Littelfuse 0451.315MRL Surface Mount Fuse Equivalent & Substitute Parts

Part Overview

The Littelfuse 0451.315MRL is a 315 mA, 125 V AC/DC surface mount board fuse in the NANO²® 451 series. This fast-blow fuse is designed for circuit protection in compact 2-SMD, square end block packaging. The part is currently active in production with full inventory availability. Equivalent and substitute parts are identified when design requirements necessitate alternative sourcing, inventory constraints, or series-specific performance characteristics.

Substiute Parts

0451.315MRL

Littelfuse Inc.In Stock: 72030451.315MRL Datasheet

Current PartRFQ

0448.315MR

Littelfuse Inc.In Stock: 103970448.315MR Datasheet

Parametric EquivalentRFQ

0453.315MR

LittelfuseIn Stock: 73340453.315MR Datasheet

Parametric EquivalentRFQ

SF-2410FP0315T-2

Bourns Inc.In Stock: 3131SF-2410FP0315T-2 Datasheet

DirectRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for the 0451.315MRL is determined by the following critical parameters:

• Current Rating: 315 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 to 125°C (exact match required)
• Approval Agency: CSA and/or UL certification (required for regulatory compliance)

All identified substitute parts meet these electrical and mechanical parameters. Variations in DC Cold Resistance and Melting I²t values are within acceptable tolerances for this product category and do not preclude substitution when electrical performance requirements are met.

Parameter Comparison

Engineering Selection Recommendations

All substitute parts listed are active production components with current regulatory certifications (CSA, UL, or cUL). Selection among these equivalents should be based on:

• Inventory availability and lead time requirements
• DC Cold Resistance tolerance requirements for specific circuit designs
• Melting I²t characteristics when thermal response precision is critical
• Manufacturer preference or qualification requirements in existing designs
• Packaging and supply chain considerations

The 0451.315MRL, 0448.315MR, and 0453.315MR are all Littelfuse NANO²® series products with identical electrical ratings and mechanical dimensions. The SF-2410FP0315T-2 from Bourns offers equivalent electrical performance with minor dimensional variation (0.102" vs. 0.106" width and height) and different thermal response characteristics (Melting I²t of 0.1365 versus 0.0311 or 0.0265).

Frequently Asked Questions (FAQ)

Q: Can the 0448.315MR be used as a direct replacement for the 0451.315MRL?

A: Yes. Both parts share identical current rating (315 mA), voltage ratings (125 V AC/DC), response time (Fast Blow), mounting type (Surface Mount), package type (2-SMD, Square End Block), breaking capacity (50 A), and operating temperature range (-55°C to 125°C). Both carry CSA and UL certifications. The primary difference is DC Cold Resistance (0.79 Ohms versus 0.3918 Ohms) and Melting I²t (0.0265 versus 0.0311), which are within acceptable tolerances for this product category.

Q: What is the difference between the Littelfuse NANO²® series parts (0451, 0448, 0453)?

A: All three Littelfuse parts meet identical electrical and mechanical specifications for this 315 mA, 125 V application. The series designation (451, 448, 453) indicates different internal design generations or manufacturing processes. DC Cold Resistance and Melting I²t values vary slightly between series, but all parts are qualified for the same circuit protection function.

Q: Can the Bourns SF-2410FP0315T-2 replace the Littelfuse 0451.315MRL?

A: Yes, from an electrical standpoint. The Bourns part meets all critical electrical parameters: 315 mA current rating, 125 V AC/DC voltage ratings, Fast Blow response, 50 A breaking capacity, and -55°C to 125°C operating temperature. Physical dimensions are nearly identical (0.240" length is the same; width and height are 0.102" versus 0.106"). The Melting I²t value is higher (0.1365 versus 0.0311), indicating different thermal response characteristics. Both parts carry UL certification (Bourns includes cUL). Substitution is valid when thermal response differences are acceptable for the application.

Q: Are all these parts RoHS compliant?

A: Yes. All listed parts are ROHS3 Compliant and carry REACH Unaffected status, meeting current environmental and regulatory requirements.

Q: What is the significance of the different Melting I²t values?

A: Melting I²t describes the thermal energy required to melt the fuse element. Lower values (0.0265, 0.0311) indicate faster thermal response to overcurrent conditions. The Bourns part (0.1365) has a higher Melting I²t, meaning it requires more thermal energy to operate. This difference affects the fuse's response time to transient overcurrent events and should be evaluated against specific circuit protection requirements.

Q: Do these parts have identical physical dimensions?

A: The Littelfuse parts (0451.315MRL, 0448.315MR, 0453.315MR) have identical dimensions: 0.240" L x 0.106" W x 0.106" H. The Bourns SF-2410FP0315T-2 has the same length (0.240") but slightly smaller width and height (0.102" versus 0.106"). This minor dimensional difference is typically not significant for PCB layout, as both fit standard 2-SMD, square end block footprints.