Littelfuse 0451007.MRSN Surface Mount Board Mount Fuse Equivalent & Substitute Parts

Part Overview

The Littelfuse 0451007.MRSN is a 7A 125VAC surface mount board mount fuse in the NANO²® 451 series, designed for fast-blow protection in compact 2-SMD applications. This part is active in production and widely used in consumer and industrial electronics requiring reliable overcurrent protection. Substitute parts are identified when equivalent electrical ratings, mechanical dimensions, and approval certifications align with application requirements, enabling design flexibility and supply chain optimization.

Key Parameters

Parameter	Value
Current Rating	7 A
Voltage Rating - AC	125 V
Voltage Rating - DC	Not specified
Response Time	Fast Blow
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 @ Rated Voltage	50A
Melting I²t	10.32
DC Cold Resistance	0.009 Ohms
Operating Temperature Range	-55°C ~ 125°C
Approval Agencies	CSA, METI, UR
RoHS Status	ROHS3 Compliant
Moisture Sensitivity Level	1 (Unlimited)

Substitute Part Grouping Explanation

Substitute parts for the 0451007.MRSN are qualified based on the following critical parameters:

Electrical Equivalence: Current rating of 7A, AC voltage rating of 125V, fast-blow response time, and melting I²t value of 10.32 define the primary protection characteristic.

Mechanical Compatibility: All substitutes maintain identical physical dimensions (0.240" L x 0.106" W x 0.106" H) and 2-SMD square end block package configuration, ensuring PCB footprint compatibility.

Regulatory Compliance: Substitutes must carry active product status and maintain ROHS3 compliance with MSL rating of 1.

Packaging Availability: Substitutes are grouped by packaging format (Tape & Reel or Cut Tape & Digi-Reel®) to support different procurement and assembly workflows.

The following parts meet these criteria: 0448007.MR, 0451007.MRL, 0451007.NRL, 0453007.MR, and 0476007.MR.

Parameter Comparison

Part Number	Series	Current (A)	Voltage AC (V)	Voltage DC (V)	Melting I²t	Breaking Capacity	DC Resistance (Ω)	Packaging	Inventory (Pcs)
0451007.MRSN	NANO²® 451	7	125	Not specified	10.32	50A	0.009	Tape & Reel (TR)	1937
0448007.MR	NANO²® 448	7	125	125	13.92	50A	0.009	Tape & Reel (TR)	17043
0451007.MRL	NANO²® 451	7	125	125	10.32	50A	0.009	Cut Tape (CT) & Digi-Reel®	40200
0451007.NRL	NANO²® 451	7	125	125	10.32	50A	0.009	Tape & Reel (TR)	5007
0453007.MR	NANO²® 453	7	125	125	10.32	50A	0.009	Cut Tape (CT) & Digi-Reel®	15723
0476007.MR	NANO²®476	7	125	125	7.8	100A AC, 300A DC	0.0116	Tape & Reel (TR)	2456

Engineering Selection Recommendations

Primary Substitutes (Highest Compatibility): Parts 0451007.MRL, 0451007.NRL, and 0453007.MR maintain identical electrical characteristics (7A, 125V AC/DC, 10.32 I²t) and mechanical dimensions. These are direct functional equivalents with active product status and full ROHS3 compliance. Selection between these depends on packaging preference: Tape & Reel for 0451007.NRL or Cut Tape & Digi-Reel® for 0451007.MRL and 0453007.MR.

Secondary Substitute (Electrical Variation): Part 0448007.MR carries a higher melting I²t value of 13.92 compared to the reference 10.32, indicating a slower thermal response. This part is suitable only when the application circuit design accommodates the extended response time. It offers the advantage of higher inventory availability (17043 units).

Alternative Substitute (Enhanced Breaking Capacity): Part 0476007.MR features significantly higher breaking capacity (100A AC, 300A DC versus 50A) and lower melting I²t (7.8), indicating faster response. This part is suitable for applications requiring enhanced fault protection but carries REACH Affected status and should be evaluated for regulatory compliance in the target market.

Inventory Considerations: Part 0451007.MRL offers the highest stock level (40200 units), supporting high-volume production schedules. Parts 0451007.NRL and 0476007.MR have lower availability and should be confirmed with supplier before design commitment.

Frequently Asked Questions (FAQ)

Q: Can 0451007.MRL be used as a direct replacement for 0451007.MRSN?

A: Yes. Both parts are from the NANO²® 451 series with identical current rating (7A), voltage rating (125V AC/DC), melting I²t (10.32), and physical dimensions. The difference is packaging format: 0451007.MRSN uses Tape & Reel, while 0451007.MRL uses Cut Tape & Digi-Reel®. PCB footprint and electrical performance are identical.

Q: What is the significance of the melting I²t parameter in selecting a substitute?

A: Melting I²t determines the thermal response speed of the fuse. The reference part 0451007.MRSN has an I²t of 10.32. Substitutes with the same I²t (0451007.MRL, 0451007.NRL, 0453007.MR) provide identical protection timing. Part 0448007.MR with I²t of 13.92 responds more slowly; part 0476007.MR with I²t of 7.8 responds faster. Selection must align with circuit protection requirements.

Q: Are all substitute parts ROHS3 compliant?

A: Yes, all listed substitutes carry ROHS3 compliance. However, part 0476007.MR is marked as REACH Affected, while others are REACH Unaffected. Verify REACH compliance requirements for your target market before final selection.

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

A: Tape & Reel packaging is continuous and suitable for high-speed automated assembly. Cut Tape & Digi-Reel® provides flexibility for lower-volume production or mixed-component assembly. Both formats contain identical components; the choice depends on assembly equipment and production volume.

Q: Can 0476007.MR be used in place of 0451007.MRSN?

A: Electrical substitution is possible due to matching current and voltage ratings. However, the breaking capacity is significantly higher (100A AC, 300A DC versus 50A), and the melting I²t is lower (7.8 versus 10.32), resulting in faster response. Use only if the circuit design accommodates faster fault detection and the higher breaking capacity does not create unintended nuisance trips. Verify REACH compliance for your application region.

Q: Which substitute offers the best inventory availability?

A: Part 0451007.MRL from the NANO²® 451 series offers the highest stock level at 40200 units, with identical electrical and mechanical specifications to the reference part. This is the recommended choice for high-volume production requiring immediate availability.

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