IXRFSM18N50 Equivalent & Substitute Parts

Part Overview

The IXRFSM18N50 is an N-Channel MOSFET rated for 500V drain-to-source voltage with 19A continuous drain current at 25°C. This device is designed for surface mount applications in the 16-SMPD package and is currently classified as obsolete. Due to its obsolete status, identifying functionally compatible substitute parts is essential for design continuity, production support, and long-term system reliability. The IXRFSM18N50 remains available in inventory (890 pcs), but alternative solutions ensure access to active product lines with extended lifecycle support.

Key Parameters

Parameter	Value	Unit
Drain-to-Source Voltage (Vdss)	500	V
Continuous Drain Current (Id) @ 25°C	19	A
On-State Resistance (Rds On Max) @ Id, Vgs	340 mOhm @ 9.5A, 20V	mOhm
Gate Threshold Voltage (Vgs(th) Max) @ Id	6.5	V @ 250µA
Gate Charge (Qg Max) @ Vgs	42	nC @ 10V
Input Capacitance (Ciss Max) @ Vds	2250	pF @ 400V
Power Dissipation (Max)	835	W
Operating Temperature Range	-55 to 150	°C (TJ)
Mounting Type	Surface Mount
Package	16-BESOP (0.790", 20.11mm Width)

Substitute Part Grouping Explanation

Substitution of the IXRFSM18N50 is evaluated based on the following critical electrical and mechanical parameters:

Voltage Rating Compatibility: The substitute part must support the application's maximum drain-to-source voltage requirement. The IXRFSM18N50 operates at 500V Vdss. Substitute parts with equal or higher voltage ratings are acceptable.

Current Handling Capacity: The continuous drain current rating must meet or exceed the application's current demand. The IXRFSM18N50 provides 19A at 25°C. Substitute parts with equal or higher current ratings are acceptable.

On-State Resistance (Rds On): This parameter directly affects power dissipation and thermal performance. Lower Rds On values indicate improved efficiency. Substitutes with comparable or lower Rds On values are acceptable.

Gate Charge and Input Capacitance: These parameters influence switching speed and gate drive requirements. Substitutes with similar or lower values maintain compatible drive circuit performance.

Thermal Performance: Power dissipation capability must support the application's thermal environment. Substitutes with equal or higher power dissipation ratings are acceptable.

Package and Mounting: Surface mount compatibility and lead configuration must align with PCB design constraints.

Product Status and Compliance: Active product status ensures long-term availability and support. RoHS and REACH compliance certifications provide regulatory assurance.

Parameter Comparison

Parameter	IXRFSM18N50	IXFT50N85XHV	Compatibility Notes
Manufacturer	IXYS-RF	IXYS	Same manufacturer family
FET Type	N-Channel	N-Channel	Identical
Technology	MOSFET (Metal Oxide)	MOSFET (Metal Oxide)	Identical
Drain-to-Source Voltage (Vdss)	500 V	850 V	Substitute rated higher; acceptable for 500V applications
Continuous Drain Current (Id) @ 25°C	19 A	50 A	Substitute rated higher; acceptable for 19A applications
Rds On (Max) @ Id, Vgs	340 mOhm @ 9.5A, 20V	105 mOhm @ 500mA, 10V	Substitute has lower Rds On; improved efficiency
Gate Threshold Voltage (Vgs(th) Max) @ Id	6.5 V @ 250µA	5.5 V @ 4mA	Substitute has lower threshold; compatible gate drive
Gate Charge (Qg Max) @ Vgs	42 nC @ 10V	152 nC @ 10V	Substitute requires higher gate charge; verify gate drive capability
Vgs (Max)	±20 V	±30 V	Substitute rated higher; acceptable
Input Capacitance (Ciss Max) @ Vds	2250 pF @ 400V	4480 pF @ 25V	Substitute has higher capacitance; verify gate drive performance
Power Dissipation (Max)	835 W	890 W (Tc)	Substitute rated higher; acceptable
Operating Temperature Range	-55 to 150 °C (TJ)	-55 to 150 °C (TJ)	Identical
Mounting Type	Surface Mount	Surface Mount	Identical
Package	16-BESOP (0.790", 20.11mm Width)	TO-268-3, D³Pak (2 Leads + Tab)	Different package; PCB layout modification required
Product Status	Obsolete	Active	Substitute is active; ensures long-term availability
RoHS Status	Not specified	ROHS3 Compliant	Substitute provides regulatory compliance
Moisture Sensitivity Level (MSL)	1 (Unlimited)	3 (168 Hours)	Substitute requires controlled storage; standard handling procedures apply

Engineering Selection Recommendations

Product Status Consideration: The IXRFSM18N50 is classified as obsolete. The IXFT50N85XHV is an active product from the same manufacturer (IXYS), ensuring continued availability, technical support, and compliance with current regulatory standards.

Electrical Performance: The IXFT50N85XHV exceeds the electrical specifications of the IXRFSM18N50 across voltage rating (850V vs. 500V), current capacity (50A vs. 19A), and power dissipation (890W vs. 835W). These higher ratings provide design margin and are directly compatible with applications designed for the IXRFSM18N50.

Switching Characteristics: The IXFT50N85XHV exhibits lower on-state resistance (105 mOhm vs. 340 mOhm), resulting in reduced power dissipation and improved thermal performance. However, the substitute has higher gate charge (152 nC vs. 42 nC) and input capacitance (4480 pF vs. 2250 pF). Gate drive circuits must be evaluated to confirm adequate drive capability for the higher capacitive load.

Regulatory Compliance: The IXFT50N85XHV is RoHS3 compliant and REACH unaffected, meeting current environmental and safety standards. The IXRFSM18N50 compliance status is not specified.

Package Consideration: The IXFT50N85XHV uses a TO-268-3 (D³Pak) package, which differs from the IXRFSM18N50's 16-BESOP package. PCB layout modification is required. The TO-268-3 package provides superior thermal performance through a larger exposed pad, which may improve overall system reliability.

Moisture Sensitivity: The IXFT50N85XHV has MSL 3 (168 hours), compared to MSL 1 (unlimited) for the IXRFSM18N50. Standard moisture control procedures during storage and handling are required.

Frequently Asked Questions (FAQ)

Q: Can the IXFT50N85XHV directly replace the IXRFSM18N50 without circuit modification?

A: Electrical substitution is direct for voltage and current requirements. However, gate drive circuit evaluation is necessary due to higher gate charge (152 nC vs. 42 nC) and input capacitance (4480 pF vs. 2250 pF). PCB layout modification is required due to different package types (TO-268-3 vs. 16-BESOP).

Q: What is the impact of the higher gate charge on gate drive design?

A: Higher gate charge increases the energy required to switch the device. Gate drive circuits must supply sufficient current to charge the gate within the required switching time. Verify that the existing gate driver IC has adequate output current capability (typically specified in amperes at the required voltage level).

Q: Are there thermal advantages to using the IXFT50N85XHV?

A: Yes. The IXFT50N85XHV has lower on-state resistance (105 mOhm vs. 340 mOhm), resulting in lower conduction losses. The TO-268-3 package includes a larger exposed pad for improved thermal coupling to the PCB, enhancing heat dissipation compared to the 16-BESOP package.

Q: What is the significance of the different package types?

A: The IXRFSM18N50 uses a 16-BESOP package (0.790", 20.11mm width), while the IXFT50N85XHV uses a TO-268-3 (D³Pak) package. These are mechanically and electrically different. PCB footprint, trace routing, and thermal management design must be updated to accommodate the substitute package.

Q: Does the higher voltage rating (850V vs. 500V) affect circuit operation?

A: No. Higher voltage ratings provide design margin and do not negatively affect circuit operation at lower voltages. The device operates safely at 500V with the 850V-rated substitute.

Q: What is the impact of MSL 3 moisture sensitivity on handling?

A: MSL 3 (168 hours) requires that the device be used within 168 hours of opening the moisture barrier bag. Standard moisture control procedures include storage in dry conditions and use of desiccant packs. This is standard industry practice and does not present a significant constraint for typical manufacturing environments.

Q: Is the IXFT50N85XHV suitable for high-frequency switching applications?

A: The lower gate charge and input capacitance of the IXRFSM18N50 provide faster switching characteristics. The IXFT50N85XHV has higher capacitance values, which may increase switching losses at very high frequencies. Application-specific analysis is required for frequencies above 100 kHz.

Q: Are there any compliance or certification differences between the two parts?

A: The IXFT50N85XHV is RoHS3 compliant and REACH unaffected. The IXRFSM18N50 compliance status is not specified. For applications requiring regulatory compliance, the IXFT50N85XHV is the appropriate choice.

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