Littelfuse 0251004.PAT1L Board Mount Axial Fuse Equivalent & Substitute Parts

Part Overview

The Littelfuse 0251004.PAT1L is a 4 A, 125 V AC/DC board mount axial fuse from the PICO® II 251 series. This fast-blow fuse is designed for through-hole mounting applications requiring reliable overcurrent protection in industrial and commercial electronics. The part is currently active in production with full regulatory compliance across multiple approval agencies. Substitute parts are identified based on identical electrical and mechanical specifications, with variations limited to packaging format and inventory availability.

Key Parameters

Parameter	Value
Current Rating	4 A
Voltage Rating (AC)	125 V
Voltage Rating (DC)	125 V
Response Time	Fast Blow
Mounting Type	Through Hole
Fuse Type	Board Mount (Cartridge Style Excluded)
Package / Case	Axial
Breaking Capacity (AC)	50 A
Breaking Capacity (DC)	300 A
Melting I²t	2.45
Size / Dimension	0.110" Dia x 0.280" L (2.80mm x 7.11mm)
DC Cold Resistance	0.0204 Ohms
Operating Temperature Range	-55°C ~ 125°C
Series	PICO® II 251

Substitute Part Grouping Explanation

All substitute parts for the 0251004.PAT1L maintain identical electrical and mechanical specifications across the following critical parameters:

Current Rating: 4 A
Voltage Rating: 125 V AC / 125 V DC
Response Time: Fast Blow
Breaking Capacity: 50 A AC, 300 A DC
Melting I²t: 2.45
Physical Dimensions: 0.110" Dia x 0.280" L (2.80mm x 7.11mm)
DC Cold Resistance: 0.0204 Ohms
Mounting Type: Through Hole
Package / Case: Axial

Substitution differences are limited to packaging format (Tape & Box versus Cut Tape) and inventory levels. All parts are manufactured by Littelfuse Inc., belong to the PICO® II 251 series, and maintain active product status with full regulatory compliance.

Parameter Comparison

Part Number	Manufacturer	Current Rating	Voltage (AC/DC)	Response Time	Breaking Capacity (AC/DC)	Melting I²t	Packaging	Inventory (Pcs)	RoHS Status	REACH Status
0251004.PAT1L	Littelfuse Inc.	4 A	125 V / 125 V	Fast Blow	50 A / 300 A	2.45	Tape & Box (TB)	779	ROHS3 Compliant	REACH Unaffected
0251004.HAT1L	Littelfuse Inc.	4 A	125 V / 125 V	Fast Blow	50 A / 300 A	2.45	Cut Tape (CT)	752	ROHS3 Compliant	REACH Unaffected
0251004.MAT1L	Littelfuse Inc.	4 A	125 V / 125 V	Fast Blow	50 A / 300 A	2.45	Cut Tape (CT)	2305	ROHS3 Compliant	REACH Unaffected
0251004.NAT1L	Littelfuse Inc.	4 A	125 V / 125 V	Fast Blow	50 A / 300 A	2.45	Cut Tape (CT)	5839	ROHS3 Compliant	REACH Affected

Engineering Selection Recommendations

All four part numbers are functionally equivalent for board mount axial fuse applications requiring 4 A protection at 125 V AC/DC with fast-blow response characteristics. Selection between these parts should be based on:

Packaging Requirements: The 0251004.PAT1L is supplied in Tape & Box format, suitable for mixed-volume orders and manual assembly workflows. The 0251004.HAT1L, 0251004.MAT1L, and 0251004.NAT1L are supplied in Cut Tape format, optimized for automated pick-and-place assembly and high-volume production environments.

Regulatory Compliance: All parts maintain ROHS3 compliance. The 0251004.NAT1L is designated as REACH Affected, while the remaining parts are REACH Unaffected. This distinction may influence material sourcing and supply chain documentation requirements depending on end-use geography and regulatory jurisdiction.

Inventory Availability: The 0251004.NAT1L offers the highest stock level at 5,839 pieces, followed by 0251004.MAT1L at 2,305 pieces. Selection based on inventory availability should align with production scheduling and supply chain lead-time requirements.

Frequently Asked Questions (FAQ)

Q: Can 0251004.HAT1L, 0251004.MAT1L, and 0251004.NAT1L be used as direct replacements for 0251004.PAT1L in existing designs?

A: Yes. All parts share identical electrical ratings (4 A, 125 V AC/DC), response time (Fast Blow), breaking capacity (50 A AC, 300 A DC), physical dimensions (0.110" Dia x 0.280" L), and mounting type (Through Hole Axial). Substitution is electrically and mechanically valid. Packaging format differences do not affect circuit performance.

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

A: Tape & Box packaging (0251004.PAT1L) combines reel tape with a protective box, suitable for manual assembly and mixed-order quantities. Cut Tape packaging (0251004.HAT1L, 0251004.MAT1L, 0251004.NAT1L) provides components on continuous tape without box packaging, optimized for automated assembly equipment and high-volume production runs.

Q: Does REACH Affected status on 0251004.NAT1L affect its electrical performance or reliability?

A: No. REACH Affected designation indicates regulatory documentation requirements for substances of concern in specific jurisdictions. It does not alter electrical specifications, performance characteristics, or reliability. Selection should account for supply chain compliance documentation needs based on end-use location.

Q: Are all substitute parts from the same manufacturer?

A: Yes. All four part numbers are manufactured by Littelfuse Inc. and belong to the PICO® II 251 series. All parts maintain active product status with identical approval agency certifications (CCC, CSA, cURus, PSE, TUV).

Q: What are the approval agencies listed for these fuses?

A: All parts carry certifications from CCC, CSA, cURus, PSE, and TUV. These certifications confirm compliance with international safety and performance standards for board mount fuses across multiple regulatory jurisdictions.

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