FQB10N50CFTM-WS Equivalent & Substitute Parts

Part Overview

The FQB10N50CFTM-WS is an N-Channel 500V 10A MOSFET manufactured by onsemi in the FRFET® and QFET™ series. This device is housed in a TO-263 (D2PAK) surface mount package and is rated for 143W power dissipation at case temperature. The part is classified as obsolete, making identification of equivalent and substitute components necessary for ongoing design support, production continuity, and system maintenance.

Key Parameters

Parameter	Value	Unit
Drain to Source Voltage (Vdss)	500	V
Continuous Drain Current (Id) @ 25°C	10	A
On-State Resistance (Rds On) @ 5A, 10V	610	mOhm
Gate Threshold Voltage (Vgs(th)) @ 250µA	4	V
Gate Charge (Qg) @ 10V	60	nC
Input Capacitance (Ciss) @ 25V	2210	pF
Power Dissipation (Max)	143	W
Operating Temperature Range	-55 to 150	°C
Package Type	TO-263 (D2PAK)	—
FET Type	N-Channel Enhancement Mode	—

Substitute Part Grouping Explanation

Substitution of the FQB10N50CFTM-WS is determined by the following critical parameters:

Voltage Rating: All substitute parts must maintain a Drain to Source Voltage (Vdss) of 500V to ensure compatibility with the original circuit design and voltage stress limits.

Current Rating: The continuous drain current (Id) at 25°C establishes the minimum current-handling capability. Substitutes with equal or higher current ratings are acceptable, as they provide equivalent or improved performance headroom.

On-State Resistance (Rds On): This parameter directly affects power dissipation and thermal performance. Lower Rds On values indicate improved efficiency and reduced heat generation.

Package Type: The TO-263 (D2PAK) surface mount package is mandatory for mechanical and thermal compatibility with existing PCB layouts and thermal management systems.

Operating Temperature Range: All substitutes must support the -55°C to 150°C operating range to maintain functional integrity across the specified environmental conditions.

FET Technology: All candidates are N-Channel enhancement-mode MOSFETs using metal oxide semiconductor technology, ensuring functional equivalence.

Compliance Status: RoHS3 compliance and REACH unaffected status are preferred for regulatory alignment, though active product status takes precedence for long-term availability.

Parameter Comparison

Part Number	Manufacturer	Vdss (V)	Id @ 25°C (A)	Rds On (mOhm)	Vgs(th) (V)	Qg (nC)	Ciss (pF)	Power Diss. (W)	Package	Status
FQB10N50CFTM-WS	onsemi	500	10	610 @ 5A, 10V	4 @ 250µA	60 @ 10V	2210 @ 25V	143	TO-263 (D2PAK)	Obsolete
FDB20N50F	onsemi	500	20	260 @ 10A, 10V	5 @ 250µA	65 @ 10V	3390 @ 25V	250	TO-263 (D2PAK)	Active
IRF840LCSTRL	Vishay Siliconix	500	8	850 @ 4.8A, 10V	4 @ 250µA	39 @ 10V	1100 @ 25V	125	TO-263 (D2PAK)	Active
IXFA12N50P	IXYS	500	12	500 @ 6A, 10V	5.5 @ 1mA	29 @ 10V	1830 @ 25V	200	TO-263 (D2PAK)	Active
IXTA12N50P	IXYS	500	12	500 @ 6A, 10V	5.5 @ 250µA	29 @ 10V	1830 @ 25V	200	TO-263 (D2PAK)	Active
IXTA15N50L2	IXYS	500	15	480 @ 7.5A, 10V	4.5 @ 250µA	123 @ 10V	4080 @ 25V	300	TO-263 (D2PAK)	Active
IXTA6N50D2	IXYS	500	6	500 @ 3A, 0V	Depletion Mode	96 @ 5V	2800 @ 25V	300	TO-263 (D2PAK)	Active
STB11NK50ZT4	STMicroelectronics	500	10	520 @ 4.5A, 10V	4.5 @ 100µA	68 @ 10V	1390 @ 25V	125	TO-263 (D2PAK)	Active

Engineering Selection Recommendations

Primary Recommendation: FDB20N50F (onsemi)

The FDB20N50F is the manufacturer-recommended substitute. Both devices are onsemi products within the same voltage class (500V) and package type (TO-263 D2PAK). The FDB20N50F offers superior electrical performance with a 20A continuous drain current rating and significantly lower on-state resistance (260 mOhm versus 610 mOhm), resulting in reduced power dissipation and improved thermal efficiency. The device is active in production with full RoHS3 compliance and REACH unaffected status, ensuring long-term availability and regulatory alignment.

Secondary Recommendation: STB11NK50ZT4 (STMicroelectronics)

The STB11NK50ZT4 provides a direct current-rating match (10A) with the original FQB10N50CFTM-WS while maintaining identical voltage specifications and package configuration. This device features improved on-state resistance (520 mOhm versus 610 mOhm) and is actively produced with full RoHS3 compliance. The SuperMESH™ technology platform offers enhanced performance characteristics suitable for high-frequency switching applications.

Alternative Options for Higher Current Requirements:

The IXTA12N50P and IXFA12N50P (IXYS) provide 12A continuous drain current with superior on-state resistance (500 mOhm) and are suitable for applications requiring increased current headroom. Both devices maintain 500V voltage rating, TO-263 package compatibility, and active production status with RoHS3 compliance.

The IXTA15N50L2 (IXYS) offers the highest current rating (15A) among active substitutes with the lowest on-state resistance (480 mOhm) and is appropriate for designs requiring maximum thermal margin and efficiency.

Not Recommended:

The IRF840LCSTRL (Vishay Siliconix) is not recommended as a primary substitute due to its lower current rating (8A) and higher on-state resistance (850 mOhm), which provide reduced performance compared to the original device. Additionally, this device is RoHS non-compliant.

The IXTA6N50D2 (IXYS) operates in depletion mode rather than enhancement mode and is not functionally equivalent to the enhancement-mode FQB10N50CFTM-WS.

Frequently Asked Questions (FAQ)

Q: Can the FDB20N50F directly replace the FQB10N50CFTM-WS in existing designs?

A: Yes. The FDB20N50F is the manufacturer-recommended substitute and maintains identical voltage rating (500V), package type (TO-263 D2PAK), and operating temperature range (-55°C to 150°C). The higher current rating (20A versus 10A) and lower on-state resistance provide improved performance without requiring circuit modifications.

Q: What is the difference between the IXFA12N50P and IXTA12N50P?

A: Both devices are manufactured by IXYS with identical electrical specifications: 500V voltage rating, 12A continuous drain current, 500 mOhm on-state resistance, and TO-263 package configuration. The primary difference is the supplier device package designation (TO-263AA IXFA versus TO-263AA standard). Both are functionally equivalent and suitable for substitution.

Q: Why is the IXTA6N50D2 listed but not recommended?

A: The IXTA6N50D2 operates in depletion mode, meaning it conducts current in the absence of a gate voltage. The original FQB10N50CFTM-WS is an enhancement-mode device that requires positive gate voltage to conduct. These operating modes are fundamentally different and not interchangeable in circuit applications.

Q: Does on-state resistance affect circuit performance?

A: Yes. On-state resistance (Rds On) directly determines the voltage drop across the transistor during conduction and the resulting power dissipation. Lower Rds On values reduce heat generation and improve efficiency. The FDB20N50F (260 mOhm) dissipates significantly less power than the original FQB10N50CFTM-WS (610 mOhm) at equivalent current levels.

Q: Are all substitute parts RoHS3 compliant?

A: No. The IRF840LCSTRL is RoHS non-compliant and should not be used in applications requiring regulatory compliance. All other listed substitutes are RoHS3 compliant and REACH unaffected.

Q: What is the significance of gate charge (Qg)?

A: Gate charge represents the total charge required to switch the transistor from off to on state. Lower gate charge values enable faster switching speeds and reduced gate drive power requirements. This parameter is relevant for high-frequency switching applications but does not affect DC operating characteristics.

Q: Can a substitute with higher current rating be used in place of the original?

A: Yes. A substitute with equal or higher current rating provides equivalent or improved current-handling capability. The circuit will operate within safe margins. However, the substitute must maintain the same voltage rating (500V) and package type (TO-263 D2PAK) for compatibility.

Q: What is the importance of input capacitance (Ciss)?

A: Input capacitance affects gate drive circuit design and switching speed. Higher Ciss values require greater gate charge and may necessitate higher gate drive current. This parameter is relevant for circuit optimization but does not prevent substitution if the gate drive circuit is appropriately designed.

Q: Is the STB11NK50ZT4 a direct replacement for the FQB10N50CFTM-WS?

A: Yes. The STB11NK50ZT4 matches the original device in current rating (10A), voltage rating (500V), and package type (TO-263 D2PAK). It offers improved on-state resistance and is actively produced with full compliance certifications, making it a suitable direct replacement.

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