Littelfuse 0251.500NRT2 PICO® II 251 500mA 125V Axial Fuse – Equivalent & Substitute Parts

Part Overview

The Littelfuse 0251.500NRT2 is a 500mA, 125V AC/DC board mount axial fuse from the PICO® II 251 series, designed for through-hole PCB applications. This part is classified as obsolete, making equivalent substitute parts necessary for new designs and ongoing production support. The electrical and mechanical specifications remain consistent across the active substitute parts listed, ensuring direct functional compatibility while offering improved product availability and compliance status.

Key Parameters

Parameter	Value
Current Rating	500 mA
Voltage Rating (AC)	125 V
Voltage Rating (DC)	125 V
Response Time	Fast Blow
Fuse Type	Board Mount (Cartridge Style Excluded)
Package / Case	Axial
Mounting Type	Through Hole
Size / Dimension	0.110" Dia x 0.280" L (2.80mm x 7.11mm)
Breaking Capacity @ Rated Voltage	50A AC, 300A DC
Melting I²t	0.0598
DC Cold Resistance	0.302 Ohms
Operating Temperature Range	-55°C ~ 125°C
Approval Agencies	CCC, CSA, cURus, TUV

Substitute Part Grouping Explanation

Substitute parts for the 0251.500NRT2 are grouped based on strict electrical and mechanical parameter equivalence. All substitute parts maintain identical specifications across the following critical parameters:

Current Rating: 500 mA
Voltage Rating: 125 V AC / 125 V DC
Response Time: Fast Blow
Package / Case: Axial
Mounting Type: Through Hole
Physical Dimensions: 0.110" Dia x 0.280" L (2.80mm x 7.11mm)
Breaking Capacity: 50A AC, 300A DC
Melting I²t: 0.0598
DC Cold Resistance: 0.302 Ohms
Operating Temperature: -55°C ~ 125°C
Approval Agencies: CCC, CSA, cURus, TUV

Substitutes differ only in packaging format (Bulk, Cut Tape, or Tape & Reel) and product status. All active substitute parts are ROHS3 compliant and REACH unaffected, whereas the original 0251.500NRT2 is RoHS non-compliant and obsolete.

Parameter Comparison

Part Number	Manufacturer	Product Status	Packaging	Current Rating	Voltage (AC/DC)	Response Time	Breaking Capacity	RoHS Status	Inventory (Pcs)
0251.500NRT2	Littelfuse Inc.	Obsolete	-	500 mA	125V / 125V	Fast Blow	50A AC, 300A DC	RoHS non-compliant	952
0251.500MXL	Littelfuse Inc.	Active	Bulk	500 mA	125V / 125V	Fast Blow	50A AC, 300A DC	ROHS3 Compliant	3488
0251.500HAT1L	Littelfuse Inc.	Active	Cut Tape (CT)	500 mA	125V / 125V	Fast Blow	50A AC, 300A DC	ROHS3 Compliant	893
0251.500MAT1L	Littelfuse Inc.	Active	Cut Tape (CT)	500 mA	125V / 125V	Fast Blow	50A AC, 300A DC	ROHS3 Compliant	8348
0251.500MRT1L	Littelfuse Inc.	Active	Cut Tape (CT)	500 mA	125V / 125V	Fast Blow	50A AC, 300A DC	ROHS3 Compliant	6383
0251.500NAT1L	Littelfuse Inc.	Active	Cut Tape (CT)	500 mA	125V / 125V	Fast Blow	50A AC, 300A DC	ROHS3 Compliant	7125
0251.500NRT1L	Littelfuse	Active	Cut Tape (CT)	500 mA	125V / 125V	Fast Blow	50A AC, 300A DC	ROHS3 Compliant	44501
0251.500PARL	Littelfuse Inc.	Active	Tape & Reel (TR)	500 mA	125V / 125V	Fast Blow	50A AC, 300A DC	ROHS3 Compliant	1123
0251.500PF001L	Littelfuse Inc.	Active	Tape & Reel (TR)	500 mA	125V / 125V	Fast Blow	50A AC, 300A DC	ROHS3 Compliant	906
0251.500PF003L	Littelfuse Inc.	Active	Tape & Reel (TR)	500 mA	125V / 125V	Fast Blow	50A AC, 300A DC	ROHS3 Compliant	931
0251.500PF025L	Littelfuse Inc.	Active	Tape & Reel (TR)	500 mA	125V / 125V	Fast Blow	50A AC, 300A DC	ROHS3 Compliant	1039

Engineering Selection Recommendations

Selection of substitute parts should be based on three primary factors: product status, regulatory compliance, and packaging requirements.

All substitute parts listed are in active production status, ensuring long-term availability and supply chain stability compared to the obsolete 0251.500NRT2. All active substitutes are ROHS3 compliant and REACH unaffected, meeting current environmental and regulatory requirements for new designs and manufacturing operations.

Packaging selection depends on assembly methodology:

Bulk packaging (0251.500MXL) is suitable for manual assembly or low-volume applications.
Cut Tape (CT) packaging (0251.500HAT1L, 0251.500MAT1L, 0251.500MRT1L, 0251.500NAT1L, 0251.500NRT1L) is appropriate for semi-automated pick-and-place operations.
Tape & Reel (TR) packaging (0251.500PARL, 0251.500PF001L, 0251.500PF003L, 0251.500PF025L) is optimized for high-volume automated assembly lines.

The 0251.500NRT1L offers the highest inventory availability (44,501 pcs) in Cut Tape format, providing supply security for production environments. The 0251.500MXL in Bulk format serves as the manufacturer-recommended option for general replacement applications.

Frequently Asked Questions (FAQ)

Q: Can I directly replace 0251.500NRT2 with any of the listed substitute parts?

A: Yes. All substitute parts maintain identical electrical specifications (500mA, 125V AC/DC, Fast Blow response) and mechanical dimensions (0.110" Dia x 0.280" L). The only differences are packaging format and product status. Selection depends on your assembly process and supply chain requirements.

Q: What is the difference between Cut Tape and Tape & Reel packaging?

A: Cut Tape (CT) packaging provides individual component strips suitable for semi-automated assembly equipment. Tape & Reel (TR) packaging supplies components on continuous reels optimized for high-speed automated pick-and-place machines. Bulk packaging provides loose components for manual assembly.

Q: Why is the original 0251.500NRT2 marked as obsolete?

A: The 0251.500NRT2 is obsolete and has been superseded by active alternatives. All substitute parts offer improved compliance status (ROHS3 compliant vs. RoHS non-compliant) and guaranteed long-term availability.

Q: Are all substitute parts certified to the same approval agencies?

A: Yes. All parts, including the original 0251.500NRT2, carry identical certifications: CCC, CSA, cURus, and TUV. Approval agency compliance is maintained across all substitutes.

Q: Which substitute part should I choose for new production designs?

A: For new designs, select based on your manufacturing process: 0251.500MXL (Bulk) for manual assembly, 0251.500NRT1L (Cut Tape) for semi-automated lines, or 0251.500PARL / 0251.500PF series (Tape & Reel) for high-volume automated assembly. All are ROHS3 compliant and actively produced.

Q: Is there a performance difference between the substitute parts?

A: No. All substitute parts are electrically and mechanically identical. Differences are limited to packaging format and inventory availability. Performance characteristics including breaking capacity (50A AC, 300A DC), melting I²t (0.0598), and DC cold resistance (0.302 Ohms) are identical across all parts.

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