FSL337LRN Equivalent & Substitute Parts

Part Overview

The FSL337LRN is an offline switch IC manufactured by onsemi, designed for power management applications supporting Buck, Buck-Boost, and Flyback topologies. This component is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement. The FSL337LRN operates at 50kHz switching frequency with 20W power capability and includes integrated fault protection features including current limiting, overload, overvoltage, and overtemperature protection.

Substiute Parts

FSL337LRN

onsemiIn Stock: 758FSL337LRN Datasheet

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FSL538APG

onsemiIn Stock: 1019FSL538APG Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution of the FSL337LRN is determined by the following critical parameters:

• Package Compatibility: Both main and substitute parts must use 8-DIP (0.300", 7.62mm) through-hole packaging to ensure PCB layout compatibility
• Topology Support: The substitute must support at least one of the topologies required by the application (Buck, Buck-Boost, or Flyback)
• Voltage Ratings: Breakdown voltage and startup voltage must meet or exceed application requirements
• Switching Frequency: Operating frequency affects transformer design and EMI characteristics
• Power Rating: Substitute must support the required power level
• Fault Protection: Essential protection features must be present
• Control Interface: Enable and soft start features must be available
• Temperature Range: Operating temperature must cover the application environment
• Compliance: RoHS3 compliance required for regulatory alignment

The FSL538APG qualifies as a substitute based on matching package format, through-hole mounting, compatible topology (Flyback), higher voltage ratings, equivalent control features, and identical compliance certifications.

Parameter Comparison

Engineering Selection Recommendations

Both the FSL337LRN and FSL538APG are obsolete products from onsemi, requiring substitution for new designs or ongoing procurement. Selection between these parts depends on application-specific topology requirements:

FSL337LRN supports multiple topologies (Buck, Buck-Boost, Flyback) with lower startup voltage (8V) and lower switching frequency (50kHz), suitable for applications requiring topology flexibility and lower frequency operation.

FSL538APG is optimized for Flyback topology exclusively, with higher voltage ratings (800V breakdown), higher switching frequency (100kHz), and higher power capability (25W). The higher startup voltage (16V) requires consideration in low-input-voltage applications.

Both parts maintain identical operating temperature range (-40°C to 125°C), RoHS3 compliance, and equivalent control features (EN, Soft Start). PCB layout compatibility is ensured through identical 8-DIP through-hole packaging.

Frequently Asked Questions (FAQ)

Q: Can FSL538APG directly replace FSL337LRN in all applications?

A: Direct replacement is possible only in Flyback topology applications. Applications using Buck or Buck-Boost topologies require circuit redesign, as FSL538APG supports Flyback topology exclusively.

Q: What are the key differences in electrical performance?

A: FSL538APG offers higher voltage breakdown (800V vs 700V), higher switching frequency (100kHz vs 50kHz), and higher power rating (25W vs 20W). The startup voltage is higher (16V vs 8V), which may affect low-input-voltage circuit operation.

Q: Are both parts pin-compatible?

A: Both parts use 8-DIP (0.300", 7.62mm) through-hole packaging with 7 leads. Physical package compatibility is confirmed. However, functional pin assignments must be verified against respective datasheets before PCB implementation.

Q: What compliance certifications apply to both parts?

A: Both FSL337LRN and FSL538APG are RoHS3 compliant, REACH unaffected, and classified under ECCN EAR99 with HTSUS code 8542.39.0001.

Q: Are there inventory considerations for these obsolete parts?

A: FSL337LRN has 651 pieces available as new original stock. FSL538APG has 977 pieces available as new original stock. Both are classified as obsolete products.