FDB8444 N-Channel MOSFET 40V 70A Equivalent & Substitute Parts

Part Overview

The FDB8444 is an N-Channel MOSFET manufactured by onsemi, rated for 40V drain-to-source voltage and 70A continuous drain current in a Surface Mount TO-263 (D2PAK) package. This device is part of the PowerTrench® series and is currently classified as obsolete. Due to its obsolete status, equivalent and substitute parts from active manufacturers are necessary for new designs and ongoing production requirements. Substitute parts must maintain compatibility with the TO-263 (D2PAK) package footprint and meet or exceed the electrical performance specifications of the original device.

Substiute Parts

FDB8444

onsemiIn Stock: 15471FDB8444 Datasheet

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AOB4184

Alpha & Omega Semiconductor Inc.In Stock: 22678AOB4184 Datasheet

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IXTA100N04T2

IXYSIn Stock: 2810IXTA100N04T2 Datasheet

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STB100NF04T4

STMicroelectronicsIn Stock: 15280STB100NF04T4 Datasheet

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STB120N4F6

STMicroelectronicsIn Stock: 15166STB120N4F6 Datasheet

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STB170NF04

STMicroelectronicsIn Stock: 26308STB170NF04 Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitute parts for the FDB8444 are selected based on strict electrical and mechanical compatibility criteria. The primary substitution parameters are:

Critical Matching Parameters:

• Drain-to-Source Voltage (Vdss): Must equal 40V
• Package Type: Must be TO-263 (D2PAK) or equivalent Surface Mount configuration
• FET Type: Must be N-Channel MOSFET
• Operating Temperature Range: Must support -55°C to 175°C (TJ)
• Mounting Type: Must be Surface Mount

Performance Compatibility Parameters:

• Continuous Drain Current (Id): Substitute must meet or exceed 70A (Tc)
• On-Resistance (Rds On): Lower or equal values indicate improved performance
• Gate Charge (Qg): Lower values indicate faster switching characteristics
• Power Dissipation: Must support thermal requirements of the application

All substitute parts listed maintain the 40V Vdss rating and TO-263 (D2PAK) package configuration. Substitutes are grouped by their ability to meet or exceed the 70A continuous drain current specification while maintaining electrical and thermal compatibility.

Parameter Comparison

Engineering Selection Recommendations

Primary Substitutes (Recommended for Direct Replacement):

STB170NF04 (STMicroelectronics) - This part is the closest electrical match to the FDB8444. It provides 80A continuous drain current, exceeding the 70A requirement, with comparable on-resistance of 5 mOhm at 40A. The STB170NF04 is an active product with ROHS3 compliance and maintains the TO-263 (D2PAK) package footprint. Higher power dissipation (300W) provides thermal margin for demanding applications.

STB120N4F6 (STMicroelectronics) - This active product offers 80A continuous drain current with superior on-resistance of 4 mOhm at 40A, providing improved efficiency. It includes AEC-Q101 automotive qualification, making it suitable for automotive and industrial applications. ROHS3 compliant with TO-263 (D2PAK) package compatibility.

Secondary Substitutes (Higher Current Capability):

STB100NF04T4 (STMicroelectronics) - Rated for 120A continuous drain current with 4.6 mOhm on-resistance, this part provides significant performance headroom. It is an active product with AEC-Q101 automotive qualification and ROHS3 compliance. The higher current rating and power dissipation (300W) accommodate applications requiring enhanced thermal performance.

IXTA100N04T2 (IXYS) - This active product from the TrenchT2™ series delivers 100A continuous drain current with 7 mOhm on-resistance. It features lower gate charge (25.5 nC) for faster switching characteristics and is ROHS3 compliant with TO-263AA package compatibility.

Alternative Substitute (Lower Current Capability):

AOB4184 (Alpha & Omega Semiconductor) - This active product is rated for 50A continuous drain current, which is below the FDB8444 specification. It is suitable only for applications where the 70A requirement can be reduced or where multiple devices are paralleled. It offers the lowest gate charge (35 nC) among substitutes, enabling high-frequency switching applications. ROHS3 compliant with TO-263 (D2PAK) package.

All recommended substitutes maintain the 40V Vdss rating, TO-263 (D2PAK) package footprint, and -55°C to 175°C operating temperature range. Selection should be based on specific application requirements for current capacity, on-resistance, switching frequency, and thermal management.

Frequently Asked Questions (FAQ)

Q: Can the FDB8444 be directly replaced with any of the listed substitutes?

A: Direct replacement is possible with STB170NF04, STB120N4F6, STB100NF04T4, and IXTA100N04T2, as all maintain the 40V Vdss rating and TO-263 (D2PAK) package footprint. AOB4184 is suitable only if the application can operate at 50A continuous drain current or lower. PCB layout and thermal management should be verified for each substitute.

Q: What is the primary reason for finding substitutes for the FDB8444?

A: The FDB8444 is classified as obsolete. Substitute parts from active manufacturers ensure long-term availability, ongoing production support, and compliance with current RoHS and REACH regulations.

Q: Are all substitute parts ROHS3 compliant?

A: Yes, all listed substitute parts are ROHS3 compliant, matching the environmental compliance of the original FDB8444.

Q: Which substitute offers the best on-resistance performance?

A: STB120N4F6 provides the lowest on-resistance at 4 mOhm (measured at 40A, 10V), followed by STB100NF04T4 at 4.6 mOhm (measured at 50A, 10V). Lower on-resistance reduces power dissipation and heat generation.

Q: What is the difference between the TO-263 and TO-263AA packages?

A: Both are Surface Mount D2PAK configurations with identical pin layouts and footprints. TO-263AA and TO-263AB are variant designations from different manufacturers. All listed parts are mechanically compatible with standard TO-263 (D2PAK) PCB layouts.

Q: Which substitute has the fastest switching characteristics?

A: IXTA100N04T2 has the lowest gate charge at 25.5 nC (measured at 10V), enabling the fastest switching speed. AOB4184 also offers low gate charge at 35 nC. Lower gate charge reduces switching losses in high-frequency applications.

Q: Can I use AOB4184 as a direct replacement if my application only requires 50A?

A: Yes, AOB4184 is suitable for applications rated at 50A continuous drain current or lower. It is an active product with ROHS3 compliance and maintains the TO-263 (D2PAK) package footprint. Verify that the lower current rating meets your specific application requirements.

Q: Do any substitutes include automotive qualification?

A: Yes, STB100NF04T4 and STB120N4F6 both carry AEC-Q101 automotive qualification, making them suitable for automotive and safety-critical applications.

Q: What is the operating temperature range for all substitutes?

A: All substitute parts operate across the same temperature range as the FDB8444: -55°C to 175°C (TJ), ensuring thermal compatibility in extreme environment applications.

Q: How do I select between STB170NF04 and STB120N4F6?

A: Both are excellent substitutes. STB170NF04 provides slightly higher on-resistance (5 mOhm) but higher power dissipation (300W). STB120N4F6 offers superior on-resistance (4 mOhm) and includes AEC-Q101 automotive qualification. Choose STB120N4F6 for efficiency-critical or automotive applications; choose STB170NF04 for thermal margin in high-power applications.