Littelfuse 0451.100MRSN Surface Mount Board Fuse - Equivalent & Substitute Parts

Part Overview

The Littelfuse 0451.100MRSN is a 100 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-density mounting. The part is active in production with full inventory availability. Substitute parts are identified to support procurement flexibility, design revisions, or supply chain optimization while maintaining equivalent electrical and mechanical performance within specified parameters.

Substiute Parts

0451.100MRSN

Littelfuse Inc.In Stock: 7570451.100MRSN Datasheet

Current PartRFQ

0448.100MR

LittelfuseIn Stock: 336210448.100MR Datasheet

Parametric EquivalentRFQ

0451.100MRL

Littelfuse Inc.In Stock: 203890451.100MRL Datasheet

Parametric EquivalentRFQ

0453.100MR

Littelfuse Inc.In Stock: 37400453.100MR Datasheet

Parametric EquivalentRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitute parts for the 0451.100MRSN are qualified based on the following criteria:

• Current Rating: 100 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)
• 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)
• Moisture Sensitivity Level: 1 (Unlimited) (exact match required)

The following parts meet all substitution criteria and are classified as parametric equivalents:

• Littelfuse 0448.100MR (NANO²® 448 series)
• Littelfuse 0451.100MRL (NANO²® 451 series)
• Littelfuse 0453.100MR (NANO²® 453 series)

Parameter Comparison

Engineering Selection Recommendations

All substitute parts listed are active products from Littelfuse with full regulatory compliance. Selection among the 0451.100MRSN and its equivalents (0448.100MR, 0451.100MRL, 0453.100MR) is based on the following factors:

• All parts meet identical electrical specifications for current rating, AC voltage rating, and response time
• All parts share identical physical dimensions and mounting characteristics
• All parts carry ROHS3 compliance and MSL Level 1 rating
• The 0448.100MR, 0451.100MRL, and 0453.100MR provide DC voltage rating of 125 V, whereas the main part 0451.100MRSN specifies AC only
• Melting I²t values differ between the 0448.100MR (0.00082) and the other parts (0.00138), reflecting different thermal response characteristics within the fast-blow classification
• DC cold resistance varies slightly: 0448.100MR at 2.9 Ohms versus 3.1 Ohms for the main part and other equivalents
• Approval agencies differ: main part carries CSA and UR certifications; substitute parts carry CSA and UL certifications

Selection should be based on specific application requirements regarding DC voltage rating, thermal response characteristics, and required regulatory certifications.

Frequently Asked Questions (FAQ)

Q: Can the 0448.100MR be used as a direct replacement for the 0451.100MRSN?

A: The 0448.100MR meets all core electrical and mechanical substitution criteria. However, it differs in melting I²t (0.00082 vs. 0.00138) and DC cold resistance (2.9 Ohms vs. 3.1 Ohms). These differences may affect thermal response characteristics in specific circuit designs. Verify application requirements before substitution.

Q: What is the difference between the 0451.100MRSN and 0451.100MRL?

A: Both parts are from the NANO²® 451 series and share identical electrical and mechanical specifications. The primary difference is that 0451.100MRL specifies a 125 V DC rating in addition to the 125 V AC rating. The main part 0451.100MRSN specifies AC only. Melting I²t and DC cold resistance are identical between these two parts.

Q: Are all substitute parts RoHS compliant?

A: Yes. All parts listed—0451.100MRSN, 0448.100MR, 0451.100MRL, and 0453.100MR—are ROHS3 compliant and carry MSL Level 1 (Unlimited) moisture sensitivity rating.

Q: Do the substitute parts have the same physical footprint?

A: Yes. All parts share identical dimensions of 0.240" L x 0.106" W x 0.106" H (6.10mm x 2.69mm x 2.69mm) and use the same 2-SMD, Square End Block package. PCB layout and assembly processes remain unchanged.

Q: What regulatory certifications apply to these parts?

A: The main part 0451.100MRSN carries CSA and UR approvals. The substitute parts 0448.100MR, 0451.100MRL, and 0453.100MR carry CSA and UL approvals. Verify that the required certification standard for your application is met by the selected part.

Q: Can these parts be used in DC applications?

A: The main part 0451.100MRSN specifies 125 V AC only. The substitute parts 0448.100MR, 0451.100MRL, and 0453.100MR specify 125 V AC and 125 V DC. For DC applications, use one of the substitute parts that explicitly lists DC voltage rating.