Littelfuse 045104.6MR Surface Mount Board Mount Fuse Equivalent & Substitute Parts

Part Overview

The Littelfuse 045104.6MR is a 4.6 A, 125 V AC/DC surface mount board mount fuse from the NANO²® 451 series. This component is classified as obsolete, necessitating identification of active equivalent and substitute parts for new designs and ongoing production requirements. Equivalent parts maintain identical electrical and mechanical specifications, while substitute parts provide functional alternatives within the same application envelope.

Key Parameters

Parameter	Value
Current Rating	4.6 A
Voltage Rating (AC)	125 V
Voltage Rating (DC)	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 ~ 125°C
Size / Dimension	0.240" L x 0.106" W x 0.106" H (6.10mm x 2.69mm x 2.69mm)
Approval Agency	CSA, PSE, UL

Substitute Part Grouping Explanation

Substitution of the 045104.6MR is determined by strict equivalence across the following parameters: current rating (4.6 A), voltage ratings (125 V AC and 125 V DC), response time (Fast Blow), mounting type (Surface Mount), package configuration (2-SMD, Square End Block), breaking capacity (50 A), and operating temperature range (-55°C ~ 125°C). All identified substitutes maintain these core electrical and mechanical specifications. Variations in melting I²t, DC cold resistance, and RoHS compliance status do not preclude substitution when the primary protective function parameters remain constant.

Parameter Comparison

Part Number	Manufacturer	Series	Current Rating (A)	Voltage AC (V)	Voltage DC (V)	Response Time	Breaking Capacity (A)	Melting I²t	DC Cold Resistance (Ω)	Product Status	RoHS Status
045104.6MR	Littelfuse	NANO²® 451	4.6	125	125	Fast Blow	50	2.469	0.02	Obsolete	RoHS non-compliant
044804.6MR	Littelfuse	NANO²® 448	4.6	125	125	Fast Blow	50	2.3	0.021	Active	ROHS3 Compliant
045104.6MRL	Littelfuse	NANO²® 451	4.6	125	125	Fast Blow	50	2.469	0.02	Active	ROHS3 Compliant
045104.6NRL	Littelfuse	NANO²® 451	4.6	125	125	Fast Blow	50	2.469	0.02	Active	ROHS3 Compliant
045304.6MR	Littelfuse	NANO²® 453	4.6	125	125	Fast Blow	50	2.469	0.02	Active	ROHS3 Compliant
045304.6NR	Littelfuse	NANO²® 453	4.6	125	125	Fast Blow	50	2.469	0.02	Active	ROHS3 Compliant
SF-2410FP350T-2	Bourns	SinglFuse™ SF-2410FP-T	4.6	125	125	Fast Blow	50	2.695	0.029	Active	ROHS3 Compliant
SF-2410HI350T-2	Bourns	SinglFuse™ SF-2410HI-T	4.6	125	125	Fast Blow	50	24.908	0.0196	Active	ROHS3 Compliant

Engineering Selection Recommendations

For new designs and production transitions, Littelfuse 045104.6MRL or 045104.6NRL are the primary recommended substitutes. Both parts maintain identical electrical characteristics to the obsolete 045104.6MR while offering active product status and ROHS3 compliance. The 045104.6MRL is available in Cut Tape & Digi-Reel® packaging with 9535 units in stock, providing superior availability. The 045104.6NRL is available in Tape & Reel packaging with 1009 units in stock.

Alternative Littelfuse options include 044804.6MR (NANO²® 448 series, active status, 1480 units in stock), 045304.6MR (NANO²® 453 series, active status, 5450 units in stock), and 045304.6NR (NANO²® 453 series, active status, 1020 units in stock). All Littelfuse substitutes maintain CSA, PSE, and UL certifications.

Bourns SinglFuse™ parts SF-2410FP350T-2 and SF-2410HI350T-2 provide cross-manufacturer alternatives with active product status and ROHS3 compliance. Both are certified to cUL and UL standards. The SF-2410FP350T-2 offers 2975 units in stock, while SF-2410HI350T-2 provides 2814 units. Note that SF-2410HI350T-2 carries REACH Affected status, whereas all Littelfuse alternatives are REACH Unaffected.

Frequently Asked Questions (FAQ)

Q: Can 045104.6MRL directly replace 045104.6MR in existing designs?

A: Yes. The 045104.6MRL maintains identical electrical specifications (4.6 A, 125 V AC/DC, Fast Blow response) and mechanical dimensions (0.240" L x 0.106" W x 0.106" H). The primary difference is product status (active vs. obsolete) and RoHS compliance. Packaging differs (Cut Tape & Digi-Reel® vs. standard), but the component itself is functionally equivalent.

Q: What is the difference between Littelfuse NANO²® series variants (448, 451, 453)?

A: All three series maintain the same electrical and mechanical specifications for the 4.6 A, 125 V rating. Series designation reflects internal design generation. For the 4.6 A, 125 V application, all series are electrically interchangeable based on the provided parameters.

Q: Are Bourns SinglFuse™ parts compatible with Littelfuse NANO²® footprints?

A: Yes, for the specified application. Both Bourns parts (SF-2410FP350T-2 and SF-2410HI350T-2) maintain the same 2-SMD, Square End Block package configuration, identical current and voltage ratings (4.6 A, 125 V AC/DC), and equivalent physical dimensions (0.240" L x 0.102" W x 0.102" H for Bourns vs. 0.240" L x 0.106" W x 0.106" H for Littelfuse). Minor dimensional variation in width and height (0.004" difference) remains within standard PCB layout tolerances for surface mount applications.

Q: What does melting I²t variation indicate?

A: Melting I²t represents the thermal energy required to melt the fuse element. Variations (ranging from 2.3 to 24.908 in the provided parts) indicate different internal fuse element designs. All parts maintain the same 4.6 A current rating and Fast Blow response classification. The SF-2410HI350T-2 exhibits significantly higher I²t (24.908), indicating a different thermal response profile while maintaining the same current threshold.

Q: Should I consider REACH status when selecting a substitute?

A: REACH status is provided for regulatory tracking purposes. The 045104.6MR and all Littelfuse substitutes are REACH Unaffected. The Bourns SF-2410HI350T-2 is REACH Affected. Selection should account for supply chain and regulatory requirements specific to your application region and customer base.

Q: What packaging options are available?

A: Littelfuse substitutes are available in three packaging formats: Tape & Reel (TR), Cut Tape (CT) & Digi-Reel®, and standard packaging. Bourns parts are supplied in Tape & Reel (TR) format. Packaging selection depends on production volume and assembly equipment compatibility. All packaging options contain the same electrical component.

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