FSQ321 Equivalent & Substitute Parts

Part Overview

The FSQ321 is an offline switch flyback converter IC manufactured by onsemi, designed for isolated power management applications. Operating at 55kHz to 67kHz switching frequency with 12W power output capability, this component integrates an internal switch with comprehensive fault protection including current limiting, overload, over-temperature, and over-voltage protection. The FSQ321 is classified as obsolete, making identification of suitable substitute components essential for ongoing design support and production continuity.

Substiute Parts

FSQ321

onsemiIn Stock: 4496FSQ321 Datasheet

Current PartRFQ

FSQ0365RN

onsemiIn Stock: 5980FSQ0365RN Datasheet

Parametric EquivalentRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the FSQ321 is determined by strict equivalence across the following critical parameters:

• Topology & Isolation: Flyback converter with isolated output
• Voltage Rating: 650V breakdown voltage, 8V–20V supply range, 12V startup voltage
• Switching Frequency: 55kHz–67kHz operating band
• Package & Mounting: 8-DIP through-hole form factor (0.300", 7.62mm)
• Fault Protection: Current limiting, overload, over-temperature, and over-voltage protection
• Control Architecture: Synchronous control features
• Operating Temperature Range: -40°C to 85°C

The FSQ0365RN meets all these core parameters while maintaining identical electrical and mechanical compatibility. The primary distinction is increased power rating (25W versus 12W) and active product status, making it a direct functional substitute.

Parameter Comparison

Engineering Selection Recommendations

The FSQ0365RN is the direct parametric equivalent for FSQ321 replacement. Both components share identical electrical specifications across voltage ratings, switching frequency, protection features, and operating temperature range. The FSQ0365RN maintains full ROHS3 compliance and REACH unaffected status, meeting regulatory requirements equivalent to the original part.

The FSQ0365RN's active product status ensures ongoing availability and manufacturing support, eliminating supply chain risk associated with the obsolete FSQ321. The increased power rating (25W) provides design margin without compromising compatibility, as the component operates within the same electrical envelope and package footprint.

Pin-for-pin compatibility and identical package specifications (8-DIP through-hole) enable direct board-level substitution without layout modifications.

Frequently Asked Questions (FAQ)

Q: Can FSQ0365RN directly replace FSQ321 in existing designs?

A: Yes. Both components are pin-for-pin compatible with identical 8-DIP through-hole packaging. Electrical parameters including voltage ratings, switching frequency, and fault protection are equivalent. No circuit modifications are required.

Q: What is the primary difference between FSQ321 and FSQ0365RN?

A: The FSQ0365RN has a higher power rating (25W versus 12W) and active product status. All other electrical and mechanical specifications are identical.

Q: Are there compliance or certification differences?

A: Both parts are ROHS3 compliant and REACH unaffected. Regulatory status is equivalent.

Q: Does the higher power rating of FSQ0365RN affect circuit operation?

A: No. The higher power rating indicates increased capability without changing the component's electrical interface or operating characteristics within the specified voltage and frequency ranges.

Q: What packaging options are available for FSQ0365RN?

A: FSQ0365RN is supplied in tube packaging. The 8-DIP form factor and through-hole mounting type remain consistent with FSQ321 specifications.