IRF840LCS N-Channel MOSFET 500V 8A Equivalent & Substitute Parts

Part Overview

The IRF840LCS 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, making equivalent and substitute parts necessary for new designs and ongoing production requirements. The IRF840LCS remains in stock inventory with 2200 units available, but active alternatives with improved specifications and current manufacturing status are available for design flexibility and supply chain continuity.

Key Parameters

Parameter	Value	Unit
FET Type	N-Channel	—
Drain to Source Voltage (Vdss)	500	V
Continuous Drain Current (Id) @ 25°C	8	A (Tc)
Drive Voltage (Max Rds On)	10	V
Rds On (Max) @ Id, Vgs	850	mOhm @ 4.8A, 10V
Gate Threshold Voltage Vgs(th) (Max) @ Id	4	V @ 250µA
Gate Charge (Qg) (Max) @ Vgs	39	nC @ 10V
Maximum Gate Voltage Vgs (Max)	±30	V
Input Capacitance (Ciss) (Max) @ Vds	1100	pF @ 25V
Power Dissipation (Max)	3.1 (Ta), 125 (Tc)	W
Operating Temperature Range	-55 to 150	°C (TJ)
Mounting Type	Surface Mount	—
Package / Case	TO-263-3, D2PAK	—
Product Status	Obsolete	—
RoHS Status	Non-compliant	—

Substitute Part Grouping Explanation

Substitution of the IRF840LCS is determined by strict adherence to the following electrical and mechanical parameters:

Primary Substitution Criteria:

Drain to Source Voltage (Vdss): 500V minimum
Continuous Drain Current (Id): 8A minimum at 25°C
Gate Threshold Voltage (Vgs(th)): 4V maximum
Maximum Gate Voltage (Vgs): ±30V
Operating Temperature Range: -55°C to 150°C minimum
Mounting Type: Surface Mount
Package: TO-263 (D2PAK) compatible footprint

Secondary Compatibility Parameters:

Rds On (Max): 850mOhm or lower at specified conditions
Gate Charge (Qg): 39nC or lower at 10V
Input Capacitance (Ciss): 1100pF or lower at 25V

Substitute parts are grouped into two categories: parametric equivalents (identical electrical specifications) and manufacturer-recommended alternatives (enhanced specifications within the same voltage and current class).

Parameter Comparison

Parameter	IRF840LCS	IRF840LCSPBF	STB11NK50ZT4	Unit
Manufacturer	Vishay Siliconix	Vishay Siliconix	STMicroelectronics	—
FET Type	N-Channel	N-Channel	N-Channel	—
Vdss	500	500	500	V
Continuous Drain Current (Id) @ 25°C	8	8	10	A (Tc)
Drive Voltage (Max Rds On)	10	10	10	V
Rds On (Max) @ Id, Vgs	850 @ 4.8A, 10V	850 @ 4.8A, 10V	520 @ 4.5A, 10V	mOhm
Vgs(th) (Max) @ Id	4 @ 250µA	4 @ 250µA	4.5 @ 100µA	V
Gate Charge (Qg) (Max) @ Vgs	39 @ 10V	39 @ 10V	68 @ 10V	nC
Vgs (Max)	±30	±30	±30	V
Input Capacitance (Ciss) (Max) @ Vds	1100 @ 25V	1100 @ 25V	1390 @ 25V	pF
Power Dissipation (Max)	3.1 (Ta), 125 (Tc)	3.1 (Ta), 125 (Tc)	125 (Tc)	W
Operating Temperature	-55 to 150	-55 to 150	-55 to 150	°C (TJ)
Mounting Type	Surface Mount	Surface Mount	Surface Mount	—
Package / Case	TO-263-3, D2PAK	TO-263-3, D2PAK	TO-263-3, D2PAK	—
Product Status	Obsolete	Active	Active	—
RoHS Status	Non-compliant	ROHS3 Compliant	ROHS3 Compliant	—
Moisture Sensitivity Level (MSL)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	—

Engineering Selection Recommendations

IRF840LCSPBF (Parametric Equivalent)

The IRF840LCSPBF is a direct parametric equivalent to the IRF840LCS, manufactured by Vishay Siliconix with identical electrical specifications. This part differs only in packaging format (Tube versus standard packaging) and product status (Active versus Obsolete). The IRF840LCSPBF carries ROHS3 compliance certification, addressing regulatory requirements that the original IRF840LCS does not meet. With 4025 units in stock inventory, this part provides immediate supply availability and is suitable for applications requiring exact electrical performance matching. Selection of IRF840LCSPBF is appropriate for designs where regulatory compliance and supply continuity are primary concerns while maintaining identical electrical characteristics.

STB11NK50ZT4 (Manufacturer-Recommended Alternative)

The STB11NK50ZT4, manufactured by STMicroelectronics, is a manufacturer-recommended substitute offering enhanced electrical performance within the same voltage and current class. This device provides 10A continuous drain current (versus 8A), lower on-resistance (520mOhm versus 850mOhm), and improved thermal performance. The STB11NK50ZT4 is rated as Active with ROHS3 compliance and carries SuperMESH™ technology designation. With 4361 units in stock, this part is suitable for applications where improved efficiency and thermal characteristics provide design advantages. The higher gate charge (68nC versus 39nC) and input capacitance (1390pF versus 1100pF) require verification of gate drive circuit compatibility. Selection of STB11NK50ZT4 is appropriate for new designs or redesigns where performance enhancement and regulatory compliance are required.

Frequently Asked Questions (FAQ)

Q: Can IRF840LCSPBF be used as a direct replacement for IRF840LCS?

A: Yes. The IRF840LCSPBF is a parametric equivalent with identical electrical specifications: 500V Vdss, 8A continuous drain current, 850mOhm Rds On, 39nC gate charge, and 1100pF input capacitance. The parts are electrically interchangeable in all applications. The primary difference is product status (Active versus Obsolete) and RoHS compliance (ROHS3 Compliant versus Non-compliant).

Q: What are the key differences between IRF840LCS and STB11NK50ZT4?

A: The STB11NK50ZT4 provides enhanced performance: 10A continuous drain current (versus 8A), lower on-resistance of 520mOhm (versus 850mOhm), and improved thermal efficiency. Both devices share identical 500V Vdss rating, ±30V gate voltage rating, and -55°C to 150°C operating temperature range. The STB11NK50ZT4 has higher gate charge (68nC versus 39nC) and input capacitance (1390pF versus 1100pF), requiring gate drive circuit evaluation.

Q: Are all three parts compatible with the same PCB footprint?

A: Yes. All three parts use the TO-263-3 (D2PAK) package with identical pinout and mechanical dimensions. PCB footprints designed for IRF840LCS are directly compatible with IRF840LCSPBF and STB11NK50ZT4 without layout modifications.

Q: Which substitute part should be selected for new designs?

A: For new designs, IRF840LCSPBF or STB11NK50ZT4 are both suitable. IRF840LCSPBF maintains exact electrical specifications with improved regulatory compliance. STB11NK50ZT4 provides enhanced performance characteristics (higher current rating, lower on-resistance) with ROHS3 compliance. Selection depends on whether exact specification matching or performance enhancement is prioritized.

Q: What is the impact of higher gate charge in STB11NK50ZT4?

A: The STB11NK50ZT4 gate charge of 68nC (versus 39nC in IRF840LCS) requires higher gate drive current or longer switching times. Gate drive circuits must be evaluated to confirm adequate drive capability. Higher gate charge may increase switching losses in high-frequency applications.

Q: Are all three parts RoHS compliant?

A: IRF840LCS is RoHS non-compliant. Both IRF840LCSPBF and STB11NK50ZT4 are ROHS3 compliant. For applications requiring regulatory compliance with RoHS directives, IRF840LCSPBF or STB11NK50ZT4 must be selected.

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

A: All three parts carry Moisture Sensitivity Level (MSL) rating of 1 (Unlimited), indicating no moisture sensitivity restrictions for storage, handling, or reflow processes.

Q: Can STB11NK50ZT4 be used in applications designed for 8A maximum current?

A: Yes. The STB11NK50ZT4 is rated for 10A continuous drain current, providing margin above the 8A requirement. The lower on-resistance (520mOhm versus 850mOhm) results in reduced power dissipation and improved thermal performance in 8A applications.

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