Littelfuse 0452.500MRSN Surface Mount Board Fuse Equivalent & Substitute Parts

Part Overview

The Littelfuse 0452.500MRSN is a 500 mA, 125 V AC surface mount board fuse in the NANO²® 452 series. This slow-blow fuse is designed for board-level protection in applications requiring cartridge-style excluded board mount configurations. The part is actively produced and widely stocked, with 923 units available in original packaging. Alternative part numbers within the NANO²® product family provide equivalent electrical performance with variations in packaging format and series designation, enabling flexible procurement and supply chain optimization.

Key Parameters

Parameter	Value
Current Rating	500 mA
Voltage Rating (AC)	125 V
Voltage Rating (DC)	Not specified
Response Time	Slow Blow
Mounting Type	Surface Mount
Package / Case	2-SMD, Square End Block
Physical Dimensions	0.240" L x 0.106" W x 0.106" H (6.10mm x 2.69mm x 2.69mm)
Breaking Capacity @ Rated Voltage	50 A
DC Cold Resistance	0.7 Ohms
Operating Temperature Range	-55°C to 125°C
Approval Agencies	CSA, UR
RoHS Status	ROHS3 Compliant
Moisture Sensitivity Level	1 (Unlimited)

Substitute Part Grouping Explanation

Substitution eligibility for the 0452.500MRSN is determined by strict equivalence across the following critical parameters:

Current Rating: 500 mA (exact match required)
Voltage Rating (AC): 125 V (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)
Physical Dimensions: 0.240" L x 0.106" W x 0.106" H (exact match required)
Breaking Capacity @ Rated Voltage: 50 A (exact match required)
Operating Temperature Range: -55°C to 125°C (exact match required)

All four substitute parts meet these criteria. Variations exist in series designation (NANO²® 449, 452, 454), packaging format (Tape & Reel vs. Cut Tape & Digi-Reel®), approval agency certifications, and minor electrical characteristics (Melting I²t, DC Cold Resistance). These variations do not affect functional equivalence for board-level protection applications.

Parameter Comparison

Parameter	0452.500MRSN (Main)	0449.500MR	0452.500MRL	0452.500NRL	0454.500MR
Manufacturer	Littelfuse Inc.	Littelfuse Inc.	Littelfuse Inc.	Littelfuse Inc.	Littelfuse Inc.
Current Rating (Amps)	500 mA	500 mA	500 mA	500 mA	500 mA
Voltage Rating - AC	125 V	125 V	125 V	125 V	125 V
Voltage Rating - DC	Not specified	125 V	125 V	125 V	125 V
Response Time	Slow Blow	Slow Blow	Slow Blow	Slow Blow	Slow Blow
Mounting Type	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount
Package / Case	2-SMD, Square End Block	2-SMD, Square End Block	2-SMD, Square End Block	2-SMD, Square End Block	2-SMD, Square End Block
Packaging Format	Tape & Reel (TR)	Tape & Reel (TR)	Cut Tape (CT) & Digi-Reel®	Tape & Reel (TR)	Tape & Reel (TR)
Size / Dimension	0.240" L x 0.106" W x 0.106" H (6.10mm x 2.69mm x 2.69mm)	0.240" L x 0.106" W x 0.106" H (6.10mm x 2.69mm x 2.69mm)	0.240" L x 0.106" W x 0.106" H (6.10mm x 2.69mm x 2.69mm)	0.240" L x 0.106" W x 0.106" H (6.10mm x 2.69mm x 2.69mm)	0.240" L x 0.106" W x 0.106" H (6.10mm x 2.69mm x 2.69mm)
Breaking Capacity @ Rated Voltage	50 A	50 A	50 A	50 A	50 A
Melting I²t	0.24	0.258	0.24	0.024	0.24
DC Cold Resistance	0.7 Ohms	0.7633 Ohms	0.7 Ohms	0.7 Ohms	0.7 Ohms
Approval Agency	CSA, UR	cULus	CSA, UR	CSA, UR	CSA, UL
Operating Temperature	-55°C ~ 125°C	-55°C ~ 125°C	-55°C ~ 125°C	-55°C ~ 125°C	-55°C ~ 125°C
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Moisture Sensitivity Level (MSL)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)
Product Status	Active	Active	Active	Active	Active
Inventory Availability	923 Pcs	3142 Pcs	150200 Pcs	3628 Pcs	3400 Pcs

Engineering Selection Recommendations

All four substitute parts are actively produced by Littelfuse Inc. and carry ROHS3 compliance with MSL Level 1 rating. Selection between the main part and substitutes is based on packaging requirements and certification scope:

0452.500MRSN (Main Part): Tape & Reel packaging with CSA and UR certifications. Suitable for standard production environments requiring these specific approval agencies.

0449.500MR: NANO²® 449 series with cULus certification. Provides DC voltage rating specification (125 V DC) not explicitly stated in the main part. Tape & Reel packaging with 3142 units in stock.

0452.500MRL: NANO²® 452 series with CSA and UR certifications matching the main part. Cut Tape & Digi-Reel® packaging format. Highest inventory availability at 150200 units, suitable for high-volume procurement.

0452.500NRL: NANO²® 452 series with CSA and UR certifications. Tape & Reel packaging. Melting I²t value of 0.024 differs from other variants; verify application requirements before selection.

0454.500MR: NANO²® 454 series with CSA and UL certifications. Tape & Reel packaging with 3400 units in stock. UL certification differs from UR certification on the main part.

Frequently Asked Questions (FAQ)

Q: Can I substitute 0452.500MRSN with 0452.500MRL?

A: Yes. Both parts are NANO²® 452 series with identical electrical specifications (500 mA, 125 V AC, 50 A breaking capacity, 0.7 Ohms DC cold resistance). The primary difference is packaging format: 0452.500MRSN uses Tape & Reel, while 0452.500MRL uses Cut Tape & Digi-Reel®. Both are CSA and UR certified. Selection depends on your assembly equipment and procurement volume requirements.

Q: What is the difference between 0452.500MRSN and 0449.500MR?

A: Both parts share identical current rating (500 mA), voltage rating (125 V AC), response time (Slow Blow), and physical dimensions. The 0449.500MR is NANO²® 449 series with cULus certification, while 0452.500MRSN is NANO²® 452 series with CSA and UR certification. The 0449.500MR explicitly specifies 125 V DC rating. Certification requirements and DC voltage specification needs determine which part is appropriate for your application.

Q: Why does 0452.500NRL have a different Melting I²t value?

A: The 0452.500NRL lists Melting I²t as 0.024, while other variants specify 0.24. This parameter affects thermal response characteristics. Verify your application's thermal protection requirements before selecting this part as a substitute.

Q: Are all substitute parts RoHS compliant?

A: Yes. All parts listed—0452.500MRSN, 0449.500MR, 0452.500MRL, 0452.500NRL, and 0454.500MR—are ROHS3 compliant with Moisture Sensitivity Level 1 (Unlimited).

Q: Which substitute has the best inventory availability?

A: The 0452.500MRL has the highest inventory at 150200 units. This part uses Cut Tape & Digi-Reel® packaging and maintains CSA and UR certifications identical to the main part.

Q: Can I use 0454.500MR as a direct replacement?

A: Yes. The 0454.500MR is electrically and mechanically equivalent to 0452.500MRSN. Both use Tape & Reel packaging and share identical current, voltage, breaking capacity, and physical dimensions. The primary difference is series designation (NANO²® 454 vs. 452) and certification scope (CSA, UL vs. CSA, UR). Verify that UL certification meets your application requirements.

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