IXFK44N50 N-Channel MOSFET 500V 44A Equivalent & Substitute Parts

Part Overview

The IXFK44N50 is an N-Channel MOSFET manufactured by IXYS, rated for 500V drain-to-source voltage with 44A continuous drain current at 25°C. This device is housed in a TO-264AA through-hole package and is part of the HiPerFET™ series. The IXFK44N50 is classified as obsolete, making identification of functionally equivalent substitute parts essential for ongoing design support, maintenance, and production continuity.

Key Parameters

Parameter	Value	Unit
FET Type	N-Channel	—
Drain to Source Voltage (Vdss)	500	V
Continuous Drain Current (Id) @ 25°C	44	A
Drive Voltage (Max Rds On)	10	V
Rds On (Max) @ Id, Vgs	120 mOhm @ 22A, 10V	—
Power Dissipation (Max)	500	W
Operating Temperature Range	-55 to 150	°C
Mounting Type	Through Hole	—
Package	TO-264AA	—

Substitute Part Grouping Explanation

Substitution of the IXFK44N50 is determined by the following critical electrical and mechanical parameters:

Voltage Rating: The substitute must maintain the 500V Vdss specification to ensure safe operation in the same circuit topology.

Current Rating: The substitute must support a continuous drain current of 40A or greater at 25°C to handle the design load without thermal derating.

On-State Resistance (Rds On): The substitute must not exceed 120 mOhm at the specified gate-source voltage and current conditions to maintain acceptable power dissipation and thermal performance.

Package Compatibility: The substitute must be compatible with TO-264-3 or TO-264AA through-hole mounting to ensure mechanical fit and thermal interface compatibility.

Operating Temperature Range: The substitute must support the full -55°C to 150°C junction temperature range.

The FQL40N50F from onsemi meets these substitution criteria with equivalent voltage and temperature ratings, compatible through-hole packaging, and comparable on-state resistance characteristics.

Parameter Comparison

Parameter	IXFK44N50 (Main Part)	FQL40N50F (Substitute)	Unit
Manufacturer	IXYS	onsemi	—
FET Type	N-Channel	N-Channel	—
Drain to Source Voltage (Vdss)	500	500	V
Continuous Drain Current (Id) @ 25°C	44	40	A
Drive Voltage (Max Rds On)	10	10	V
Rds On (Max) @ Id, Vgs	120 mOhm @ 22A, 10V	110 mOhm @ 20A, 10V	—
Gate Charge (Qg) (Max) @ Vgs	270 nC @ 10V	200 nC @ 10V	—
Input Capacitance (Ciss) (Max) @ Vds	8400 pF @ 25V	7500 pF @ 25V	—
Power Dissipation (Max)	500	460	W
Operating Temperature Range	-55 to 150	-55 to 150	°C
Mounting Type	Through Hole	Through Hole	—
Package	TO-264AA	TO-264-3	—
Product Status	Obsolete	Obsolete	—
RoHS Status	RoHS non-compliant	ROHS3 Compliant	—

Engineering Selection Recommendations

Primary Substitute: The FQL40N50F is the qualified substitute for the IXFK44N50. Both devices are obsolete, requiring careful inventory management and long-term sourcing strategy.

Compliance Consideration: The FQL40N50F carries ROHS3 compliance, whereas the IXFK44N50 is RoHS non-compliant. This distinction is relevant for applications subject to RoHS regulatory requirements.

Current Derating: The FQL40N50F is rated for 40A continuous drain current compared to the IXFK44N50's 44A rating. Applications operating near the 44A limit require thermal analysis to confirm the 40A substitute remains within acceptable junction temperature limits.

On-State Resistance: The FQL40N50F exhibits lower on-state resistance (110 mOhm vs. 120 mOhm), resulting in reduced conduction losses and improved thermal performance in equivalent applications.

Package Compatibility: Both devices use compatible TO-264 through-hole packages (TO-264AA and TO-264-3), ensuring mechanical and thermal interface compatibility with existing PCB designs.

Frequently Asked Questions (FAQ)

Q: Can the FQL40N50F directly replace the IXFK44N50 in all applications?

A: The FQL40N50F is electrically compatible for applications where the continuous drain current requirement does not exceed 40A. The 4A reduction in current rating requires verification that thermal and load conditions remain within acceptable limits. Both devices share identical 500V voltage ratings, compatible through-hole packaging, and matching operating temperature ranges.

Q: What is the significance of the different current ratings (44A vs. 40A)?

A: The IXFK44N50 supports 44A continuous drain current, while the FQL40N50F supports 40A. For designs operating below 40A, this difference is not limiting. For designs requiring 40A to 44A, thermal analysis must confirm that the FQL40N50F's lower power dissipation rating (460W vs. 500W) does not cause junction temperature to exceed 150°C under worst-case conditions.

Q: Are the TO-264AA and TO-264-3 packages mechanically interchangeable?

A: Yes. Both packages are TO-264 variants with three leads and compatible through-hole mounting footprints. The packages are mechanically and thermally interchangeable on standard PCB designs.

Q: What is the impact of the lower gate charge in the FQL40N50F?

A: The FQL40N50F has lower gate charge (200 nC vs. 270 nC), resulting in faster switching transitions and reduced gate drive power requirements. This is a performance advantage in high-frequency switching applications.

Q: Why is RoHS compliance status different between these parts?

A: The IXFK44N50 predates RoHS3 requirements and is non-compliant. The FQL40N50F is ROHS3 compliant, making it suitable for applications subject to RoHS regulatory frameworks. Both devices are REACH unaffected and classified under ECCN EAR99.

Q: Are both parts truly obsolete?

A: Yes. Both the IXFK44N50 and FQL40N50F are classified as obsolete products. Inventory availability is limited, and long-term sourcing should be evaluated. Current inventory levels are 1385 pcs for IXFK44N50 and 18700 pcs for FQL40N50F.

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