum (equal or higher acceptable)
• Mounting Type: Surface Mount (required match)
• Operating Temperature Range: -55°C to 150°C (required match)
• RoHS Status: ROHS3 Compliant (required match)
• Moisture Sensitivity Level: MSL 1 (required match)

Secondary Performance Parameters:

• Current - Continuous Drain (Id) @ 25°C: 8.2A minimum (equal or higher acceptable)
• Rds On (Max) @ Id, Vgs: 27mOhm maximum (lower values acceptable)
• Vgs(th) (Max) @ Id: 3V maximum (lower values acceptable)
• Gate Charge (Qg) (Max) @ Vgs: 27nC maximum (lower values acceptable)
• Input Capacitance (Ciss) (Max) @ Vds: 1872pF maximum (lower values acceptable)
• Power Dissipation (Max): 2.5W minimum (equal or higher acceptable)

The four identified substitutes meet all primary compatibility criteria. Variations in package configuration (8-SOP, 8-SO, 8-HSOP) are acceptable provided the electrical footprint remains compatible with the application circuit design.

Parameter Comparison

Engineering Selection Recommendations

All four substitute parts maintain active product status and ROHS3 compliance, meeting the regulatory and environmental requirements of the FDS4685.

AO4485 (UMW): This substitute provides 10A continuous drain current, exceeding the FDS4685 specification by 1.8A. The on-resistance is reduced to 15mOhm, offering improved thermal performance. Gate charge increases to 55nC, which may affect switching speed in high-frequency applications. Input capacitance rises to 3000pF. Power dissipation is reduced to 1.7W. This part is suitable for applications requiring higher current capacity with acceptable switching speed trade-offs.

DMP4025LSS-13 (Diodes Incorporated): This substitute provides 6A continuous drain current, which is below the FDS4685 specification by 2.2A. On-resistance is 25mOhm, slightly lower than the main part. Gate charge is 33.7nC and input capacitance is 1640pF, both favorable for switching performance. Power dissipation is 1.52W. This part is suitable only for applications with current requirements not exceeding 6A.

IRF7416TRPBF (Infineon): This substitute provides 10A continuous drain current and 20mOhm on-resistance. However, the drain-to-source voltage rating is 30V, which is 10V below the FDS4685 specification. This voltage limitation restricts use to applications with maximum operating voltages of 30V. Gate charge is 92nC and input capacitance is 1700pF. Power dissipation matches the main part at 2.5W. This part is suitable only for applications with voltage requirements not exceeding 30V.

RS1G201ATTB1 (Rohm Semiconductor): This substitute provides 20A continuous drain current at Ta and 78A at Tc, significantly exceeding the FDS4685 specification. On-resistance is 5.2mOhm, substantially lower than the main part. Gate charge is 130nC and input capacitance is 6890pF, both significantly higher, which may impact switching speed. Power dissipation is 3W at Ta and 40W at Tc. The package is 8-HSOP rather than 8-SOIC, requiring PCB layout verification. This part is suitable for high-current applications where thermal management and switching speed are not critical constraints.

Frequently Asked Questions (FAQ)

Q: Can the AO4485 directly replace the FDS4685 in all applications?

A: The AO4485 meets all primary compatibility criteria and exceeds current specifications. However, the increased gate charge (55nC vs. 27nC) and input capacitance (3000pF vs. 1872pF) may affect switching frequency performance. Verify that the gate driver circuit can accommodate the higher capacitive load and that switching speed requirements are not compromised.

Q: Why is the IRF7416TRPBF listed as a substitute if its Vdss is only 30V?

A: The IRF7416TRPBF is listed as a qualified substitute for applications where the maximum operating voltage does not exceed 30V. It is not suitable for circuits requiring the full 40V rating of the FDS4685. Confirm application voltage requirements before selection.

Q: What are the package differences between the substitute parts?

A: The FDS4685 uses 8-SOIC packaging. The AO4485 uses 8-SOP, the DMP4025LSS-13 and IRF7416TRPBF use 8-SO, and the RS1G201ATTB1 uses 8-HSOP. While all are 8-pin surface mount packages with 0.154" (3.90mm) width, the pin pitch and thermal characteristics may differ. Verify PCB footprint compatibility before layout implementation.

Q: Is the DMP4025LSS-13 suitable for applications requiring 8.2A continuous current?

A: No. The DMP4025LSS-13 is rated for 6A continuous drain current, which is 2.2A below the FDS4685 specification. This part is suitable only for applications with current requirements not exceeding 6A. Exceeding this rating will result in thermal stress and potential device failure.

Q: How does the RS1G201ATTB1 compare thermally to the FDS4685?

A: The RS1G201ATTB1 provides significantly higher power dissipation capability (3W at Ta, 40W at Tc) compared to the FDS4685 (2.5W at Ta). The substantially lower on-resistance (5.2mOhm vs. 27mOhm) reduces conduction losses. However, the higher gate charge (130nC) and input capacitance (6890pF) increase switching losses. Thermal performance depends on the specific application duty cycle and heat dissipation design.

Q: Are all substitute parts ROHS3 compliant?

A: Yes. All four substitute parts are ROHS3 compliant with MSL 1 (Unlimited) moisture sensitivity level, matching the FDS4685 environmental and regulatory specifications.

Q: What is the primary limitation of the DMP4025LSS-13?

A: The primary limitation is the reduced continuous drain current rating of 6A, which is 27% below the FDS4685 specification. This part is suitable only for lower-current applications and cannot be used as a direct replacement in circuits designed for 8.2A operation.

Q: Can gate charge differences affect circuit performance?

A: Yes. Gate charge directly impacts switching speed and gate driver power requirements. The FDS4685 has 27nC gate charge. Substitutes with higher gate charge (AO4485 at 55nC, DMP4025LSS-13 at 33.7nC, IRF7416TRPBF at 92nC, RS1G201ATTB1 at 130nC) require longer switching times and higher gate driver current. Verify that the gate driver circuit can supply the required charge within the application's switching frequency constraints.

Q: What is the significance of on-resistance (Rds On) in substitute selection?

A: On-resistance determines conduction losses and thermal dissipation. Lower on-resistance reduces power loss and heat generation. The FDS4685 has 27mOhm on-resistance. Substitutes with lower on-resistance (AO4485 at 15mOhm, DMP4025LSS-13 at 25mOhm, IRF7416TRPBF at 20mOhm, RS1G201ATTB1 at 5.2mOhm) provide improved efficiency. Substitutes with higher on-resistance increase thermal load and may require enhanced cooling.