Littelfuse 045101.5MRSN Surface Mount Board Fuse Equivalent & Substitute Parts

Part Overview

The Littelfuse 045101.5MRSN is a 1.5 A 125 V AC surface mount board fuse in the NANO²® 451 series, designed for fast-blow protection in compact 2-SMD square end block packaging. This part is actively manufactured and widely used in electronic equipment requiring reliable overcurrent protection. Alternative part numbers within the Littelfuse NANO²® fuse family provide equivalent electrical performance with variations in packaging format and series designation, enabling procurement flexibility and supply chain continuity.

Key Parameters

Parameter	Value
Current Rating	1.5 A
Voltage Rating (AC)	125 V
Response Time	Fast Blow
Mounting Type	Surface Mount
Package / Case	2-SMD, Square End Block
Breaking Capacity @ Rated Voltage	50 A
Operating Temperature Range	-55°C to 125°C
Size / Dimension	0.240" L x 0.106" W x 0.106" H (6.10mm x 2.69mm x 2.69mm)
RoHS Status	ROHS3 Compliant
Moisture Sensitivity Level (MSL)	1 (Unlimited)

Substitute Part Grouping Explanation

Substitution eligibility for the 045101.5MRSN is determined by the following critical parameters:

Current Rating: 1.5 A (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)
Response Time: Fast Blow (exact match required)
Operating Temperature Range: -55°C to 125°C (exact match required)
Physical Dimensions: 0.240" L x 0.106" W x 0.106" H (exact match required)

All four substitute parts meet these criteria. Variations exist in packaging format (Tape & Reel versus Cut Tape & Digi-Reel®), series designation (NANO²® 448, 451, or 453), and DC voltage rating capability. The 044801.5MR additionally supports 125 V DC operation, while the 045101.5MRSN is specified for AC only.

Parameter Comparison

Parameter	045101.5MRSN (Main)	044801.5MR	045101.5MRL	045101.5NRL	045301.5MR
Manufacturer	Littelfuse Inc.	Littelfuse Inc.	Littelfuse Inc.	Littelfuse Inc.	Littelfuse Inc.
Series	NANO²® 451	NANO²® 448	NANO²® 451	NANO²® 451	NANO²® 453
Current Rating (Amps)	1.5 A	1.5 A	1.5 A	1.5 A	1.5 A
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	Fast Blow	Fast Blow	Fast Blow	Fast Blow	Fast 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)	Cut Tape (CT) & Digi-Reel®	Cut Tape (CT) & Digi-Reel®	Tape & Reel (TR)	Tape & Reel (TR)
Breaking Capacity @ Rated Voltage	50 A	50 A	50 A	50 A	50 A
Melting I²t	0.853	0.9	0.853	0.853	0.853
Operating Temperature	-55°C to 125°C	-55°C to 125°C	-55°C to 125°C	-55°C to 125°C	-55°C to 125°C
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)
DC Cold Resistance	0.063 Ohms	0.06514 Ohms	0.063 Ohms	0.063 Ohms	0.063 Ohms
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
Approval Agency	CSA, UR	CSA, UL, PSE	CSA, PSE, UL	CSA, PSE, UL	CSA, PSE, UL

Engineering Selection Recommendations

All substitute parts are actively manufactured and maintain ROHS3 compliance and MSL 1 rating. Selection between alternatives is based on packaging format and regulatory certification requirements:

045101.5MRL and 045101.5NRL are direct electrical equivalents within the NANO²® 451 series, differing only in packaging format (Cut Tape & Digi-Reel® versus Tape & Reel). Both carry CSA, PSE, and UL certifications and support 125 V DC operation.

044801.5MR belongs to the NANO²® 448 series and carries CSA, UL, and PSE certifications. This part exhibits a slightly higher melting I²t value (0.9 versus 0.853) and marginally higher DC cold resistance (0.06514 versus 0.063 Ohms), with availability in Cut Tape & Digi-Reel® packaging.

045301.5MR is part of the NANO²® 453 series with CSA, PSE, and UL certifications, available in Tape & Reel packaging. Electrical characteristics match the main part exactly.

The 045101.5MRSN is specified for 125 V AC operation only. Substitute parts offering 125 V DC capability provide expanded application flexibility for dual-voltage circuits.

Frequently Asked Questions (FAQ)

Q: Can 045101.5MRL replace 045101.5MRSN in production?

A: Yes. Both parts are electrically identical within the NANO²® 451 series with matching current rating, voltage, response time, and physical dimensions. The difference is packaging format: 045101.5MRL uses Cut Tape & Digi-Reel® while 045101.5MRSN uses Tape & Reel. Assembly equipment compatibility must be confirmed.

Q: What is the difference between 045101.5MRSN and 044801.5MR?

A: Both are 1.5 A 125 V AC fast-blow surface mount fuses in identical 2-SMD square end block packages. The 044801.5MR belongs to the NANO²® 448 series and has a melting I²t of 0.9 compared to 0.853 for the 451 series. The 044801.5MR also supports 125 V DC operation. Regulatory certifications differ slightly (PSE included for 448 series).

Q: Is the 045301.5MR suitable as a substitute?

A: Yes. The 045301.5MR from the NANO²® 453 series matches all critical electrical parameters and physical dimensions. It is available in Tape & Reel packaging and carries CSA, PSE, and UL certifications.

Q: Does packaging format affect electrical performance?

A: No. Tape & Reel (TR) and Cut Tape & Digi-Reel® (CT) packaging formats are logistics and assembly considerations only. Electrical characteristics and performance are identical between parts with the same electrical specifications.

Q: Can I use a substitute part rated for 125 V DC in an AC-only circuit?

A: Yes. Parts rated for both 125 V AC and 125 V DC are backward compatible with AC-only applications. The DC rating indicates expanded capability, not a limitation for AC use.

Q: What certifications apply to all substitute parts?

A: All parts carry CSA certification. UL and PSE certifications are present on all substitutes. The main part 045101.5MRSN carries CSA and UR certifications.

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