Littelfuse 0665002.ZRLL Board Mount Fuse Equivalent & Substitute Parts

Part Overview

The Littelfuse 0665002.ZRLL is a 2 A, 250 V AC/DC board mount fuse with slow blow response characteristics, designed for through-hole radial mounting in the LT-5™ 665 series. This component is classified as obsolete, making identification of functionally equivalent alternatives necessary for ongoing design support and procurement planning. The part features a radial, can-style vertical package with a breaking capacity of 50 A at rated voltage and operates across a temperature range of -40°C to 85°C.

Substiute Parts

0665002.ZRLL

LittelfuseIn Stock: 8170665002.ZRLL Datasheet

Current PartRFQ

37412000000

Littelfuse Inc.In Stock: 233437412000000 Datasheet

DirectRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for the 0665002.ZRLL is determined by strict equivalence across the following critical parameters:

• Current Rating: 2 A (exact match required)
• Voltage Rating (AC): 250 V (exact match required)
• Response Time: Slow Blow (exact match required)
• Mounting Type: Through Hole (exact match required)
• Fuse Type: Board Mount, Cartridge Style Excluded (exact match required)
• Package / Case: Radial, Can, Vertical (exact match required)
• Breaking Capacity @ Rated Voltage: 50 A (exact match required)
• Operating Temperature Range: -40°C to 85°C (exact match required)
• Regulatory Compliance: CSA and UL approval (minimum requirement)

The substitute part 37412000000 meets all critical electrical and mechanical parameters. Variations in melting I²t, DC cold resistance, and physical dimensions (height) are within acceptable tolerances for board mount fuse applications and do not affect functional interchangeability in the specified circuit application.

Parameter Comparison

Engineering Selection Recommendations

The Littelfuse 37412000000 is the direct functional equivalent for the obsolete 0665002.ZRLL. Selection of this substitute is supported by:

• Active product status ensuring long-term availability and supply chain continuity
• Identical electrical ratings (2 A, 250 V AC/DC, 50 A breaking capacity)
• Matching slow blow response characteristics and operating temperature range
• Equivalent regulatory certifications (CSA, cULus) meeting or exceeding original approval requirements
• ROHS3 compliance alignment with environmental standards
• Through-hole radial mounting compatibility with existing PCB layouts

The minor height reduction (0.333" to 0.315") and variation in melting I²t and DC cold resistance do not compromise functional performance in board mount fuse applications where these parameters remain within acceptable design tolerances.

Frequently Asked Questions (FAQ)

Q: Can the 37412000000 be used as a direct replacement for the 0665002.ZRLL without PCB modification?

A: Yes. Both parts share identical current rating (2 A), voltage rating (250 V AC), response time (slow blow), mounting type (through hole), and package configuration (radial, can, vertical). The 0.018" height difference does not require PCB redesign for standard board mount applications.

Q: What is the significance of the different melting I²t values (28.6 vs. 7.5)?

A: Melting I²t defines the thermal energy required to melt the fuse element. The lower value in the 37412000000 indicates faster thermal response under fault conditions, which is acceptable for slow blow fuses and does not affect compatibility in the specified application.

Q: Are the regulatory certifications equivalent between the two parts?

A: Both parts carry CSA approval. The 0665002.ZRLL holds UL certification, while the 37412000000 holds cULus certification. The cULus mark indicates CSA and UL joint certification, meeting or exceeding the original approval requirements.

Q: Does the DC cold resistance difference (0.034 vs. 0.0395 Ohms) affect circuit performance?

A: The resistance variation is within acceptable tolerances for board mount fuse applications and does not materially affect circuit operation or thermal performance in standard designs.

Q: Why is the 0665002.ZRLL classified as obsolete?

A: Obsolete status indicates the part is no longer manufactured. The 37412000000 from the active TR5® 374 series provides equivalent functionality with current manufacturing support and availability.