Littelfuse 0451.250NRL Surface Mount Board Mount Fuse Equivalent & Substitute Parts

Part Overview

The Littelfuse 0451.250NRL is a 250 mA, 125 V AC/DC surface mount board mount fuse from the NANO²® 451 series. This fast-blow fuse is designed for circuit protection in compact SMD applications with a 2-SMD square end block package. The part is active in production status and widely used in industrial and consumer electronics requiring reliable overcurrent protection.

Equivalent and substitute parts are necessary when the primary part number becomes unavailable, when alternative sourcing is required for supply chain optimization, or when design flexibility allows for functionally compatible alternatives from different manufacturers or series within the same electrical specifications.

Substiute Parts

0451.250NRL

Littelfuse Inc.In Stock: 19270451.250NRL 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

0453.250MR

Littelfuse Inc.In Stock: 101740453.250MR Datasheet

Parametric EquivalentRFQ

SF-2410FP025T-2

Bourns Inc.In Stock: 2011SF-2410FP025T-2 Datasheet

DirectRFQ

Key Parameters

Substitute Part Grouping Explanation

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

• Current Rating: 250 mA (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 ~ 125°C (exact match required)
• Approval Agencies: CSA and/or UL certification (required for regulatory compliance)

All substitute parts listed meet these criteria. Variations in secondary parameters such as DC cold resistance and melting I²t do not disqualify substitution when primary electrical and mechanical specifications are identical.

Parameter Comparison

Engineering Selection Recommendations

All listed substitute parts are active production components with full regulatory compliance. Selection among equivalent parts should be based on:

Littelfuse NANO²® Series (0448.250MR, 0451.250MRL, 0453.250MR): These parts maintain identical electrical specifications and dimensional tolerances to the 0451.250NRL. The 0451.250MRL is functionally identical to the main part, differing only in packaging designation. The 0448.250MR and 0453.250MR represent alternative series within the Littelfuse NANO²® product line with equivalent performance characteristics.

Bourns SinglFuse™ SF-2410FP025T-2: This cross-manufacturer substitute meets all critical electrical and mechanical requirements. It carries cUL and UL certifications and maintains the same current, voltage, and breaking capacity ratings. The dimensional variation (0.102" width and height versus 0.106") remains within the 2-SMD square end block package classification and does not affect PCB footprint compatibility for standard designs.

All parts are ROHS3 compliant, REACH unaffected, and rated for -55°C to 125°C operation, ensuring regulatory and environmental compliance across all substitution options.

Frequently Asked Questions (FAQ)

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

A: Yes. The 0451.250MRL is a parametric equivalent with identical electrical specifications, voltage ratings, current rating, response time, and package configuration. The difference in part number designation reflects packaging or distribution channel variation rather than functional difference.

Q: What is the difference between the Littelfuse NANO²® 448, 451, and 453 series fuses?

A: All three series (0448.250MR, 0451.250MRL, 0453.250MR) meet the same electrical and mechanical specifications for the 250 mA, 125 V AC/DC fast-blow application. Series designation reflects internal design or manufacturing process differences that do not affect substitution eligibility when all rated parameters are identical.

Q: Is the Bourns SF-2410FP025T-2 compatible with the same PCB footprint as the Littelfuse 0451.250NRL?

A: The Bourns part has a dimensional variation of 0.004" in width and height (0.102" versus 0.106"). This minor difference remains within standard 2-SMD square end block package tolerances and is compatible with PCB designs using standard fuse footprints for this package type. Verification with specific PCB layout requirements is recommended for critical applications.

Q: Are all substitute parts certified by the same regulatory agencies?

A: The Littelfuse parts (0448.250MR, 0451.250MRL, 0453.250MR) carry CSA and UL certifications. The Bourns SF-2410FP025T-2 carries cUL and UL certifications. All parts meet UL requirements. CSA and cUL certifications are equivalent for North American regulatory compliance.

Q: What is the significance of DC cold resistance variation among these parts?

A: DC cold resistance values (ranging from 0.5765 Ohms to 1.119 Ohms) represent inherent design characteristics of each fuse element. All values are within acceptable ranges for 250 mA fuses and do not affect substitution eligibility. These variations do not impact circuit protection performance when all electrical ratings are identical.

Q: Can these fuses be used interchangeably in production assembly?

A: Yes, all listed parts are functionally equivalent for the 250 mA, 125 V AC/DC fast-blow application. Production assembly processes using standard SMD placement equipment can accommodate all parts without modification. Verify component tape specifications and reel configurations with your assembly partner to ensure compatibility with existing pick-and-place programming.