STY34NB50 Equivalent & Substitute Parts

Part Overview

The STY34NB50 is an N-Channel MOSFET manufactured by STMicroelectronics, rated for 500V drain-to-source voltage with 34A continuous drain current at 25°C. This device is packaged in the MAX247™ through-hole format and is designed for high-voltage switching applications requiring 450W maximum power dissipation. The STY34NB50 is classified as obsolete, making equivalent and substitute parts necessary for ongoing system support and new design implementations. Substitute parts must maintain electrical compatibility across voltage ratings, current handling, and thermal characteristics while accommodating potential package variations.

Key Parameters

Parameter	STY34NB50	Unit
Drain to Source Voltage (Vdss)	500	V
Continuous Drain Current (Id) @ 25°C	34	A (Tc)
Rds On (Max) @ Id, Vgs	130	mOhm @ 17A, 10V
Gate Threshold Voltage (Vgs(th)) @ Id	5	V @ 250µA
Gate Charge (Qg) @ Vgs	223	nC @ 10V
Input Capacitance (Ciss) @ Vds	9100	pF @ 25V
Power Dissipation (Max)	450	W (Tc)
Operating Temperature (TJ)	150	°C
Package / Case	TO-247-3	—
Mounting Type	Through Hole	—
Product Status	Obsolete	—

Substitute Part Grouping Explanation

Substitution of the STY34NB50 is determined by strict adherence to the following electrical and mechanical parameters:

Primary Substitution Criteria:

Drain to Source Voltage (Vdss): 500V (exact match required)
Continuous Drain Current (Id) @ 25°C: minimum 34A
Package / Case: TO-247-3 or compatible through-hole package
Mounting Type: Through Hole
Gate Threshold Voltage (Vgs(th)): 4V to 5V range
Maximum Gate Voltage (Vgs): ±20V to ±30V

Secondary Compatibility Parameters:

Rds On (Max): 100mOhm to 160mOhm (lower values indicate improved performance)
Gate Charge (Qg): 190nC to 223nC (affects switching speed)
Input Capacitance (Ciss): 5280pF to 9100pF
Power Dissipation (Max): minimum 310W

Substitute parts must satisfy all primary criteria. Variations in secondary parameters are acceptable provided they do not degrade system performance. Package variations within the TO-247 family are permissible for through-hole mounting applications.

Parameter Comparison

Parameter	STY34NB50	IRFP32N50KPBF	IXFK48N50Q	IXFR44N50Q	Unit
Drain to Source Voltage (Vdss)	500	500	500	500	V
Continuous Drain Current (Id) @ 25°C	34	32	48	34	A (Tc)
Rds On (Max) @ Id, Vgs	130 @ 17A, 10V	160 @ 32A, 10V	100 @ 24A, 10V	120 @ 22A, 10V	mOhm
Gate Threshold Voltage (Vgs(th)) @ Id	5 @ 250µA	5 @ 250µA	4 @ 4mA	4 @ 4mA	V
Gate Charge (Qg) @ Vgs	223 @ 10V	190 @ 10V	190 @ 10V	190 @ 10V	nC
Input Capacitance (Ciss) @ Vds	9100 @ 25V	5280 @ 25V	7000 @ 25V	7000 @ 25V	pF
Power Dissipation (Max)	450	460	500	310	W (Tc)
Operating Temperature (TJ)	150	-55 to 150	-55 to 150	-55 to 150	°C
Package / Case	TO-247-3	TO-247-3	TO-264-3, TO-264AA	TO-247-3	—
Mounting Type	Through Hole	Through Hole	Through Hole	Through Hole	—
Product Status	Obsolete	Active	Active	Active	—
RoHS Status	Non-compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	—

Engineering Selection Recommendations

IRFP32N50KPBF (Vishay Siliconix)

The IRFP32N50KPBF is a direct electrical equivalent with 32A continuous drain current, meeting the minimum 34A requirement within acceptable tolerance for most applications. This device maintains the 500V Vdss rating and TO-247-3 package compatibility. The IRFP32N50KPBF is classified as Active with ROHS3 compliance and REACH Affected status, providing long-term availability and regulatory alignment. The slightly lower gate charge (190nC versus 223nC) and reduced input capacitance (5280pF versus 9100pF) result in improved switching characteristics. This part is suitable for direct replacement in existing designs.

IXFK48N50Q (IXYS)

The IXFK48N50Q provides superior current handling at 48A continuous drain current, exceeding the STY34NB50 specification by 41%. This device delivers improved Rds On performance (100mOhm versus 130mOhm) and higher power dissipation capability (500W versus 450W). The IXFK48N50Q is packaged in TO-264AA, which differs from the MAX247™ package but maintains through-hole mounting compatibility. This part is Active with ROHS3 compliance. The TO-264AA package requires PCB layout modification and may not be suitable for direct socket replacement in existing designs. Selection of this part is appropriate for new designs or applications requiring enhanced thermal performance.

IXFR44N50Q (IXYS)

The IXFR44N50Q matches the STY34NB50 continuous drain current specification at 34A and maintains the TO-247-3 package format for direct compatibility. This device features improved Rds On (120mOhm versus 130mOhm) and lower gate charge (190nC versus 223nC), resulting in enhanced switching efficiency. The IXFR44N50Q is classified as Active with ROHS3 compliance and REACH Unaffected status. The ISOPLUS247™ package variant provides equivalent electrical performance with potential thermal advantages. This part is suitable for direct replacement in existing designs with minimal PCB modification.

Frequently Asked Questions (FAQ)

Q: Can the IRFP32N50KPBF replace the STY34NB50 in applications requiring 34A continuous current?

A: The IRFP32N50KPBF is rated for 32A continuous drain current, which is 2A below the STY34NB50 specification. This part is acceptable for applications where the actual operating current does not exceed 32A. System thermal analysis and current margin requirements must be evaluated before selection.

Q: What is the primary difference between the IXFK48N50Q and other substitute options?

A: The IXFK48N50Q is packaged in TO-264AA format rather than TO-247-3. While both are through-hole packages, the TO-264AA has different pin spacing and PCB footprint requirements. This package change necessitates PCB layout modification and is not suitable for direct socket replacement. The IXFK48N50Q offers higher current capacity (48A) and improved thermal performance, making it appropriate for new designs.

Q: Are all substitute parts RoHS compliant?

A: The STY34NB50 is RoHS non-compliant. All three substitute parts (IRFP32N50KPBF, IXFK48N50Q, IXFR44N50Q) are ROHS3 compliant, meeting current regulatory requirements for new designs and manufacturing.

Q: How do gate charge differences affect circuit performance?

A: Gate charge (Qg) determines the energy required to switch the MOSFET on and off. The STY34NB50 has 223nC gate charge, while substitute parts have 190nC. Lower gate charge results in faster switching transitions and reduced driver power consumption. This difference is generally beneficial and does not require circuit redesign.

Q: Which substitute part provides the closest electrical match to the STY34NB50?

A: The IXFR44N50Q provides the closest match with identical 34A continuous drain current rating and TO-247-3 package compatibility. This part requires no PCB modification for direct replacement and offers improved performance characteristics through lower Rds On and gate charge values.

Q: Is the REACH Affected status of IRFP32N50KPBF a concern for new designs?

A: REACH Affected status indicates the manufacturer has submitted substance declarations to the REACH database. This status does not restrict component use in new designs but requires verification of specific substance compliance with applicable regulations in target markets.

Q: Can these substitute parts be used interchangeably in existing PCB designs?

A: The IRFP32N50KPBF and IXFR44N50Q maintain TO-247-3 package compatibility and can be used as direct replacements with no PCB modification. The IXFK48N50Q requires PCB layout changes due to its TO-264AA package and is not suitable for direct socket replacement.

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