Littelfuse 0451012.MR Surface Mount Fuse – Equivalent & Substitute Parts

Part Overview

The Littelfuse 0451012.MR is a 12 A, 65 V AC/DC surface mount board fuse in the NANO²® 451 series, packaged as a 2-SMD square end block component. This part is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement.

Surface mount fuses in this category serve as overcurrent protection devices in compact form factors, suitable for applications requiring fast-blow response characteristics and board-level integration. The obsolete status of the primary part necessitates identification of active alternatives that maintain electrical and mechanical compatibility.

Key Parameters

Parameter	Value
Current Rating	12 A
Voltage Rating (AC)	65 V
Voltage Rating (DC)	65 V
Response Time	Fast Blow
Mounting Type	Surface Mount
Package / Case	2-SMD, Square End Block
Physical Dimensions	0.240" L × 0.106" W × 0.106" H (6.10mm × 2.69mm × 2.69mm)
Breaking Capacity @ Rated Voltage	50 A
DC Cold Resistance	0.0049 Ohms
Operating Temperature Range	-55°C to 125°C
Approval Agencies	CSA, UL

Substitute Part Grouping Explanation

Substitution eligibility for the 0451012.MR is determined by the following critical parameters:

Electrical Parameters (Must Match):

Current Rating: 12 A
Voltage Rating (AC): 65 V minimum
Voltage Rating (DC): 65 V minimum
Response Time: Fast Blow
Breaking Capacity: 50 A minimum

Mechanical Parameters (Must Match):

Mounting Type: Surface Mount
Package / Case: 2-SMD, Square End Block
Physical Dimensions: 0.240" L × 0.106" W × 0.106" H (6.10mm × 2.69mm × 2.69mm)

Compliance Parameters (Preferred):

Approval Agencies: CSA, UL
RoHS Status: ROHS3 Compliant (preferred for new designs)
Operating Temperature: -55°C to 125°C

Littelfuse parts 0451012.MRL, 0451012.NRL, 0453012.MR, and 0453012.NR meet all electrical and mechanical requirements. The Bourns SF-2410F1200T-2 meets electrical and mechanical requirements with higher voltage and breaking capacity ratings, making it suitable for applications with higher voltage headroom requirements.

Parameter Comparison

Part Number	Manufacturer	Series	Current (A)	Voltage AC (V)	Voltage DC (V)	Response	Breaking Capacity (A)	Melting I²t	DC Resistance (Ω)	Product Status	RoHS Status	Inventory (Pcs)
0451012.MR	Littelfuse Inc.	NANO²® 451	12	65	65	Fast Blow	50	47.97	0.0049	Obsolete	RoHS Non-Compliant	80,300
0451012.MRL	Littelfuse Inc.	NANO²® 451	12	65	65	Fast Blow	50	47.97	0.0049	Active	ROHS3 Compliant	100,100
0451012.NRL	Littelfuse Inc.	NANO²® 451	12	65	65	Fast Blow	50	47.97	0.0049	Active	ROHS3 Compliant	693
0453012.MR	Littelfuse Inc.	NANO²® 453	12	65	65	Fast Blow	50	47.97	0.0049	Active	ROHS3 Compliant	6,105
0453012.NR	Littelfuse Inc.	NANO²® 453	12	65	65	Fast Blow	50	47.97	0.0049	Active	ROHS3 Compliant	895
SF-2410F1200T-2	Bourns Inc.	SinglFuse™ SF-2410F-T	12	86	86	Fast Blow	200	52.91	0.0045	Active	ROHS3 Compliant	2,658

Engineering Selection Recommendations

Primary Substitutes (Littelfuse NANO²® 451 Series):

The 0451012.MRL and 0451012.NRL are direct parametric equivalents to the obsolete 0451012.MR. Both parts maintain identical electrical specifications, mechanical form factor, and thermal characteristics. The 0451012.MRL offers superior inventory availability (100,100 units) and is recommended as the first-choice replacement. Both parts carry ROHS3 compliance and active product status, supporting long-term design continuity.

Alternative Substitutes (Littelfuse NANO²® 453 Series):

The 0453012.MR and 0453012.NR are parametric equivalents from the newer NANO²® 453 series. These parts maintain identical electrical and mechanical specifications while offering ROHS3 compliance and active status. The 0453012.MR provides higher inventory availability (6,105 units) compared to the 0453012.NR (895 units). Selection between 451 and 453 series should be based on design qualification requirements and supply chain considerations.

Cross-Manufacturer Substitute (Bourns SinglFuse™):

The Bourns SF-2410F1200T-2 provides electrical and mechanical compatibility with elevated voltage ratings (86 V AC/DC versus 65 V) and significantly higher breaking capacity (200 A versus 50 A). This part is suitable for applications where higher voltage margin or breaking capacity is beneficial. The slightly lower DC cold resistance (0.0045 Ω versus 0.0049 Ω) and higher melting I²t (52.91 versus 47.97) represent minor performance variations within acceptable engineering tolerances. Physical dimensions differ slightly (0.102" W × 0.102" H versus 0.106" W × 0.106" H), requiring PCB footprint verification before implementation.

Frequently Asked Questions (FAQ)

Q: Can I use 0451012.MRL as a direct replacement for the obsolete 0451012.MR?

A: Yes. The 0451012.MRL is a parametric equivalent with identical electrical ratings (12 A, 65 V AC/DC), response time (Fast Blow), mechanical form factor (2-SMD, Square End Block), and physical dimensions. The primary difference is product status (Active versus Obsolete) and RoHS compliance (ROHS3 Compliant versus Non-Compliant). No design changes are required.

Q: What is the difference between the NANO²® 451 and NANO²® 453 series?

A: Both series maintain identical electrical and mechanical specifications for the 12 A, 65 V rating. The 453 series represents a newer product generation. Selection between series should be based on design qualification history, supply chain availability, and long-term product roadmap considerations. Electrical performance and physical compatibility are equivalent.

Q: Can I substitute the Bourns SF-2410F1200T-2 for the Littelfuse 0451012.MR?

A: The Bourns part is mechanically and electrically compatible with minor considerations. The SF-2410F1200T-2 has higher voltage ratings (86 V AC/DC versus 65 V) and breaking capacity (200 A versus 50 A), providing additional safety margin. Physical dimensions differ slightly (0.102" versus 0.106" width and height), requiring PCB footprint verification. This substitution is suitable for applications where higher voltage headroom is acceptable or beneficial.

Q: What packaging options are available for these substitute parts?

A: All Littelfuse substitutes (0451012.MRL, 0451012.NRL, 0453012.MR, 0453012.NR) are available in Tape & Reel (TR) packaging. The original 0451012.MR was supplied in bulk form. The Bourns SF-2410F1200T-2 is also supplied in Tape & Reel packaging. Confirm packaging requirements with your procurement process before finalizing part selection.

Q: Are all substitute parts RoHS compliant?

A: The Littelfuse substitutes (0451012.MRL, 0451012.NRL, 0453012.MR, 0453012.NR) are ROHS3 Compliant. The Bourns SF-2410F1200T-2 is ROHS3 Compliant. The original 0451012.MR is RoHS Non-Compliant. For applications requiring RoHS compliance, any of the substitute parts are suitable.

Q: What is the inventory status for each substitute part?

A: Current inventory levels are: 0451012.MRL (100,100 units), 0453012.MR (6,105 units), SF-2410F1200T-2 (2,658 units), 0451012.NRL (693 units), and 0453012.NR (895 units). The 0451012.MRL offers the highest availability for immediate procurement needs.

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