Littelfuse 0665.500ZRLL Equivalent & Substitute Parts

Part Overview

The Littelfuse 0665.500ZRLL is a 500 mA, 250 V AC/DC board mount radial fuse with slow blow response characteristics, designed for through-hole mounting applications. This component is classified as obsolete, making identification of functionally equivalent alternatives essential for ongoing design support and production continuity. The TR5® 374 series substitute provides equivalent electrical performance with active product status and improved availability.

Substiute Parts

0665.500ZRLL

Littelfuse Inc.In Stock: 10370665.500ZRLL Datasheet

Current PartRFQ

37405000000

Littelfuse Inc.In Stock: 1538437405000000 Datasheet

DirectRFQ

Key Parameters

Substitute Part Grouping Explanation

The Littelfuse 37405000000 qualifies as a direct substitute for the 0665.500ZRLL based on the following critical parameters:

Current Rating: Both parts are rated at 500 mA, ensuring identical circuit protection thresholds.

Voltage Rating: Both maintain 250 V AC rating, supporting equivalent application voltage requirements.

Response Time: Both employ slow blow characteristics, providing identical inrush current tolerance and protection behavior.

Mounting Configuration: Both are through-hole mounted radial fuses with identical package style (Radial, Can, Vertical), ensuring mechanical and electrical compatibility on existing PCB layouts.

Breaking Capacity: Both are rated at 50 A @ rated voltage, maintaining equivalent fault current handling capability.

Operating Temperature: Both operate across -40°C to 85°C, supporting identical environmental specifications.

Regulatory Compliance: Both hold CSA and UL-based certifications (cULus is the Canadian/US combined certification), meeting equivalent safety standards.

Parameter Comparison

Engineering Selection Recommendations

The Littelfuse 37405000000 is the direct functional equivalent for the obsolete 0665.500ZRLL. Selection of the substitute is based on:

Product Status: The 37405000000 maintains active product status with confirmed inventory availability (15,300 pcs), whereas the 0665.500ZRLL is obsolete with limited remaining stock (937 pcs).

Regulatory Compliance: Both parts hold equivalent safety certifications. The 37405000000 carries cULus certification, which represents combined CSA and UL approval and is recognized across North American markets.

Electrical Equivalence: Identical current rating, voltage rating, response time, and breaking capacity ensure drop-in compatibility for circuit protection applications.

Physical Compatibility: Both parts share identical package geometry (Radial, Can, Vertical configuration), supporting direct PCB layout compatibility without redesign.

Environmental Specifications: Matching operating temperature ranges (-40°C to 85°C) ensure equivalent performance across industrial and commercial temperature profiles.

Frequently Asked Questions (FAQ)

Q: Can the 37405000000 be used as a direct replacement for the 0665.500ZRLL on existing PCBs?

A: Yes. Both parts are through-hole mounted radial fuses with identical package dimensions and electrical ratings. No PCB layout modifications are required.

Q: What is the difference between the packaging formats (Tape & Reel vs. Cut Tape)?

A: Tape & Reel (TR) packaging is supplied on continuous tape for automated assembly equipment. Cut Tape (CT) packaging is supplied in individual tape segments. Both formats contain the same component; the difference is in handling and assembly method. Verify your assembly process compatibility before ordering.

Q: Are the thermal and electrical characteristics identical between these parts?

A: Yes. Both parts operate across -40°C to 85°C, maintain 500 mA current rating, 250 V voltage rating, and 50 A breaking capacity. The slow blow response time is identical, ensuring equivalent inrush current tolerance.

Q: What does cULus certification mean compared to separate CSA and UL certifications?

A: cULus represents a combined certification from both CSA (Canadian Standards Association) and UL (Underwriters Laboratories). This single certification satisfies regulatory requirements for both Canadian and US markets. It is equivalent to holding both certifications separately.

Q: Are there any differences in DC cold resistance between these parts?

A: The 0665.500ZRLL has 0.243 Ohms DC cold resistance, while the 37405000000 has 0.26 Ohms. This minor difference does not affect circuit protection performance for the specified 500 mA rating and is within acceptable engineering tolerance for fuse applications.

Q: What is the melting I²t difference, and does it affect substitution?

A: The 0665.500ZRLL has 0.898 melting I²t, while the 37405000000 has 0.6 melting I²t. Both values fall within the slow blow fuse category and maintain the same response time classification. The substitute provides equivalent protection for the specified 500 mA application.

Q: Is the 37405000000 RoHS compliant?

A: Yes. The 37405000000 is ROHS3 compliant, matching the compliance status of the 0665.500ZRLL.