FSFR1800USL Equivalent & Substitute Parts

Part Overview

The FSFR1800USL is an offline switching half-bridge power management IC manufactured by onsemi, designed for isolated converter applications with up to 300kHz switching frequency and 260W power handling capability. This component operates with a 500V breakdown voltage and includes integrated fault protection for current limiting, over-temperature, and over-voltage conditions.

The FSFR1800USL is classified as obsolete. Identifying equivalent and substitute parts is necessary to support ongoing system maintenance, design updates, and procurement continuity when original inventory becomes unavailable.

Substiute Parts

FSFR1800USL

onsemiIn Stock: 1836FSFR1800USL Datasheet

Current PartRFQ

FSFR1800XS

onsemiIn Stock: 6489FSFR1800XS Datasheet

SimilarRFQ

FSFR1700XS

Fairchild SemiconductorIn Stock: 1584FSFR1700XS Datasheet

Parametric EquivalentRFQ

FSFR1700XSL

Fairchild SemiconductorIn Stock: 16531FSFR1700XSL Datasheet

Parametric EquivalentRFQ

FSFR1800XSL

Fairchild SemiconductorIn Stock: 2665FSFR1800XSL Datasheet

Parametric EquivalentRFQ

FSFR2100XS

onsemiIn Stock: 32784FSFR2100XS Datasheet

Parametric EquivalentRFQ

FSFR2100XSL

onsemiIn Stock: 1219FSFR2100XSL Datasheet

Parametric EquivalentRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitute parts for the FSFR1800USL are qualified based on the following critical parameters that determine functional compatibility:

Core Electrical Parameters (Must Match):

• Topology: Half-Bridge
• Output Isolation: Isolated
• Voltage - Breakdown: 500V
• Voltage - Supply (Vcc/Vdd): 10V ~ 25V
• Voltage - Start Up: 12.5V
• Duty Cycle: 50%
• Frequency - Switching: Up to 300kHz
• Fault Protection: Current Limiting, Over Temperature, Over Voltage
• Control Features: Frequency Control
• Operating Temperature: -40°C ~ 130°C (TJ)

Mechanical Parameters (Must Match):

• Package / Case: 10-SIP Module, 9 Leads, Formed Leads
• Mounting Type: Through Hole

Allowable Variation:

• Power (Watts): Substitutes with equal or greater power rating are acceptable
• Manufacturer: Different manufacturers permitted if all electrical and mechanical parameters align
• Product Status: Active status substitutes are preferred over obsolete alternatives

Parameter Comparison

Engineering Selection Recommendations

Tier 1 - Preferred Substitutes (Active Status, Full Parameter Match):

FSFR1700XSL is the primary recommended substitute. It maintains all critical electrical parameters identical to the FSFR1800USL, operates at active product status, and provides equivalent 200W power handling with the same 10-SIP package configuration with formed leads. This part offers long-term availability and supply chain stability.

Tier 2 - Compatible Substitutes (Active Status, Minor Variations):

FSFR1700XS is functionally equivalent with active product status. The package designation differs slightly (10-SSIP versus 10-SIP), but both are 9-lead through-hole modules with formed leads. Power rating is 200W, which is lower than the original 260W specification but remains within acceptable substitution parameters for applications not requiring maximum power density.

Tier 3 - Acceptable Substitutes (Obsolete Status, Full Parameter Match):

FSFR1800XS maintains identical electrical specifications and 260W power rating. Despite obsolete status, this part provides direct functional equivalence with the original FSFR1800USL and may be selected when inventory availability permits.

Tier 4 - Higher Power Alternatives (Obsolete Status):

FSFR2100XS and FSFR2100XSL are rated for 400W power handling. These parts are suitable for applications requiring higher power capacity while maintaining all other electrical and mechanical parameters. Both are obsolete status.

Not Recommended:

FSFR1800XSL has incomplete parameter documentation and cannot be fully verified for compatibility despite active product status.

Frequently Asked Questions (FAQ)

Q: Can FSFR1700XSL directly replace FSFR1800USL in my application?

A: Yes. FSFR1700XSL is electrically and mechanically compatible. Both parts share identical topology, isolation, voltage ratings, switching frequency, fault protection, and operating temperature range. The 10-SIP package with formed leads and through-hole mounting are identical. The 200W power rating of FSFR1700XSL is lower than the original 260W, so verify your application does not exceed 200W continuous operation.

Q: What is the difference between FSFR1700XS and FSFR1700XSL?

A: Both parts are electrically identical. The primary difference is package lead formation: FSFR1700XS uses standard 9-SIP leads, while FSFR1700XSL uses L-formed leads. Both are 10-SIP modules with 9 leads and through-hole mounting. Lead formation affects PCB layout and insertion characteristics but not electrical function.

Q: Why is FSFR1800XSL not recommended despite active status?

A: FSFR1800XSL has incomplete technical documentation in available data. Critical parameters including voltage startup, duty cycle, switching frequency, power rating, fault protection, and operating temperature are not specified. This insufficient documentation prevents full compatibility verification.

Q: Can I use FSFR2100XS or FSFR2100XSL as substitutes?

A: Yes, these parts are electrically and mechanically compatible. Both are rated for 400W, providing higher power capacity than the original 260W specification. All other parameters including topology, isolation, voltage ratings, switching frequency, and fault protection are identical. These parts are suitable for applications requiring higher power handling or future design margin.

Q: What does "Formed Leads" mean in the package specification?

A: Formed leads refer to pre-shaped lead geometry optimized for through-hole insertion into PCB sockets or direct soldering. This is distinct from standard straight leads and affects insertion force and PCB layout compatibility. Both FSFR1700XS and FSFR1700XSL use formed leads despite different designations.

Q: Are there compliance or certification differences between substitutes?

A: FSFR1800XS, FSFR2100XS, and FSFR2100XSL carry RoHS3 compliance certification. FSFR1800USL does not specify RoHS status. All parts listed are REACH Unaffected and carry EAR99 ECCN classification. Verify your application's specific compliance requirements before final selection.

Q: What inventory considerations should I account for?

A: FSFR2100XS has the highest current inventory (32,749 pcs), followed by FSFR1700XSL (16,488 pcs). FSFR1800USL has 1,775 pcs available. Inventory levels may affect procurement timeline and cost. Consult with your supplier for current availability and lead times.