Littelfuse 045102.5MR Surface Mount Board Mount Fuse Equivalent & Substitute Parts

Part Overview

The Littelfuse 045102.5MR is a 2.5 A, 125 V AC/DC surface mount board mount fuse in the NANO²® 451 series. This component is classified as obsolete, necessitating identification of active equivalent alternatives for new designs and ongoing production requirements. The part operates within the fast-blow response category and is housed in a 2-SMD square end block package measuring 6.10mm × 2.69mm × 2.69mm.

Substiute Parts

045102.5MR

Littelfuse Inc.In Stock: 1663045102.5MR Datasheet

Current PartRFQ

045102.5MRL

Littelfuse Inc.In Stock: 50352045102.5MRL Datasheet

DirectRFQ

044802.5MR

Littelfuse Inc.In Stock: 1597044802.5MR Datasheet

Parametric EquivalentRFQ

045102.5NRL

Littelfuse Inc.In Stock: 9657045102.5NRL Datasheet

Parametric EquivalentRFQ

045302.5MR

Littelfuse Inc.In Stock: 7474045302.5MR Datasheet

Parametric EquivalentRFQ

045302.5NR

Littelfuse Inc.In Stock: 1154045302.5NR Datasheet

Parametric EquivalentRFQ

SF-2410FP250T-2

Bourns Inc.In Stock: 935SF-2410FP250T-2 Datasheet

DirectRFQ

SF-2410HI250T-2

Bourns Inc.In Stock: 2563SF-2410HI250T-2 Datasheet

DirectRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the 045102.5MR is determined by strict equivalence across the following electrical and mechanical parameters:

• Current Rating: 2.5 A (exact match required)
• Voltage Rating: 125 V AC and 125 V DC (exact match required)
• Response Time: Fast Blow (exact match required)
• Package / Case: 2-SMD, Square End Block (exact match required)
• Mounting Type: Surface Mount (exact match required)
• Fuse Type: Board Mount (Cartridge Style Excluded) (exact match required)
• Breaking Capacity @ Rated Voltage: 50 A (exact match required)
• Operating Temperature Range: -55°C to 125°C (exact match required)

All substitute parts listed below meet these criteria. Variations in melting I²t, DC cold resistance, and series designation do not preclude substitution when all primary electrical and mechanical parameters align.

Parameter Comparison

Engineering Selection Recommendations

The 045102.5MR is obsolete and must be replaced in new designs and production. The following active alternatives are available:

Littelfuse NANO²® Series (Direct Manufacturer Alternatives):

• 045102.5MRL and 045102.5NRL are identical electrical and mechanical equivalents within the same NANO²® 451 series, both active and ROHS3 compliant. These represent the most direct replacement path.
• 044802.5MR (NANO²® 448 series) and 045302.5MR / 045302.5NR (NANO²® 453 series) are parametrically equivalent alternatives from Littelfuse, all active and ROHS3 compliant. Melting I²t values differ slightly but remain within acceptable substitution parameters.

Bourns SinglFuse™ Series (Cross-Manufacturer Alternatives):

• SF-2410FP250T-2 and SF-2410HI250T-2 are active cross-manufacturer equivalents from Bourns Inc., both ROHS3 compliant and UL/cUL certified. Physical dimensions differ slightly (0.102" width and height versus 0.106"), and melting I²t characteristics vary. SF-2410HI250T-2 exhibits significantly higher melting I²t (16.771 versus 1.029), indicating different thermal response characteristics.

All substitute parts carry CSA, PSE, and UL certifications or equivalent (cUL, UL for Bourns). Selection should prioritize active, ROHS3-compliant parts from the Littelfuse NANO²® series for design continuity, or Bourns alternatives where cross-manufacturer qualification is acceptable.

Frequently Asked Questions (FAQ)

Q: Can I use 045102.5MRL as a direct replacement for the obsolete 045102.5MR? A: Yes. The 045102.5MRL is electrically and mechanically identical to the 045102.5MR, differing only in packaging format (Tape & Reel) and product status (Active). It meets all electrical specifications and is ROHS3 compliant.

Q: What is the difference between the Littelfuse NANO²® series variants (451, 448, 453)? A: All three series (NANO²® 451, 448, and 453) meet the electrical and mechanical substitution criteria for the 045102.5MR. The series designation reflects internal design iterations. Melting I²t values are equivalent for 451 and 453 series (1.029), while the 448 series exhibits slightly higher melting I²t (1.156). All are active and ROHS3 compliant.

Q: Can I substitute a Bourns SF-2410 fuse for the Littelfuse 045102.5MR? A: Yes, parametrically. Both SF-2410FP250T-2 and SF-2410HI250T-2 meet the core electrical and mechanical requirements (2.5 A, 125 V AC/DC, fast-blow, 50 A breaking capacity, 2-SMD package). However, physical dimensions differ slightly (0.102" versus 0.106" width/height), and melting I²t characteristics vary significantly, particularly for the SF-2410HI250T-2 variant. Verify PCB layout compatibility and thermal response requirements before selection.

Q: What does "fast-blow" response time mean? A: Fast-blow fuses interrupt circuit current rapidly when rated current is exceeded, typically within milliseconds. All substitute parts listed maintain this response characteristic, ensuring consistent circuit protection behavior.

Q: Are all substitute parts RoHS compliant? A: All active substitute parts listed are ROHS3 compliant. The original 045102.5MR is RoHS non-compliant, making transition to compliant alternatives necessary for new designs and regulatory compliance.

Q: What is the significance of the melting I²t parameter? A: Melting I²t defines the thermal energy required to melt the fuse element. While substitute parts exhibit variations in this parameter, all listed alternatives remain within acceptable substitution boundaries for the 2.5 A, 125 V application. Verify application-specific thermal requirements if precise I²t matching is critical.

Q: Does packaging format (Tape & Reel versus bulk) affect electrical performance? A: No. Packaging format affects only handling, storage, and assembly logistics. Electrical and mechanical performance remain identical regardless of packaging configuration.