IXFH21N50F N-Channel 500V 21A MOSFET Equivalent & Substitute Parts

Part Overview

The IXFH21N50F is an N-Channel MOSFET manufactured by IXYS, rated for 500V drain-to-source voltage with 21A continuous drain current at 25°C. This device is packaged in TO-247 (IXFH) configuration and is designed for high-voltage switching applications requiring 300W power dissipation capability. The part is currently classified as obsolete, making identification of functionally equivalent active alternatives necessary for ongoing design support and procurement.

Key Parameters

Parameter	Value	Unit
Drain-to-Source Voltage (Vdss)	500	V
Continuous Drain Current (Id) @ 25°C	21	A
On-State Resistance (Rds On Max) @ 10.5A, 10V	250	mOhm
Gate Threshold Voltage (Vgs(th) Max) @ 4mA	5.5	V
Gate Charge (Qg Max) @ 10V	77	nC
Input Capacitance (Ciss Max) @ 25V	2600	pF
Power Dissipation (Max)	300	W
Operating Temperature Range	-55 to 150	°C
Mounting Type	Through Hole
Package	TO-247-3
FET Technology	MOSFET (Metal Oxide)

Substitute Part Grouping Explanation

Substitution of the IXFH21N50F is determined by strict equivalence across the following critical parameters:

Mandatory Matching Parameters:

Drain-to-Source Voltage (Vdss): 500V minimum
Mounting Type: Through Hole
Package Type: TO-247-3 compatible
FET Type: N-Channel
Technology: MOSFET (Metal Oxide)

Functional Compatibility Parameters:

Continuous Drain Current (Id): Must equal or exceed 21A at 25°C
On-State Resistance (Rds On): Must not exceed 250mOhm at specified gate voltage
Gate Threshold Voltage (Vgs(th)): Must be within ±20V gate voltage specification
Operating Temperature: Must support -55°C to 150°C range
Power Dissipation: Must support minimum 300W thermal capability

The two substitute parts listed below meet all mandatory matching parameters and functional compatibility requirements.

Parameter Comparison

Parameter	IXFH21N50F (Main)	STW20NM50FD	STW20NK50Z	Unit
Manufacturer	IXYS	STMicroelectronics	STMicroelectronics
Drain-to-Source Voltage (Vdss)	500	500	500	V
Continuous Drain Current (Id) @ 25°C	21	20	17	A
On-State Resistance (Rds On Max) @ 10V	250 @ 10.5A	250 @ 10A	270 @ 8.5A	mOhm
Gate Threshold Voltage (Vgs(th) Max)	5.5 @ 4mA	5 @ 250µA	4.5 @ 100µA	V
Gate Charge (Qg Max) @ 10V	77	53	119	nC
Input Capacitance (Ciss Max) @ 25V	2600	1380	2600	pF
Power Dissipation (Max)	300	214	190	W
Operating Temperature (TJ)	-55 to 150	-55 to 150	-55 to 150	°C
Package	TO-247-3	TO-247-3	TO-247-3
Product Status	Obsolete	Active	Active
RoHS Status	Not specified	ROHS3 Compliant	Not specified

Engineering Selection Recommendations

STW20NM50FD (Primary Substitute): This part is recommended as the primary substitute for the IXFH21N50F. It maintains identical Vdss (500V) and equivalent Rds On (250mOhm) specifications. The continuous drain current rating of 20A is within 95% of the original 21A specification. The part is manufactured by STMicroelectronics with active product status and ROHS3 compliance, ensuring long-term availability and regulatory alignment. Power dissipation of 214W is lower than the original 300W, requiring thermal design verification for applications operating at maximum power levels.

STW20NK50Z (Secondary Substitute): This part provides an alternative substitute with identical Vdss (500V) and compatible TO-247-3 packaging. The continuous drain current of 17A represents an 81% rating relative to the original specification. On-state resistance of 270mOhm is slightly elevated compared to the original 250mOhm. Power dissipation of 190W is significantly lower than the original 300W. This part is suitable for applications with reduced current and thermal requirements. Active product status and STMicroelectronics manufacturing ensure availability.

Both substitute parts are manufactured by STMicroelectronics, an established supplier with active product lines, addressing the obsolescence of the original IXYS component.

Frequently Asked Questions (FAQ)

Q: Can STW20NM50FD directly replace IXFH21N50F in all applications?

A: STW20NM50FD meets the critical electrical parameters (Vdss, Rds On, package) for direct substitution in most applications. However, the reduced power dissipation rating (214W vs. 300W) requires verification that thermal design does not exceed this limit. The 20A current rating (vs. 21A original) is acceptable for most designs but should be confirmed against circuit requirements.

Q: What is the difference between STW20NM50FD and STW20NK50Z?

A: Both parts share identical Vdss (500V) and TO-247-3 packaging. STW20NM50FD offers superior current handling (20A vs. 17A) and lower on-state resistance (250mOhm vs. 270mOhm), making it the preferred choice for higher-current applications. STW20NK50Z is suitable for lower-current designs with reduced thermal requirements.

Q: Are the substitute parts pin-compatible with IXFH21N50F?

A: Yes. Both STW20NM50FD and STW20NK50Z use TO-247-3 packaging with identical pin configuration (Gate, Drain, Source) to the IXFH21N50F. Direct PCB mounting without layout modification is possible.

Q: What compliance certifications apply to the substitute parts?

A: STW20NM50FD carries ROHS3 compliance and REACH Unaffected status. Both parts are classified under ECCN EAR99 and HTSUS 8541.29.0095, matching the regulatory classification of the original part.

Q: Why is the power dissipation lower in the substitute parts?

A: The substitute parts employ different semiconductor technologies (FDmesh™ and SuperMESH™) compared to the original HiPerRF™ series. These technologies optimize for lower on-state resistance and gate charge at the trade-off of reduced absolute power dissipation ratings. Thermal design must account for this specification difference.

Q: Can I use STW20NK50Z if my application requires 21A continuous current?

A: No. STW20NK50Z is rated for 17A continuous drain current, which is below the 21A requirement. Use STW20NM50FD (20A rating) or verify that actual circuit current does not exceed 17A before selecting this part.

Q: What is the moisture sensitivity level for these parts?

A: All three parts (IXFH21N50F, STW20NM50FD, STW20NK50Z) carry MSL 1 (Unlimited) classification, indicating no moisture sensitivity restrictions for storage or handling.

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