FQB3N40TM Equivalent & Substitute Parts

Part Overview

The FQB3N40TM is an N-Channel MOSFET manufactured by onsemi, rated for 400V drain-to-source voltage with 2.5A continuous drain current. The device is housed in a Surface Mount TO-263 (D2PAK) package and is part of the QFET® series. This part is classified as obsolete, making identification of equivalent and substitute components necessary for ongoing design support, maintenance, and production continuity. Substitute parts must maintain compatibility with the original electrical specifications and physical package requirements.

Key Parameters

Parameter	FQB3N40TM
Manufacturer	onsemi
FET Type	N-Channel
Technology	MOSFET (Metal Oxide)
Drain to Source Voltage (Vdss)	400 V
Current - Continuous Drain (Id) @ 25°C	2.5A (Tc)
Drive Voltage (Max Rds On)	10V
Rds On (Max) @ Id, Vgs	3.4Ohm @ 1.25A, 10V
Vgs(th) (Max) @ Id	5V @ 250µA
Gate Charge (Qg) (Max) @ Vgs	7.5 nC @ 10 V
Vgs (Max)	±30V
Input Capacitance (Ciss) (Max) @ Vds	230 pF @ 25 V
Power Dissipation (Max)	3.13W (Ta), 55W (Tc)
Operating Temperature	-55°C ~ 150°C (TJ)
Mounting Type	Surface Mount
Package / Case	TO-263-3, D2PAK (2 Leads + Tab), TO-263AB
Moisture Sensitivity Level (MSL)	1 (Unlimited)
Product Status	Obsolete

Substitute Part Grouping Explanation

Substitution of the FQB3N40TM is determined by the following critical electrical and mechanical parameters:

Primary Substitution Criteria:

FET Type: N-Channel MOSFET (Metal Oxide technology)
Drain to Source Voltage (Vdss): Must equal or exceed 400V
Continuous Drain Current (Id): Must equal or exceed 2.5A at 25°C
Drive Voltage: 10V gate drive compatibility
Package Type: Surface Mount TO-263 (D2PAK) form factor
Operating Temperature Range: Must support -55°C to 150°C minimum

Secondary Compatibility Parameters:

Rds On (Max): Lower or equal values indicate improved performance
Gate Charge (Qg): Lower values reduce switching losses
Input Capacitance (Ciss): Lower values reduce gate drive requirements
Vgs (Max): Must accommodate ±30V gate voltage
Moisture Sensitivity Level: MSL 1 (Unlimited) preferred

Substitute parts are grouped based on voltage rating alignment. Parts with Vdss ratings equal to or greater than 400V are considered direct substitutes when all other electrical parameters meet or exceed the original specification.

Parameter Comparison

Parameter	FQB3N40TM (onsemi)	IRF540NSTRLPBF (Infineon)	IRF820ASTRL (Vishay)
FET Type	N-Channel	N-Channel	N-Channel
Technology	MOSFET (Metal Oxide)	MOSFET (Metal Oxide)	MOSFET (Metal Oxide)
Drain to Source Voltage (Vdss)	400 V	100 V	500 V
Current - Continuous Drain (Id) @ 25°C	2.5A (Tc)	33A (Tc)	2.5A (Tc)
Drive Voltage (Max Rds On)	10V	10V	10V
Rds On (Max) @ Id, Vgs	3.4Ohm @ 1.25A, 10V	44mOhm @ 16A, 10V	3Ohm @ 1.5A, 10V
Vgs(th) (Max) @ Id	5V @ 250µA	4V @ 250µA	4.5V @ 250µA
Gate Charge (Qg) (Max) @ Vgs	7.5 nC @ 10 V	71 nC @ 10 V	17 nC @ 10 V
Vgs (Max)	±30V	±20V	±30V
Input Capacitance (Ciss) (Max) @ Vds	230 pF @ 25 V	1960 pF @ 25 V	340 pF @ 25 V
Power Dissipation (Max)	3.13W (Ta), 55W (Tc)	130W (Tc)	50W (Tc)
Operating Temperature	-55°C ~ 150°C (TJ)	-55°C ~ 175°C (TJ)	-55°C ~ 150°C (TJ)
Mounting Type	Surface Mount	Surface Mount	Surface Mount
Package / Case	TO-263-3, D2PAK	D2PAK	TO-263-3, D2PAK
Moisture Sensitivity Level (MSL)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)
Product Status	Obsolete	Active	Active

Engineering Selection Recommendations

IRF820ASTRL (Vishay Siliconix) - Recommended Substitute

The IRF820ASTRL is the primary substitute for the FQB3N40TM. This device maintains electrical compatibility across all critical parameters: N-Channel MOSFET technology, 500V Vdss rating (exceeds 400V requirement), 2.5A continuous drain current (matches specification), and identical TO-263 (D2PAK) Surface Mount package. The IRF820ASTRL demonstrates superior performance with lower Rds On (3Ohm vs. 3.4Ohm) and higher power dissipation capability (50W vs. 55W at Tc). Operating temperature range (-55°C to 150°C) aligns with the original specification. The device is classified as Active, ensuring ongoing availability and supply chain continuity. Moisture Sensitivity Level 1 (Unlimited) matches the original part. RoHS non-compliance status should be evaluated against application requirements.

IRF540NSTRLPBF (Infineon Technologies) - Limited Substitution

The IRF540NSTRLPBF is not recommended as a direct substitute due to insufficient Vdss rating (100V vs. 400V required). While this device offers superior current handling (33A vs. 2.5A) and lower Rds On (44mOhm), the voltage rating is inadequate for applications requiring 400V operation. This part is suitable only for applications with reduced voltage requirements. The device is Active status with ROHS3 compliance. Gate voltage maximum rating is ±20V, which is lower than the ±30V specification of the original part.

Product Status Consideration

The FQB3N40TM is classified as Obsolete. The IRF820ASTRL and IRF540NSTRLPBF are both Active products, providing long-term design support and supply availability. Selection should prioritize Active status parts to ensure production continuity and future component availability.

Frequently Asked Questions (FAQ)

Q: Can the IRF540NSTRLPBF replace the FQB3N40TM in all applications?

A: No. The IRF540NSTRLPBF has a maximum Vdss rating of 100V, which is insufficient for applications requiring 400V operation. This part is suitable only for circuits with reduced voltage requirements below 100V.

Q: What is the primary advantage of the IRF820ASTRL as a substitute?

A: The IRF820ASTRL maintains full electrical compatibility with the FQB3N40TM while offering improved performance characteristics. It provides a higher Vdss rating (500V vs. 400V), lower on-resistance (3Ohm vs. 3.4Ohm), and greater power dissipation capability (50W vs. 55W at Tc). Both devices use identical TO-263 (D2PAK) Surface Mount packaging.

Q: Are there package compatibility concerns when substituting the FQB3N40TM?

A: No. Both substitute parts use the same TO-263-3, D2PAK (2 Leads + Tab), TO-263AB package format as the original FQB3N40TM. Direct board-level substitution is possible without PCB redesign.

Q: What is the significance of the Vgs (Max) rating difference between the FQB3N40TM and IRF540NSTRLPBF?

A: The FQB3N40TM supports ±30V gate voltage, while the IRF540NSTRLPBF supports ±20V. Applications using gate drive circuits that exceed ±20V will require the IRF820ASTRL or FQB3N40TM to prevent gate oxide damage.

Q: How does the Gate Charge (Qg) difference affect circuit performance?

A: The FQB3N40TM has a gate charge of 7.5 nC, while the IRF820ASTRL has 17 nC and the IRF540NSTRLPBF has 71 nC. Higher gate charge requires greater gate drive current and increases switching losses. The IRF820ASTRL's higher gate charge may require gate driver circuit evaluation in high-frequency switching applications.

Q: Is the IRF820ASTRL RoHS non-compliance status a concern?

A: RoHS compliance status depends on application requirements and regional regulations. The IRF820ASTRL is RoHS non-compliant, while the IRF540NSTRLPBF is ROHS3 compliant. Applications subject to RoHS requirements should select the IRF540NSTRLPBF if voltage rating permits, or evaluate alternative compliant parts.

Q: What is the operating temperature range compatibility?

A: The FQB3N40TM and IRF820ASTRL both support -55°C to 150°C operation. The IRF540NSTRLPBF extends to -55°C to 175°C, providing wider temperature margin. All three parts meet the minimum temperature specification of the original device.

Q: Can the IRF820ASTRL be used in high-frequency switching applications?

A: The IRF820ASTRL is suitable for high-frequency applications. However, the increased gate charge (17 nC vs. 7.5 nC) compared to the FQB3N40TM will result in higher gate drive power dissipation. Gate driver circuit capability should be verified to ensure adequate drive current at the target switching frequency.

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