IRF840STRL Equivalent & Substitute Parts

Part Overview

The IRF840STRL is an N-Channel MOSFET manufactured by Vishay Siliconix, rated for 500V drain-to-source voltage with 8A continuous drain current in a surface mount TO-263 (D2PAK) package. This device is classified as obsolete, which necessitates identification of equivalent and substitute components for ongoing design support and procurement.

The IRF840STRL serves in high-voltage switching applications requiring moderate current handling and low on-resistance characteristics. Due to its obsolete status, alternative parts with matching or superior electrical specifications are required to maintain design continuity and ensure component availability.

Key Parameters

Parameter	Value	Unit
Drain to Source Voltage (Vdss)	500	V
Continuous Drain Current (Id) @ 25°C	8	A (Tc)
On-Resistance (Rds On Max) @ 4.8A, 10V	850	mOhm
Gate Threshold Voltage (Vgs(th) Max) @ 250µA	4	V
Gate Charge (Qg Max) @ 10V	63	nC
Input Capacitance (Ciss Max) @ 25V	1300	pF
Power Dissipation (Max)	3.1 (Ta), 125 (Tc)	W
Operating Temperature Range	-55 to 150	°C (TJ)
Mounting Type	Surface Mount	—
Package	TO-263 (D2PAK)	—

Substitute Part Grouping Explanation

Substitution of the IRF840STRL is determined by the following critical electrical and mechanical parameters:

Primary Matching Criteria:

Drain-to-Source Voltage (Vdss): 500V minimum
Package Type: TO-263 (D2PAK) surface mount configuration
Operating Temperature Range: -55°C to 150°C
FET Technology: N-Channel MOSFET (Metal Oxide)

Secondary Compatibility Factors:

Continuous Drain Current (Id): Equal to or greater than 8A
On-Resistance (Rds On): Equal to or lower than 850 mOhm at specified conditions
Gate Threshold Voltage (Vgs(th)): Within acceptable switching characteristics
Gate Charge (Qg): Comparable for driver circuit compatibility
Input Capacitance (Ciss): Similar for circuit timing considerations

Substitute parts must maintain electrical performance within the application's design margins while meeting the same package and thermal specifications. Parts listed as Active or with current RoHS3 compliance provide superior long-term availability compared to the obsolete IRF840STRL.

Parameter Comparison

Parameter	IRF840STRL	IRF840STRLPBF	STB11NK50ZT4	Unit
Manufacturer	Vishay Siliconix	Vishay Siliconix	STMicroelectronics	—
Product Status	Obsolete	Active	Active	—
Drain to Source Voltage (Vdss)	500	500	500	V
Continuous Drain Current (Id) @ 25°C	8	8	10	A (Tc)
On-Resistance (Rds On Max)	850 @ 4.8A, 10V	850 @ 4.8A, 10V	520 @ 4.5A, 10V	mOhm
Gate Threshold Voltage (Vgs(th) Max)	4 @ 250µA	4 @ 250µA	4.5 @ 100µA	V
Gate Charge (Qg Max) @ 10V	63	63	68	nC
Input Capacitance (Ciss Max) @ 25V	1300	1300	1390	pF
Power Dissipation (Max)	3.1 (Ta), 125 (Tc)	3.1 (Ta), 125 (Tc)	125 (Tc)	W
Operating Temperature Range	-55 to 150	-55 to 150	-55 to 150	°C (TJ)
Package	TO-263 (D2PAK)	TO-263 (D2PAK)	TO-263 (D2PAK)	—
RoHS Status	Non-compliant	ROHS3 Compliant	ROHS3 Compliant	—
Moisture Sensitivity Level (MSL)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	—

Engineering Selection Recommendations

IRF840STRLPBF (Vishay Siliconix)

The IRF840STRLPBF is a direct electrical equivalent to the IRF840STRL with identical electrical specifications. This part is classified as Active with current availability and carries ROHS3 compliance certification. The primary distinction is packaging format (Tape & Reel versus bulk), making this the preferred direct replacement for obsolete IRF840STRL applications. Electrical performance, thermal characteristics, and package dimensions remain unchanged, ensuring pin-for-pin compatibility without circuit redesign.

STB11NK50ZT4 (STMicroelectronics)

The STB11NK50ZT4 represents an enhanced substitute with superior electrical performance characteristics. This device provides 10A continuous drain current compared to 8A in the IRF840STRL, with significantly lower on-resistance (520 mOhm versus 850 mOhm). The STB11NK50ZT4 maintains identical 500V voltage rating and TO-263 (D2PAK) package configuration. Higher gate threshold voltage (4.5V versus 4V) and marginally increased gate charge (68 nC versus 63 nC) remain within acceptable design tolerances for most applications. This part is Active with ROHS3 compliance and represents a performance upgrade suitable for applications requiring improved efficiency or higher current capability within the same thermal envelope.

Both substitute parts maintain the -55°C to 150°C operating temperature range and MSL 1 moisture sensitivity rating. Selection between IRF840STRLPBF and STB11NK50ZT4 depends on whether direct electrical equivalence or performance enhancement is required for the specific application.

Frequently Asked Questions (FAQ)

Q: Can IRF840STRLPBF be used as a direct replacement for IRF840STRL?

A: Yes. The IRF840STRLPBF is electrically and mechanically identical to the IRF840STRL. Both devices share the same drain-to-source voltage (500V), continuous drain current (8A), on-resistance (850 mOhm), gate charge (63 nC), and TO-263 (D2PAK) package configuration. The primary difference is packaging format (Tape & Reel versus bulk). No circuit modifications are required.

Q: What are the advantages of using STB11NK50ZT4 over IRF840STRLPBF?

A: The STB11NK50ZT4 offers improved electrical performance with 10A continuous drain current (versus 8A) and lower on-resistance of 520 mOhm (versus 850 mOhm). These characteristics reduce power dissipation and heat generation in switching applications. Both parts maintain the same 500V voltage rating and TO-263 package. The STB11NK50ZT4 is suitable for applications requiring higher current handling or improved efficiency.

Q: Are all three parts pin-compatible?

A: Yes. The IRF840STRL, IRF840STRLPBF, and STB11NK50ZT4 all use the TO-263 (D2PAK) package with identical pin configuration (2 leads plus tab). Direct PCB substitution is possible without layout modifications.

Q: What is the difference between IRF840STRL and IRF840STRLPBF packaging?

A: IRF840STRL is supplied in bulk packaging, while IRF840STRLPBF is supplied in Tape & Reel (TR) format. Electrical specifications are identical. Tape & Reel packaging is standard for automated assembly processes.

Q: Does the higher gate threshold voltage of STB11NK50ZT4 affect circuit operation?

A: The STB11NK50ZT4 has a gate threshold voltage of 4.5V compared to 4V in the IRF840STRL. This 0.5V difference is within typical driver circuit tolerances and does not require circuit redesign for most applications. Verify that the gate drive voltage remains adequate for the specific application.

Q: Are all substitute parts RoHS compliant?

A: The IRF840STRL is RoHS non-compliant. Both IRF840STRLPBF and STB11NK50ZT4 are ROHS3 compliant, meeting current environmental and regulatory requirements.

Q: What is the thermal performance difference between these parts?

A: All three parts share identical maximum power dissipation ratings of 125W at Tc (case temperature). Thermal performance depends on PCB layout, heatsinking, and ambient conditions rather than device specifications.

Q: Can STB11NK50ZT4 be used in applications designed for IRF840STRL?

A: Yes. The STB11NK50ZT4 meets or exceeds all critical electrical specifications of the IRF840STRL while maintaining package compatibility. The improved current rating and lower on-resistance make it suitable for existing designs. Verify that the slightly higher gate threshold voltage (4.5V versus 4V) is compatible with the gate drive circuit.

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