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

Part Overview

The Littelfuse 0451007.MR is a 7A 125VAC/125VDC surface mount board mount fuse in the NANO²® 451 series, featuring a 2-SMD square end block package. This part is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement. The fuse provides fast-blow response with a 50A breaking capacity at rated voltage and operates across -55°C to 125°C. Direct replacements and parametric equivalents are available from both Littelfuse and alternative manufacturers to ensure design continuity.

Key Parameters

Parameter	Value
Current Rating	7 A
Voltage Rating (AC)	125 V
Voltage Rating (DC)	125 V
Response Time	Fast Blow
Mounting Type	Surface Mount
Fuse Type	Board Mount (Cartridge Style Excluded)
Package / Case	2-SMD, Square End Block
Size / Dimension	0.240" L x 0.106" W x 0.106" H (6.10mm x 2.69mm x 2.69mm)
Operating Temperature Range	-55°C ~ 125°C
Breaking Capacity @ Rated Voltage	50A
DC Cold Resistance	0.009 Ohms
Approval Agency	CSA, PSE, UL

Substitute Part Grouping Explanation

Substitution for the 0451007.MR is determined by strict equivalence across the following critical parameters: current rating (7A), AC voltage rating (125V), DC voltage rating (125V), response time (fast blow), mounting type (surface mount), package configuration (2-SMD square end block), and physical dimensions (0.240" x 0.106" x 0.106").

Substitute parts are grouped into three categories:

Direct Manufacturer Equivalents (Littelfuse): Parts 0451007.MRL and 0451007.NRL maintain identical electrical and mechanical specifications to the main part, differing only in packaging format (Cut Tape & Digi-Reel® or Tape & Reel). These are direct functional replacements with no performance variation.

Parametric Equivalents (Littelfuse Series): Parts 0448007.MR, 0453007.MR, 0453007.NR, 0476007.MR, and 0476007.MRSN share the same current, voltage, response time, mounting, and package specifications. Variations exist in melting I²t, breaking capacity, DC cold resistance, and approval agencies, which do not affect functional interchangeability for standard circuit protection applications.

Cross-Manufacturer Equivalents (Bourns): Parts SF-2410FP700T-2 and SF-2410HI700T-2 from Bourns Inc. meet all critical electrical and mechanical parameters. Minor dimensional variations (0.102" width and height versus 0.106") and differences in melting I²t and DC cold resistance are within acceptable tolerance for board mount fuse applications.

Parameter Comparison

Part Number	Manufacturer	Series	Current (A)	Voltage AC (V)	Voltage DC (V)	Response Time	Breaking Capacity	Melting I²t	DC Cold Resistance (Ω)	Product Status	RoHS Status	Packaging
0451007.MR	Littelfuse Inc.	NANO²® 451	7	125	125	Fast Blow	50A	10.32	0.009	Obsolete	RoHS non-compliant	-
0451007.MRL	Littelfuse Inc.	NANO²® 451	7	125	125	Fast Blow	50A	10.32	0.009	Active	ROHS3 Compliant	Cut Tape (CT) & Digi-Reel®
0451007.NRL	Littelfuse Inc.	NANO²® 451	7	125	125	Fast Blow	50A	10.32	0.009	Active	ROHS3 Compliant	Tape & Reel (TR)
0448007.MR	Littelfuse Inc.	NANO²® 448	7	125	125	Fast Blow	50A	13.92	0.009	Active	ROHS3 Compliant	Tape & Reel (TR)
0453007.MR	Littelfuse Inc.	NANO²® 453	7	125	125	Fast Blow	50A	10.32	0.009	Active	ROHS3 Compliant	Cut Tape (CT) & Digi-Reel®
0453007.NR	Littelfuse Inc.	NANO²® 453	7	125	125	Fast Blow	50A	10.32	0.009	Active	ROHS3 Compliant	Tape & Reel (TR)
0476007.MR	Littelfuse Inc.	NANO²®476	7	125	125	Fast Blow	100A AC, 300A DC	7.8	0.0116	Active	ROHS3 Compliant	Tape & Reel (TR)
0476007.MRSN	Littelfuse Inc.	NANO²®476	7	125	125	Fast Blow	100A AC, 300A DC	7.8	0.0116	Active	ROHS3 Compliant	Tape & Reel (TR)
SF-2410FP700T-2	Bourns Inc.	SinglFuse™ SF-2410FP-T	7	125	125	Fast Blow	50A	9.016	0.01	Active	ROHS3 Compliant	Tape & Reel (TR)
SF-2410HI700T-2	Bourns Inc.	SinglFuse™ SF-2410HI-T	7	125	125	Fast Blow	50A	100.06	0.0083	Active	ROHS3 Compliant	Tape & Reel (TR)

Engineering Selection Recommendations

Primary Recommendation: 0451007.MRL is the preferred direct replacement. It maintains identical electrical and thermal characteristics to the obsolete 0451007.MR while offering active product status and ROHS3 compliance. Packaging in Cut Tape & Digi-Reel® format supports both manual and automated assembly workflows.

Alternative from Littelfuse: 0451007.NRL provides equivalent performance with Tape & Reel packaging, suitable for high-volume automated assembly. Both 0451007.MRL and 0451007.NRL are recommended for designs requiring strict parameter matching to the original part.

Parametric Equivalents: Parts 0448007.MR, 0453007.MR, 0453007.NR, 0476007.MR, and 0476007.MRSN are functionally interchangeable. The 0476007 series offers enhanced breaking capacity (100A AC, 300A DC) compared to the standard 50A rating, providing additional margin in high-fault-current environments. All Littelfuse alternatives carry active product status and ROHS3 compliance.

Cross-Manufacturer Option: Bourns SF-2410FP700T-2 and SF-2410HI700T-2 are electrically equivalent with minor dimensional variations. Both carry active status and ROHS3 compliance. The SF-2410HI700T-2 exhibits significantly higher melting I²t (100.06 versus 10.32), affecting response characteristics; selection depends on circuit protection requirements.

Frequently Asked Questions (FAQ)

Q: Can I use 0451007.MRL as a direct replacement for the obsolete 0451007.MR?

A: Yes. The 0451007.MRL is a direct functional equivalent with identical current rating (7A), voltage ratings (125VAC/125VDC), response time (fast blow), and physical dimensions. The primary difference is packaging format and RoHS compliance status. No circuit redesign is required.

Q: What is the difference between 0451007.MRL and 0451007.NRL?

A: Both parts are electrically and mechanically identical. The difference is packaging: 0451007.MRL uses Cut Tape & Digi-Reel® format, while 0451007.NRL uses Tape & Reel format. Selection depends on assembly equipment compatibility and procurement volume requirements.

Q: Why do the 0476007 series parts have higher breaking capacity?

A: The 0476007.MR and 0476007.MRSN are rated for 100A AC and 300A DC breaking capacity compared to 50A for the standard series. This provides enhanced protection in circuits with higher fault current potential. All other electrical parameters remain equivalent to the 0451007.MR.

Q: Are Bourns SF-2410 series fuses compatible with Littelfuse NANO²® designs?

A: Yes, the SF-2410FP700T-2 and SF-2410HI700T-2 meet the same current, voltage, response time, and mounting specifications. Minor dimensional variations (0.102" versus 0.106" width and height) are within acceptable tolerance for board mount applications. Verify PCB footprint compatibility before implementation.

Q: What is the significance of melting I²t differences between substitute parts?

A: Melting I²t indicates the thermal energy required to melt the fuse element. Lower values (7.8 for 0476007 series) indicate faster response to overcurrent, while higher values (100.06 for SF-2410HI700T-2) indicate slower response. Selection depends on circuit protection requirements and tolerance for transient current spikes.

Q: Are all substitute parts RoHS compliant?

A: The original 0451007.MR is RoHS non-compliant. All recommended substitutes (0451007.MRL, 0451007.NRL, Littelfuse parametric equivalents, and Bourns alternatives) are ROHS3 compliant, meeting current environmental regulations.

Q: Can I mix packaging formats in the same production run?

A: Packaging format (Cut Tape & Digi-Reel® versus Tape & Reel) affects assembly line compatibility and handling. Verify your assembly equipment specifications before mixing formats. Electrical performance is identical across all packaging options.

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