FQL40N50 N-Channel 500V 40A MOSFET Equivalent & Substitute Parts

Part Overview

The FQL40N50 is an N-Channel 500V 40A MOSFET manufactured by onsemi in the QFET® series, housed in a TO-264-3 through-hole package. This device is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement. The FQL40N50 is designed for high-voltage switching applications requiring 500V drain-to-source voltage capability with 40A continuous drain current at 25°C.

Key Parameters

Parameter	Value	Unit
Drain to Source Voltage (Vdss)	500	V
Continuous Drain Current (Id) @ 25°C	40	A (Tc)
Rds On (Max) @ Id, Vgs	110 mOhm @ 20A, 10V	mOhm
Gate Charge (Qg) (Max) @ Vgs	200	nC @ 10V
Power Dissipation (Max)	460	W (Tc)
Operating Temperature Range	-55 to 150	°C (TJ)
Package Type	TO-264-3	Through Hole
Vgs (Max)	±30	V

Substitute Part Grouping Explanation

Substitution of the FQL40N50 is determined by the following critical electrical and mechanical parameters:

Primary Substitution Criteria:

Drain to Source Voltage (Vdss): Must equal or exceed 500V
Continuous Drain Current (Id): Must equal or exceed 40A at 25°C
Gate Drive Voltage: Compatible with 10V drive capability
Package Type: Through-hole mounting (TO-264-3, TO-264AA, or PLUS264™)
Operating Temperature Range: Must support -55°C to 150°C

Secondary Compatibility Factors:

Rds On (Max): Lower or equal values indicate improved performance
Gate Charge (Qg): Lower values reduce drive circuit complexity
Power Dissipation: Higher ratings provide thermal margin
Vgs (Max): Must accommodate ±30V or greater

Substitute parts are grouped into two categories: manufacturer-recommended alternatives and similar performance devices from alternative suppliers. All listed substitutes maintain N-Channel MOSFET technology with through-hole mounting and meet or exceed the primary electrical specifications of the FQL40N50.

Parameter Comparison

Parameter	FQL40N50	NTHL099N60S5	IXFK44N50P	IXFK48N50	IXFK48N50Q	IXFK80N50P	IXTB62N50L
Manufacturer	onsemi	onsemi	IXYS	IXYS	IXYS	IXYS	IXYS
Vdss (V)	500	600	500	500	500	500	500
Id @ 25°C (A)	40	33	44	48	48	80	62
Rds On (Max) (mOhm)	110 @ 20A, 10V	99 @ 13.5A, 10V	140 @ 22A, 10V	100 @ 24A, 10V	100 @ 24A, 10V	65 @ 40A, 10V	100 @ 31A, 20V
Gate Charge Qg (nC)	200 @ 10V	48 @ 10V	98 @ 10V	270 @ 10V	190 @ 10V	197 @ 10V	550 @ 20V
Power Dissipation (W)	460	184	658	500	500	1040	800
Operating Temp (°C)	-55 to 150	-55 to 150	-55 to 150	-55 to 150	-55 to 150	-55 to 150	-55 to 150
Package	TO-264-3	TO-247-3	TO-264AA	TO-264AA	TO-264AA	TO-264AA	PLUS264™
Vgs (Max) (V)	±30	±30	±30	±20	±20	±30	±30
Product Status	Obsolete	Not For New Designs	Active	Active	Active	Active	Active

Engineering Selection Recommendations

Manufacturer-Recommended Substitute:

The NTHL099N60S5 (onsemi SuperFET® V series) is the manufacturer-recommended alternative. This device provides 600V Vdss capability, exceeding the FQL40N50 specification. However, the continuous drain current is reduced to 33A, which falls below the 40A requirement of the original part. The NTHL099N60S5 is classified as "Not For New Designs," indicating limited long-term availability. This substitute is suitable only for applications where the 33A current rating is acceptable and higher voltage margin is beneficial.

Primary Active Substitutes (IXYS HiPerFET™ Series):

The IXFK44N50P, IXFK48N50, IXFK48N50Q, and IXFK80N50P are all active products from IXYS with 500V Vdss matching the FQL40N50 specification. All four devices exceed the 40A continuous drain current requirement:

IXFK44N50P: 44A rating with 658W power dissipation. Gate charge of 98 nC is lower than the FQL40N50, reducing drive circuit stress. Mounted in TO-264AA package. RoHS3 compliant with MSL 1.
IXFK48N50: 48A rating with 500W power dissipation. Gate charge of 270 nC is higher than the FQL40N50, requiring higher drive capability. Vgs (Max) is ±20V, which is lower than the FQL40N50 specification of ±30V. Mounted in TO-264AA package. RoHS3 compliant with MSL 1.
IXFK48N50Q: 48A rating with 500W power dissipation. Q-Class variant with 190 nC gate charge, providing better drive characteristics than IXFK48N50. Vgs (Max) is ±20V. Mounted in TO-264AA package. RoHS3 compliant with MSL 1.
IXFK80N50P: 80A rating with 1040W power dissipation. Provides the highest current capability and thermal margin. Gate charge of 197 nC and Rds On of 65 mOhm represent superior performance characteristics. Mounted in TO-264AA package. RoHS3 compliant with MSL 1.

Alternative Substitute (IXYS Linear Series):

The IXTB62N50L provides 62A continuous drain current with 800W power dissipation. This device operates with 20V drive voltage (versus 10V for the FQL40N50), requiring different gate drive circuit design. Gate charge of 550 nC is significantly higher, increasing drive circuit complexity. Mounted in PLUS264™ package. RoHS3 compliant with MSL 1.

Compliance and Certification:

All substitute parts are RoHS3 compliant and REACH unaffected. All devices operate across the -55°C to 150°C temperature range matching the FQL40N50. Package compatibility varies: TO-264AA and PLUS264™ packages are mechanically similar to TO-264-3 but require PCB layout verification. The TO-247-3 package (NTHL099N60S5) has different pin spacing and requires board redesign.

Frequently Asked Questions (FAQ)

Q: Can the NTHL099N60S5 directly replace the FQL40N50?

A: The NTHL099N60S5 has higher voltage rating (600V vs. 500V) but lower current rating (33A vs. 40A). Direct replacement is not suitable for applications requiring the full 40A continuous current. Additionally, the TO-247-3 package differs from the TO-264-3, requiring PCB layout changes.

Q: Which substitute provides the best performance match to the FQL40N50?

A: The IXFK44N50P matches the 500V voltage specification exactly and provides 44A current capability, exceeding the 40A requirement by 10%. Gate charge of 98 nC is lower than the FQL40N50 (200 nC), reducing drive circuit stress. The TO-264AA package is mechanically compatible with TO-264-3 layouts.

Q: What is the difference between IXFK48N50 and IXFK48N50Q?

A: Both devices provide 48A continuous current and 500W power dissipation at 500V. The IXFK48N50Q is a Q-Class variant with lower gate charge (190 nC vs. 270 nC), providing improved switching characteristics and reduced drive circuit requirements. Both have Vgs (Max) of ±20V, which is lower than the FQL40N50 specification of ±30V.

Q: Is the IXFK80N50P suitable for applications requiring only 40A?

A: Yes. The IXFK80N50P provides 80A continuous current, well above the 40A requirement. The device offers superior thermal performance (1040W vs. 460W) and lower Rds On (65 mOhm vs. 110 mOhm), making it suitable for applications where thermal margin and efficiency are priorities. The higher current rating does not create compatibility issues in lower-current applications.

Q: What are the package compatibility considerations?

A: The FQL40N50 uses TO-264-3 package. Substitutes IXFK44N50P, IXFK48N50, IXFK48N50Q, and IXFK80N50P use TO-264AA package, which is mechanically similar with compatible pin spacing. The IXTB62N50L uses PLUS264™ package, also compatible with TO-264-3 layouts. The NTHL099N60S5 uses TO-247-3 package with different pin spacing, requiring PCB redesign.

Q: Does the IXTB62N50L require different gate drive circuitry?

A: Yes. The IXTB62N50L operates with 20V drive voltage compared to the FQL40N50 specification of 10V. Additionally, gate charge is 550 nC at 20V, significantly higher than the FQL40N50 (200 nC at 10V). Gate drive circuit redesign is necessary to accommodate these specifications.

Q: Are all substitute parts RoHS3 compliant?

A: Yes. All listed substitute parts are RoHS3 compliant and REACH unaffected, matching the compliance status of the FQL40N50.

Q: What is the product status of each substitute?

A: IXFK44N50P, IXFK48N50, IXFK48N50Q, IXFK80N50P, and IXTB62N50L are all active products with ongoing availability. The NTHL099N60S5 is classified as "Not For New Designs," indicating limited future availability and suitability only for legacy system support.

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