Littelfuse 0449.750MR Surface Mount Board Mount Fuse Equivalent & Substitute Parts

Part Overview

The Littelfuse 0449.750MR is a 750 mA, 125 V AC/DC surface mount board mount fuse in the NANO²® 449 series. This slow blow fuse is designed for circuit protection in applications requiring 2-SMD, square end block packaging with a breaking capacity of 50A at rated voltage. The part is active in production status and widely used in industrial and commercial electronic equipment where reliable overcurrent protection is essential. Equivalent and substitute parts are identified to support design flexibility, inventory management, and supply chain continuity.

Substiute Parts

0449.750MR

Littelfuse Inc.In Stock: 17420449.750MR Datasheet

Current PartRFQ

0452.750MRL

Littelfuse Inc.In Stock: 993500452.750MRL Datasheet

Parametric EquivalentRFQ

0454.750MR

LittelfuseIn Stock: 52890454.750MR Datasheet

Parametric EquivalentRFQ

0454.750NR

Littelfuse Inc.In Stock: 10310454.750NR Datasheet

Parametric EquivalentRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitute parts for the 0449.750MR are qualified based on the following critical parameters that must remain constant:

• Current Rating: 750 mA (exact match required)
• Voltage Rating: 125 V AC and 125 V DC (exact match required)
• Response Time: Slow 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: 50A (exact match required)
• Operating Temperature Range: -55°C ~ 125°C (exact match required)
• Physical Dimensions: 0.240" L x 0.106" W x 0.106" H (exact match required)
• RoHS Compliance: ROHS3 Compliant (exact match required)
• MSL Rating: 1 (Unlimited) (exact match required)

The substitute parts identified—0452.750MRL, 0454.750MR, and 0454.750NR—meet all these critical electrical and mechanical parameters. Variations in DC Cold Resistance, Melting I²t values, and approval agency certifications do not affect functional substitutability within the specified parameter constraints.

Parameter Comparison

Engineering Selection Recommendations

All three substitute parts—0452.750MRL, 0454.750MR, and 0454.750NR—are functionally equivalent to the 0449.750MR based on matching electrical and mechanical specifications. Selection among these parts should be based on the following factors:

Approval Agency Certifications: The 0449.750MR carries cULus certification. The 0452.750MRL is certified by CSA and UR. The 0454.750MR and 0454.750NR are certified by CSA and UL. Verify that the selected substitute meets the specific regulatory requirements of your application and target market.

Product Status: All parts maintain active production status, ensuring continued availability and supply chain stability.

Compliance: All substitute parts are ROHS3 compliant and REACH unaffected, meeting environmental and regulatory standards equivalent to the main part.

Inventory Availability: The 0452.750MRL offers the highest inventory level (99,300 pcs), followed by 0454.750MR (5,200 pcs) and 0454.750NR (925 pcs). The main part 0449.750MR has 1,676 pcs in stock.

Frequently Asked Questions (FAQ)

Q: Can the 0452.750MRL, 0454.750MR, or 0454.750NR be used as direct replacements for the 0449.750MR?

A: Yes. All three parts are parametric equivalents with identical current ratings (750 mA), voltage ratings (125 V AC/DC), response time (slow blow), mounting type (surface mount), package configuration (2-SMD, square end block), breaking capacity (50A), operating temperature range (-55°C ~ 125°C), and physical dimensions (0.240" L x 0.106" W x 0.106" H). They are electrically and mechanically interchangeable within the specified parameter constraints.

Q: What are the differences between the substitute parts?

A: The primary differences are the series designation (NANO²® 449, 452, or 454), DC cold resistance values (0.408 Ohms for 0449.750MR versus 0.36 Ohms for the substitutes), melting I²t values (0.847 for 0449.750MR versus 0.904 for the substitutes), and approval agency certifications (cULus for 0449.750MR; CSA/UR for 0452.750MRL; CSA/UL for 0454.750MR and 0454.750NR). These variations do not affect functional substitutability for applications within the specified electrical and mechanical parameters.

Q: Are there any packaging or handling differences?

A: All parts are supplied in Tape & Reel (TR) packaging with MSL rating 1 (Unlimited), indicating no moisture sensitivity restrictions. Handling and storage procedures are equivalent across all parts.

Q: Which substitute part should I select for new designs?

A: Selection should be based on regulatory certification requirements for your target market and application. Verify that the approval agency certifications (cULus, CSA, UR, or UL) align with your design standards and regional compliance requirements. All parts are functionally equivalent and suitable for new designs meeting the specified parameter criteria.

Q: Can I mix these parts in the same production batch?

A: Yes, provided your application and regulatory framework accept the different approval agency certifications. All parts meet identical electrical and mechanical specifications and are physically interchangeable in the same PCB footprint.