4N37FR2M Equivalent & Substitute Parts

Part Overview

The 4N37FR2M is an optoisolator transistor with base output manufactured by onsemi, designed for high-voltage isolation applications. This component features a 7500Vpk isolation rating and is packaged in a 6-SMD surface mount configuration. The part is currently listed as obsolete, making identification of suitable substitute components essential for ongoing design support and production continuity. Equivalent parts must maintain functional compatibility across isolation voltage, switching characteristics, and output specifications.

Substiute Parts

4N37FR2M

onsemiIn Stock: 8314N37FR2M Datasheet

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4N37SR2M

onsemiIn Stock: 18614N37SR2M Datasheet

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4N37

Vishay Semiconductor Opto DivisionIn Stock: 190924N37 Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution of the 4N37FR2M is determined by the following critical parameters:

• Isolation Voltage: The 4N37FR2M provides 7500Vpk isolation. Substitute parts must meet or exceed this isolation rating to maintain electrical safety and regulatory compliance in high-voltage isolation applications.
• Output Configuration: The transistor with base output is essential for applications requiring base drive control. Substitute parts must provide identical output topology.
• Current Transfer Ratio: Minimum 100% @ 10mA ensures consistent optical coupling efficiency across the specified input current range.
• Switching Speed: Turn-on and turn-off times of 2µs define the maximum switching frequency capability. Substitute parts with equivalent or faster switching characteristics maintain system performance.
• Mounting Type and Package: Surface mount 6-SMD packaging is required for PCB compatibility. Package footprint and lead configuration must match the original design.
• Operating Temperature Range: The -55°C to 100°C range defines the thermal operating envelope. Substitute parts must support this full range or a compatible subset.

Parameter Comparison

Engineering Selection Recommendations

4N37SR2M (onsemi, Surface Mount)

The 4N37SR2M is the closest functional equivalent to the 4N37FR2M. Both components share identical packaging (6-SMD, Gull Wing), mounting type (surface mount), switching characteristics (2µs turn-on/off times), and output specifications (30V max, 300mV Vce saturation). The primary difference is isolation voltage: 4N37SR2M provides 4170Vrms compared to 4N37FR2M's 7500Vpk. This part is currently active with ROHS3 compliance and represents the direct onsemi surface mount replacement. Selection of this part is appropriate only for applications where the lower isolation voltage is acceptable.

4N37 (Vishay, Through Hole)

The Vishay 4N37 maintains the same base product number and core functionality but differs in mounting technology (through-hole 6-DIP versus surface mount 6-SMD). This part provides 5000Vrms isolation, intermediate between the main part and the 4N37SR2M. Switching speed is slower (10µs versus 2µs), and maximum forward current is reduced to 50mA. This part is active and ROHS3 compliant but requires PCB redesign to accommodate through-hole mounting. Selection is appropriate only when through-hole mounting is required and slower switching speed is acceptable.

Frequently Asked Questions (FAQ)

Q: Can the 4N37SR2M directly replace the 4N37FR2M in existing designs?

A: Direct replacement is possible only if the application isolation voltage requirement does not exceed 4170Vrms. The 4N37SR2M provides lower isolation voltage (4170Vrms versus 7500Vpk) but maintains identical packaging, switching speed, and output characteristics. Verify isolation voltage requirements before substitution.

Q: What is the primary limitation of the Vishay 4N37 as a substitute?

A: The Vishay 4N37 uses through-hole 6-DIP packaging instead of surface mount 6-SMD. This requires PCB redesign and cannot be used as a direct footprint replacement. Additionally, switching speed is reduced to 10µs compared to 2µs for the main part, which may impact system performance in high-frequency applications.

Q: Are there isolation voltage differences between the main part and substitutes?

A: Yes. The 4N37FR2M provides 7500Vpk isolation. The 4N37SR2M provides 4170Vrms (approximately 5900Vpk equivalent), and the Vishay 4N37 provides 5000Vrms (approximately 7070Vpk equivalent). Applications requiring the full 7500Vpk isolation rating cannot use the 4N37SR2M. The Vishay part approaches but does not fully meet the original specification.

Q: What compliance certifications apply to substitute parts?

A: The 4N37SR2M and Vishay 4N37 are both ROHS3 compliant. All three parts (main and substitutes) are REACH unaffected and carry EAR99 ECCN classification. Moisture sensitivity level is 1 (unlimited) for all variants.

Q: Can the 4N37FR2M be used in new designs given its obsolete status?

A: The 4N37FR2M is listed as obsolete. New designs should specify either the 4N37SR2M (if isolation voltage can be reduced to 4170Vrms and surface mount is required) or the Vishay 4N37 (if through-hole mounting is acceptable and isolation voltage of 5000Vrms is sufficient). Existing inventory of the main part may support legacy production, but long-term availability cannot be assured.