Littelfuse 0451005.NRL Surface Mount Board Mount Fuse Equivalent & Substitute Parts

Part Overview

The Littelfuse 0451005.NRL is a 5 A, 125 V AC/DC surface mount board mount fuse in the NANO²® 451 series. This fast-blow fuse is designed for circuit protection in applications requiring compact 2-SMD, square end block packaging. The part is active in production with CSA, PSE, and UR approvals. Equivalent and substitute parts are identified for applications requiring alternative packaging formats, different series variants, or sourcing from alternative manufacturers while maintaining electrical and mechanical compatibility.

Key Parameters

Parameter	Value
Current Rating	5 A
Voltage Rating (AC)	125 V
Voltage Rating (DC)	125 V
Response Time	Fast Blow
Mounting Type	Surface Mount
Package / Case	2-SMD, Square End Block
Breaking Capacity @ Rated Voltage	50 A
Operating Temperature Range	-55°C ~ 125°C
Size / Dimension	0.240" L x 0.106" W x 0.106" H (6.10mm x 2.69mm x 2.69mm)
RoHS Status	ROHS3 Compliant
Moisture Sensitivity Level (MSL)	1 (Unlimited)

Substitute Part Grouping Explanation

Substitute parts are grouped into three categories based on substitution criteria:

Parametric Equivalents (Littelfuse NANO²® Series): Parts 0448005.MR, 0451005.MRL, 0451005.MRSN, and 0453005.MR share identical electrical ratings (5 A, 125 V AC/DC), response time (fast blow), mounting type (surface mount), and package format (2-SMD, square end block). These parts differ in series designation, packaging format (tape & reel versus cut tape), and approval agency certifications. Parametric equivalents are suitable for direct substitution where series compatibility and packaging format are not design constraints.

Direct Manufacturer Equivalents (Bourns SinglFuse™ Series): Parts SF-2410FP500T-2 and SF-2410HI500T-2 are manufactured by Bourns Inc. and meet identical electrical specifications (5 A, 125 V AC/DC, fast blow, 50 A breaking capacity). These parts use the same 2-SMD, square end block package format and surface mount configuration. Direct manufacturer equivalents are suitable for applications where cross-manufacturer sourcing is acceptable.

Key Parameters for Substitution Compatibility:

Current Rating: 5 A (all substitutes)
Voltage Rating: 125 V AC / 125 V DC (all substitutes)
Response Time: Fast Blow (all substitutes)
Mounting Type: Surface Mount (all substitutes)
Package / Case: 2-SMD, Square End Block (all substitutes)
Breaking Capacity: 50 A (all substitutes)
Operating Temperature: -55°C ~ 125°C (all substitutes)

Parameter Comparison

Part Number	Manufacturer	Series	Current Rating (A)	Voltage AC (V)	Voltage DC (V)	Response Time	Breaking Capacity (A)	Melting I²t	DC Cold Resistance (Ohms)	Packaging	Inventory (Pcs)
0451005.NRL	Littelfuse Inc.	NANO²® 451	5	125	125	Fast Blow	50	5.566	0.0125	Tape & Reel (TR)	3,427
0448005.MR	Littelfuse Inc.	NANO²® 448	5	125	125	Fast Blow	50	4.49	0.01531	Tape & Reel (TR)	40,634
0451005.MRL	Littelfuse Inc.	NANO²® 451	5	125	125	Fast Blow	50	5.566	0.0125	Cut Tape (CT) & Digi-Reel®	105,034
0451005.MRSN	Littelfuse Inc.	NANO²® 451	5	125	125	Fast Blow	50	5.566	0.0125	Tape & Reel (TR)	2,922
0453005.MR	Littelfuse Inc.	NANO²® 453	5	125	125	Fast Blow	50	5.566	0.0125	Tape & Reel (TR)	25,998
SF-2410FP500T-2	Bourns Inc.	SinglFuse™ SF-2410FP-T	5	125	125	Fast Blow	50	6.175	0.013	Tape & Reel (TR)	6,799
SF-2410HI500T-2	Bourns Inc.	SinglFuse™ SF-2410HI-T	5	125	125	Fast Blow	50	50.308	0.0112	Tape & Reel (TR)	5,739

Engineering Selection Recommendations

Littelfuse NANO²® Series Substitutes (0448005.MR, 0451005.MRL, 0451005.MRSN, 0453005.MR): These parts maintain full electrical and mechanical compatibility with the primary part 0451005.NRL. Selection among these options depends on packaging format requirements and approval agency certifications. Part 0451005.MRL offers the highest inventory availability (105,034 pcs) and is available in cut tape and Digi-Reel® format, suitable for applications with flexible packaging requirements. Part 0448005.MR provides high inventory (40,634 pcs) with CSA, UL, and PSE approvals. Part 0451005.MRSN includes METI approval for Japanese market applications. Part 0453005.MR is suitable for applications where REACH compliance is required.

Bourns SinglFuse™ Series Substitutes (SF-2410FP500T-2, SF-2410HI500T-2): These cross-manufacturer alternatives meet all electrical specifications and are suitable for applications where multi-source qualification is required. Both parts carry cUL and UL approvals. The SF-2410FP500T-2 variant provides standard fast-blow characteristics with melting I²t of 6.175. The SF-2410HI500T-2 variant exhibits higher melting I²t (50.308), indicating slower thermal response characteristics within the fast-blow category, and is suitable for applications requiring enhanced surge tolerance.

Approval Agency Considerations: The primary part 0451005.NRL carries CSA, PSE, and UR approvals. Littelfuse parametric equivalents offer varying approval combinations (CSA/UL/PSE, CSA/METI/UR, CSA/PSE/UL). Bourns direct equivalents carry cUL and UL approvals. Selection should align with regional regulatory requirements and end-application certification standards.

Frequently Asked Questions (FAQ)

Q: Can 0451005.NRL be directly replaced with 0451005.MRL? A: Yes. Both parts are from the NANO²® 451 series with identical electrical ratings (5 A, 125 V AC/DC), response time (fast blow), and package format (2-SMD, square end block). The primary difference is packaging format: 0451005.NRL uses tape & reel, while 0451005.MRL uses cut tape and Digi-Reel®. Direct substitution is suitable where packaging format compatibility exists.

Q: What is the difference between Littelfuse and Bourns fuse substitutes? A: Littelfuse parametric equivalents (0448005.MR, 0451005.MRL, 0451005.MRSN, 0453005.MR) are from the same manufacturer and NANO²® series family, differing primarily in series designation and approval certifications. Bourns direct equivalents (SF-2410FP500T-2, SF-2410HI500T-2) are from a different manufacturer but meet identical electrical specifications. Cross-manufacturer substitution requires design qualification and approval agency verification.

Q: Are there dimensional differences between substitute parts? A: Littelfuse NANO²® series parts maintain consistent dimensions (0.240" L x 0.106" W x 0.106" H / 6.10mm x 2.69mm x 2.69mm). Bourns SinglFuse™ parts have slightly different width and height dimensions (0.240" L x 0.102" W x 0.102" H / 6.10mm x 2.59mm x 2.59mm). These dimensional variations remain within the 2-SMD, square end block package category and are suitable for standard PCB footprints designed for this package type.

Q: Which substitute part offers the best inventory availability? A: Part 0451005.MRL (Littelfuse NANO²® 451, cut tape & Digi-Reel®) provides the highest inventory availability at 105,034 pcs. This part is electrically identical to the primary part 0451005.NRL and is suitable for high-volume applications.

Q: What approval agencies are represented across all substitute options? A: Littelfuse substitutes carry CSA, PSE, UL, METI, and UR approvals across the product line. Bourns substitutes carry cUL and UL approvals. Applications requiring specific regional certifications (CSA for North America, PSE for Japan, METI for Japanese market, UR for Russia) should select parts with corresponding approval designations.

Q: Can SF-2410HI500T-2 be used in place of SF-2410FP500T-2? A: Both parts meet the same electrical ratings and package specifications. The primary difference is melting I²t: SF-2410FP500T-2 has melting I²t of 6.175, while SF-2410HI500T-2 has melting I²t of 50.308. The higher I²t value in SF-2410HI500T-2 indicates slower thermal response. Substitution is suitable only where the application circuit design accommodates the different thermal response characteristics.

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