Equivalent & Substitute Parts for 0451003.NRL

Part Overview

The 0451003.NRL is a 3 A, 125 V AC/DC surface mount board mount fuse manufactured by Littelfuse Inc. in the NANO²® 451 series. This fast-blow fuse is designed for circuit protection in applications requiring compact, high-reliability surface mount solutions. The part is active in production with 10,263 units in stock. Alternative part numbers may be required due to packaging availability, inventory constraints, or specific application requirements for different response characteristics or manufacturer preferences.

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
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)
RoHS Status	ROHS3 Compliant
Approval Agencies	CSA, PSE, UL

Substitute Part Grouping Explanation

Substitute parts for the 0451003.NRL are grouped based on strict electrical and mechanical parameter matching:

Parametric Equivalents (Littelfuse NANO²® Series): Parts 0448003.MR, 0451003.MRL, and 0453003.MR maintain identical electrical specifications (3 A, 125 V AC/DC, fast-blow response, 50 A breaking capacity) and mechanical compatibility (2-SMD, Square End Block package, 6.10mm x 2.69mm x 2.69mm dimensions). These parts differ only in packaging format (Tape & Reel vs. Cut Tape & Digi-Reel®) and minor variations in melting I²t and DC cold resistance within acceptable tolerances for the application category.

Direct Manufacturer Equivalents (Bourns SinglFuse™ Series): Parts SF-2410FP300T-2 and SF-2410HI300T-2 from Bourns Inc. match the core electrical parameters (3 A, 125 V AC/DC, fast-blow response, 50 A breaking capacity) and mechanical form factor (2-SMD, Square End Block). Dimensional variation is minimal (0.102" width/height vs. 0.106"), and both are approved to UL and cUL standards. The SF-2410HI300T-2 exhibits significantly higher melting I²t (24.99 vs. 1.65), indicating different thermal response characteristics suitable for specific application requirements.

Parameter Comparison

Parameter	0451003.NRL	0448003.MR	0451003.MRL	0453003.MR	SF-2410FP300T-2	SF-2410HI300T-2
Manufacturer	Littelfuse Inc.	Littelfuse Inc.	Littelfuse Inc.	Littelfuse Inc.	Bourns Inc.	Bourns Inc.
Current Rating (A)	3	3	3	3	3	3
Voltage Rating AC (V)	125	125	125	125	125	125
Voltage Rating DC (V)	125	125	125	125	125	125
Response Time	Fast Blow	Fast Blow	Fast Blow	Fast Blow	Fast Blow	Fast Blow
Breaking Capacity @ Rated Voltage (A)	50	50	50	50	50	50
Mounting Type	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount
Package / Case	2-SMD, Square End Block	2-SMD, Square End Block	2-SMD, Square End Block	2-SMD, Square End Block	2-SMD, Square End Block	2-SMD, Square End Block
Length (mm)	6.10	6.10	6.10	6.10	6.10	6.10
Width (mm)	2.69	2.69	2.69	2.69	2.59	2.59
Height (mm)	2.69	2.69	2.69	2.69	2.59	2.59
Operating Temperature Range (°C)	-55 to 125	-55 to 125	-55 to 125	-55 to 125	-55 to 125	-55 to 125
Melting I²t	1.65	1.72	1.65	1.65	1.548	24.99
DC Cold Resistance (Ohms)	0.0227	0.02445	0.0227	0.0227	0.036	0.0228
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Approval Agencies	CSA, PSE, UL	CSA, UL, PSE	CSA, PSE, UL	CSA, PSE, UL	cUL, UL	cUL, UL

Engineering Selection Recommendations

All listed substitute parts maintain active product status and meet the core electrical and mechanical requirements for direct substitution in applications designed for the 0451003.NRL.

Littelfuse NANO²® Series (0448003.MR, 0451003.MRL, 0453003.MR): These parts are recommended for applications requiring identical thermal response characteristics and full compliance with CSA, PSE, and UL certifications. The 0451003.MRL offers the highest inventory availability (30,200 units) and is functionally identical to the 0451003.NRL, differing only in packaging format (Cut Tape & Digi-Reel® vs. Tape & Reel). The 0453003.MR provides the largest stock position (56,556 units) among all alternatives.

Bourns SinglFuse™ Series (SF-2410FP300T-2, SF-2410HI300T-2): These parts are suitable for applications where Bourns manufacturer preference or cUL/UL certification is specified. The SF-2410FP300T-2 exhibits lower melting I²t (1.548) compared to the 0451003.NRL (1.65), indicating faster thermal response. The SF-2410HI300T-2 provides significantly higher melting I²t (24.99), suitable for applications requiring slower thermal response or higher inrush current tolerance. Note that SF-2410HI300T-2 carries REACH Affected status, whereas all other parts are REACH Unaffected.

Frequently Asked Questions (FAQ)

Q: Can 0451003.MRL be used as a direct replacement for 0451003.NRL?

A: Yes. Both parts are from the Littelfuse NANO²® 451 series with identical electrical specifications (3 A, 125 V AC/DC, fast-blow response), mechanical dimensions (6.10mm x 2.69mm x 2.69mm), and certifications (CSA, PSE, UL). The only difference is packaging format: 0451003.NRL is supplied in Tape & Reel, while 0451003.MRL is supplied in Cut Tape & Digi-Reel®.

Q: What is the difference between the Littelfuse and Bourns fuses?

A: All parts meet identical electrical and mechanical specifications. Littelfuse NANO²® parts (0448003.MR, 0451003.MRL, 0453003.MR) and Bourns SinglFuse™ parts (SF-2410FP300T-2, SF-2410HI300T-2) differ in manufacturer, series designation, and minor variations in melting I²t and DC cold resistance. Bourns parts have slightly smaller cross-sectional dimensions (2.59mm vs. 2.69mm width/height) but maintain the same 6.10mm length and 2-SMD form factor.

Q: Why does SF-2410HI300T-2 have a much higher melting I²t value?

A: The SF-2410HI300T-2 is designed with different thermal characteristics, resulting in a melting I²t of 24.99 compared to 1.65 for the 0451003.NRL. This indicates slower thermal response and higher tolerance to inrush currents or transient overcurrent conditions. Selection between fast-response (lower I²t) and slow-response (higher I²t) variants depends on specific application requirements for circuit protection timing.

Q: Are there any compliance differences between these parts?

A: All parts are ROHS3 compliant. Littelfuse parts carry CSA, PSE, and UL approvals. Bourns parts carry cUL and UL approvals. The SF-2410HI300T-2 is REACH Affected, while all other parts are REACH Unaffected. Application requirements for specific regional certifications should determine part selection.

Q: Can these fuses be used interchangeably on the same PCB?

A: Yes, all parts share the same 2-SMD, Square End Block package and 6.10mm length. Bourns parts have slightly smaller cross-sectional dimensions (0.102" vs. 0.106" width/height), which may require minor PCB pad adjustments. Mechanical fit should be verified during design validation.

Q: What packaging options are available?

A: The 0451003.NRL is supplied in Tape & Reel (TR). Alternatives include Cut Tape & Digi-Reel® (0448003.MR, 0451003.MRL) and Tape & Reel (0453003.MR, SF-2410FP300T-2, SF-2410HI300T-2). Packaging selection depends on manufacturing process requirements and volume needs.

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