Littelfuse 0451.250MRSN Surface Mount Board Fuse - Equivalent & Substitute Parts

Part Overview

The Littelfuse 0451.250MRSN is a 250 mA, 125 V AC surface mount board fuse in the NANO²® 451 series. This fast-blow fuse is designed for board-level circuit protection in applications requiring compact, high-reliability protection. The part is active in production with full RoHS3 compliance and CSA/UR approvals. Substitute parts are identified to support design flexibility, inventory optimization, and supply chain continuity while maintaining equivalent electrical and mechanical performance.

Substiute Parts

0451.250MRSN

Littelfuse Inc.In Stock: 8850451.250MRSN Datasheet

Current PartRFQ

0448.250MR

Littelfuse Inc.In Stock: 102340448.250MR Datasheet

Parametric EquivalentRFQ

0451.250MRL

Littelfuse Inc.In Stock: 204240451.250MRL Datasheet

Parametric EquivalentRFQ

0451.250NRL

Littelfuse Inc.In Stock: 19270451.250NRL Datasheet

Parametric EquivalentRFQ

0453.250MR

Littelfuse Inc.In Stock: 101740453.250MR Datasheet

Parametric EquivalentRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for the 0451.250MRSN is determined by strict equivalence across the following critical parameters:

• Current Rating: 250 mA (exact match required)
• Voltage Rating - AC: 125 V (exact match required)
• Mounting Type: Surface Mount (exact match required)
• Package / Case: 2-SMD, Square End Block (exact match required)
• Physical Dimensions: 0.240" L x 0.106" W x 0.106" H (exact match required)
• Response Time: Fast Blow (exact match required)
• Breaking Capacity @ Rated Voltage: 50A (exact match required)
• Operating Temperature Range: -55°C ~ 125°C (exact match required)
• RoHS Status: ROHS3 Compliant (exact match required)
• Approval Agencies: CSA and/or UL certification (required)

All identified substitute parts meet these criteria. Differences in DC voltage rating capability, melting I²t values, and DC cold resistance do not disqualify substitution when AC voltage rating and current rating are identical.

Parameter Comparison

Engineering Selection Recommendations

All substitute parts listed are active production components with full RoHS3 compliance and appropriate regulatory approvals (CSA and/or UL). Selection among these equivalents may be based on:

• Inventory availability: 0451.250MRL offers the highest stock level (20,400 pcs), followed by 0448.250MR (10,200 pcs) and 0453.250MR (10,100 pcs).
• Series consistency: 0451.250MRL and 0451.250NRL maintain the same NANO²® 451 series as the primary part.
• DC voltage capability: 0448.250MR, 0451.250MRL, 0451.250NRL, and 0453.250MR all support 125 V DC in addition to 125 V AC, providing broader application flexibility.
• Approval agency preference: All parts carry CSA approval; UL approval is available on all substitutes except the primary part.

Frequently Asked Questions (FAQ)

Q: Can 0451.250MRL be used as a direct replacement for 0451.250MRSN?

A: Yes. Both parts share identical current rating (250 mA), AC voltage rating (125 V), response time (Fast Blow), package type (2-SMD, Square End Block), physical dimensions, breaking capacity (50A), melting I²t (0.0158), DC cold resistance (0.5765 Ohms), and operating temperature range (-55°C ~ 125°C). Both are ROHS3 compliant and carry CSA approval. The primary difference is that 0451.250MRL adds 125 V DC rating capability and UL approval.

Q: What is the difference between 0448.250MR and 0451.250MRL?

A: Both parts are electrically equivalent for AC applications (250 mA, 125 V AC, Fast Blow, 50A breaking capacity). The primary differences are: 0448.250MR belongs to the NANO²® 448 series with melting I²t of 0.0152 and DC cold resistance of 1.05 Ohms, while 0451.250MRL belongs to the NANO²® 451 series with melting I²t of 0.0158 and DC cold resistance of 0.5765 Ohms. Both support 125 V DC and carry CSA/UL approvals.

Q: Are all substitute parts in the same physical package?

A: Yes. All parts use the 2-SMD, Square End Block package with identical dimensions of 0.240" L x 0.106" W x 0.106" H (6.10mm x 2.69mm x 2.69mm). They are mechanically interchangeable on the PCB.

Q: Does the primary part 0451.250MRSN support DC voltage?

A: The primary part 0451.250MRSN is rated for 125 V AC only. No DC voltage rating is specified. All substitute parts (0448.250MR, 0451.250MRL, 0451.250NRL, 0453.250MR) support both 125 V AC and 125 V DC.

Q: Which substitute part has the best inventory availability?

A: 0451.250MRL has the highest inventory level at 20,400 pcs, followed by 0448.250MR at 10,200 pcs and 0453.250MR at 10,100 pcs.

Q: Are all parts RoHS3 compliant?

A: Yes. The primary part 0451.250MRSN and all substitute parts (0448.250MR, 0451.250MRL, 0451.250NRL, 0453.250MR) are ROHS3 compliant with MSL rating of 1 (Unlimited).