Littelfuse 04511.25MRSN Surface Mount Board Fuse Equivalent & Substitute Parts

Part Overview

The Littelfuse 04511.25MRSN is a 1.25 A, 125 V AC surface mount board fuse in the NANO²® 451 series. This fast-blow fuse is designed for board-level protection in electronic equipment requiring compact, high-reliability overcurrent protection. The part is actively manufactured and stocked, with 926 units available in Tape & Reel packaging. Equivalent and substitute parts are identified for applications requiring alternative packaging formats, series variants, or enhanced DC voltage ratings while maintaining identical electrical performance characteristics.

Substiute Parts

04511.25MRSN

Littelfuse Inc.In Stock: 98404511.25MRSN Datasheet

Current PartRFQ

04481.25MR

Littelfuse Inc.In Stock: 210904481.25MR Datasheet

Parametric EquivalentRFQ

04511.25MRL

Littelfuse Inc.In Stock: 643704511.25MRL Datasheet

Parametric EquivalentRFQ

04531.25MR

Littelfuse Inc.In Stock: 534004531.25MR Datasheet

Parametric EquivalentRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitute parts for the 04511.25MRSN are qualified based on the following electrical and mechanical parameters:

Mandatory Matching Parameters:

• Current Rating: 1.25 A
• Voltage Rating (AC): 125 V
• Response Time: Fast Blow
• Mounting Type: Surface Mount
• Package / Case: 2-SMD, Square End Block
• Physical Dimensions: 0.240" L x 0.106" W x 0.106" H (6.10mm x 2.69mm x 2.69mm)
• Breaking Capacity: 50 A @ Rated Voltage
• Operating Temperature Range: -55°C to 125°C
• RoHS Status: ROHS3 Compliant
• Moisture Sensitivity Level: 1 (Unlimited)

Variable Parameters Allowing Substitution:

• Series designation (NANO²® 451, 448, 453)
• Packaging format (Tape & Reel vs. Cut Tape & Digi-Reel®)
• DC voltage rating (when specified in substitute)
• Melting I²t characteristics (within acceptable tolerance)
• DC cold resistance values
• Approval agency certifications (CSA, UL, PSE combinations)

All identified substitutes maintain electrical equivalence for 1.25 A, 125 V AC fast-blow fuse applications while offering flexibility in packaging and series selection.

Parameter Comparison

Engineering Selection Recommendations

All four parts maintain active product status and ROHS3 compliance, ensuring long-term availability and environmental regulatory adherence. Selection among these equivalents should be based on specific application requirements:

04511.25MRSN (Primary Part): Suitable for applications requiring CSA and UR certifications with Tape & Reel packaging. Appropriate for standard AC-only protection circuits.

04481.25MR (NANO²® 448 Series): Provides enhanced DC voltage rating (125 V DC) and broader approval agency coverage (CSA, UL, PSE). Melting I²t of 0.9 indicates slightly slower thermal response compared to the primary part. Recommended for dual AC/DC rated applications requiring UL certification.

04511.25MRL (NANO²® 451 Series, Cut Tape Format): Electrically identical to the primary part with DC voltage rating (125 V DC) and expanded certifications (CSA, PSE, UL). Cut Tape & Digi-Reel® packaging offers flexibility for lower-volume or mixed-component procurement. Highest inventory availability (6400 units) supports extended production runs.

04531.25MR (NANO²® 453 Series): Provides DC voltage rating (125 V DC) and comprehensive certifications (CSA, PSE, UL). Electrically equivalent to the primary part with identical melting I²t and DC cold resistance. Tape & Reel packaging maintains standard assembly compatibility.

Frequently Asked Questions (FAQ)

Q: Can the 04481.25MR substitute for the 04511.25MRSN in all applications?

A: The 04481.25MR is electrically equivalent for 1.25 A, 125 V AC fast-blow protection. However, the melting I²t value differs (0.9 vs. 0.664), indicating a slightly different thermal response curve. Substitution is valid for applications where this thermal characteristic variance is acceptable. The 04481.25MR adds DC voltage rating (125 V) and UL certification, making it suitable for dual AC/DC circuits.

Q: What is the difference between Tape & Reel and Cut Tape & Digi-Reel® packaging?

A: Tape & Reel (TR) packaging provides continuous component reels suitable for high-volume automated assembly. Cut Tape (CT) & Digi-Reel® packaging offers flexibility for lower-volume orders or mixed-component kits. Both formats are compatible with standard surface mount assembly equipment. The 04511.25MRL in Cut Tape format maintains identical electrical specifications and is interchangeable at the circuit level.

Q: Are all substitute parts certified to the same standards?

A: The primary part (04511.25MRSN) carries CSA and UR certifications. Substitute parts carry expanded certifications: 04481.25MR includes CSA, UL, and PSE; 04511.25MRL includes CSA, PSE, and UL; 04531.25MR includes CSA, PSE, and UL. Applications requiring specific certification standards should reference the approval agency list for each part.

Q: Can I use the 04481.25MR if my circuit requires only AC voltage protection?

A: Yes. The 04481.25MR is rated for 125 V AC and 125 V DC. The DC rating does not restrict AC-only applications; it indicates the part is qualified for both AC and DC circuits. The electrical performance for 125 V AC protection is identical to the primary part.

Q: Which substitute offers the best inventory availability?

A: The 04511.25MRL (NANO²® 451 series, Cut Tape & Digi-Reel® format) has the highest inventory availability at 6400 units. This part is electrically identical to the primary part and adds DC voltage rating and expanded certifications, making it suitable for extended production requirements.

Q: What does Melting I²t indicate, and why does it differ among these parts?

A: Melting I²t is a thermal characteristic that defines the fuse's response to overcurrent conditions. The primary part and 04511.25MRL share a melting I²t of 0.664, while the 04481.25MR has 0.9. Lower values indicate faster thermal response. For 1.25 A fast-blow applications, both values are within the fast-blow classification. Selection should align with circuit protection requirements and thermal response expectations.

Q: Are these parts suitable for high-temperature applications?

A: All parts are rated for operating temperatures from -55°C to 125°C. This range supports industrial and consumer electronics applications across standard environmental conditions. Thermal derating may apply in extreme ambient conditions; refer to detailed thermal performance curves for specific high-temperature applications.