Littelfuse 0451003.NR Surface Mount Fuse Equivalent & Substitute Parts

Part Overview

The Littelfuse 0451003.NR is a 3 A, 125 V AC/DC board mount surface 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 characteristics suitable for circuit protection applications requiring 3 A rated current at 125 V AC or DC operating conditions.

Key Parameters

Parameter	Value
Current Rating	3 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
Breaking Capacity @ Rated Voltage	50 A
Operating Temperature Range	-55°C to 125°C
Size / Dimension	0.240" L x 0.106" W x 0.106" H (6.10mm x 2.69mm x 2.69mm)

Substitute Part Grouping Explanation

Substitution for the 0451003.NR is determined by strict equivalence across the following critical parameters:

Current Rating: 3 A (exact match required)
Voltage Rating: 125 V AC and 125 V DC (exact match required)
Response Time: Fast Blow (exact match required)
Mounting Type: Surface Mount (exact match required)
Package / Case: 2-SMD, Square End Block (exact match required)
Breaking Capacity @ Rated Voltage: 50 A (exact match required)
Operating Temperature Range: -55°C to 125°C (exact match required)

All substitute parts listed maintain these electrical and mechanical specifications. Variations in secondary parameters such as melting I²t, DC cold resistance, and RoHS compliance status do not affect functional substitutability but may influence design considerations for specific applications.

Parameter Comparison

Part Number	Manufacturer	Series	Current Rating	Voltage AC/DC	Response Time	Package	Breaking Capacity	Operating Temp	Product Status	RoHS Status	Inventory
0451003.NR	Littelfuse Inc.	NANO²® 451	3 A	125 V / 125 V	Fast Blow	2-SMD, Square End Block	50 A	-55°C ~ 125°C	Obsolete	RoHS non-compliant	887 Pcs
0448003.MR	Littelfuse Inc.	NANO²® 448	3 A	125 V / 125 V	Fast Blow	2-SMD, Square End Block	50 A	-55°C ~ 125°C	Active	ROHS3 Compliant	17025 Pcs
0451003.MRL	Littelfuse Inc.	NANO²® 451	3 A	125 V / 125 V	Fast Blow	2-SMD, Square End Block	50 A	-55°C ~ 125°C	Active	ROHS3 Compliant	30200 Pcs
0451003.NRL	Littelfuse Inc.	NANO²® 451	3 A	125 V / 125 V	Fast Blow	2-SMD, Square End Block	50 A	-55°C ~ 125°C	Active	ROHS3 Compliant	10263 Pcs
0453003.MR	Littelfuse Inc.	NANO²® 453	3 A	125 V / 125 V	Fast Blow	2-SMD, Square End Block	50 A	-55°C ~ 125°C	Active	ROHS3 Compliant	56556 Pcs
0453003.NR	Littelfuse Inc.	NANO²® 453	3 A	125 V / 125 V	Fast Blow	2-SMD, Square End Block	50 A	-55°C ~ 125°C	Active	ROHS3 Compliant	668 Pcs
SF-2410FP300T-2	Bourns Inc.	SinglFuse™ SF-2410FP-T	3 A	125 V / 125 V	Fast Blow	2-SMD, Square End Block	50 A	-55°C ~ 125°C	Active	ROHS3 Compliant	2631 Pcs
SF-2410HI300T-2	Bourns Inc.	SinglFuse™ SF-2410HI-T	3 A	125 V / 125 V	Fast Blow	2-SMD, Square End Block	50 A	-55°C ~ 125°C	Active	ROHS3 Compliant	3392 Pcs

Engineering Selection Recommendations

Littelfuse NANO²® Series (0448003.MR, 0451003.MRL, 0451003.NRL, 0453003.MR, 0453003.NR)

All Littelfuse substitute parts maintain identical electrical and mechanical specifications to the 0451003.NR. The primary distinction is product status: all listed Littelfuse alternatives are active production parts with ROHS3 compliance, whereas the original 0451003.NR is obsolete and RoHS non-compliant. The 0451003.MRL and 0451003.NRL variants are from the same NANO²® 451 series as the original part, providing the closest functional equivalence. The 0448003.MR and 0453003.MR/NR variants represent alternative series within the Littelfuse NANO²® product line with identical performance characteristics.

Bourns SinglFuse™ Series (SF-2410FP300T-2, SF-2410HI300T-2)

The Bourns SF-2410FP300T-2 and SF-2410HI300T-2 are cross-manufacturer substitutes that meet all critical electrical and mechanical parameters. Both parts are active production items with ROHS3 compliance. Physical dimensions show minor variation (0.102" width and height versus 0.106"), remaining within the 2-SMD square end block package classification. Both parts carry UL and cUL certifications, matching the approval agency requirements of the original part.

For applications requiring RoHS3 compliance and active production support, any of the listed substitute parts are functionally equivalent. Selection should prioritize parts with highest inventory availability and shortest lead times for procurement optimization.

Frequently Asked Questions (FAQ)

Q: Can the 0451003.NR be directly replaced with any of the listed substitute parts?

A: Yes. All listed substitute parts maintain identical current rating (3 A), voltage rating (125 V AC/DC), response time (fast blow), mounting type (surface mount), package configuration (2-SMD square end block), breaking capacity (50 A), and operating temperature range (-55°C to 125°C). Direct substitution is supported without circuit modification.

Q: What is the difference between Littelfuse NANO²® series variants (451, 448, 453)?

A: The series designation indicates different product generations within the Littelfuse NANO²® line. All variants listed maintain identical electrical and mechanical specifications for the 3 A, 125 V application. Series differences do not affect functional substitutability.

Q: Are there packaging differences between the substitute parts?

A: Packaging format differs (Cut Tape, Digi-Reel®, or Tape & Reel), but the component package itself (2-SMD square end block) remains consistent across all parts. Packaging format selection depends on procurement volume and assembly process requirements, not functional compatibility.

Q: Why is the original 0451003.NR marked as obsolete?

A: The 0451003.NR is classified as obsolete due to product lifecycle management by Littelfuse. Active production alternatives with identical specifications are available, including the 0451003.MRL and 0451003.NRL from the same NANO²® 451 series.

Q: What is the significance of RoHS compliance status differences?

A: The original 0451003.NR is RoHS non-compliant, while all substitute parts are ROHS3 compliant. For applications subject to RoHS regulations or customer requirements, ROHS3-compliant alternatives must be selected. Functional performance is not affected by RoHS status.

Q: Can Bourns SinglFuse™ parts replace Littelfuse NANO²® parts?

A: Yes. The Bourns SF-2410FP300T-2 and SF-2410HI300T-2 meet all critical electrical and mechanical specifications. Cross-manufacturer substitution is supported. Minor physical dimension variations (0.102" versus 0.106" width/height) remain within the 2-SMD square end block package specification.

Q: What approval agencies certify these fuse parts?

A: The original 0451003.NR carries CSA, PSE, and UL certifications. Littelfuse substitutes maintain CSA, PSE, and UL certifications. Bourns substitutes carry cUL and UL certifications. All parts meet recognized safety standards for board mount fuse applications.

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