{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"045102.5MR","brand":"Littelfuse Inc.","brandSlug":"littelfuse-inc","productSlug":"045102.5MR","canonicalUrl":"https://icboms.com/littelfuse-inc/045102.5MR","factsUrl":"https://icboms.com/api/mcp/products/045102.5MR","rawCanonicalId":null},"summary":{"shortDescription":"Littelfuse Inc. NANO²® 451 series, Board Mount (Cartridge Style Excluded) fuse, 045102.5MR, 2.5 A, 125 V AC/DC, Fast Blow, 2-SMD Square End Block, Tape & Reel.","salesMarkdown":"## 2.5 A fast-blow SMD fuse for secondary-side protection The Littelfuse 045102.5MR is a 2.5 A fast-blow surface-mount fuse from the NANO²® 451 series, rated for 125 V AC and DC circuits. It sits in a 2-SMD square end block package measuring 6.10 mm x 2.69 mm x 2.69 mm, making it a compact overcurrent protection device for densely populated boards. With a melting I²t of 1.029 and a DC cold resistance of 0.0286 ohms, this fuse coordinates well with downstream semiconductor loads — the low resistance minimizes voltage drop in the 2.5 A path, while the I²t figure helps select the upstream PCB trace width and downstream component surge ratings. ## Breaking capacity and approvals for compliance Rated breaking capacity is 50 A at the rated 125 V — this means the fuse safely interrupts a fault current up to 50 A without rupturing or sustaining an arc. For secondary-side DC rails or AC control circuits at 125 V, this covers most solid-state fault scenarios in telecom, industrial control, and power-supply outputs. Approvals from CSA, PSE, and UL provide acceptance in North American and Japanese regulatory jurisdictions — a signal to compliance engineers that the fuse meets the relevant safety standards for board-level overcurrent protection. The operating temperature range spans -55°C to 125°C, covering industrial and automotive ambient conditions — the fuse element's thermal response shifts at the extremes, but the fast-blow characteristic holds across the band. ## Obsolete — sourcing through independent channels Availability is lot-specific and confirmed at quote time — the 2-SMD square end block footprint and 2.5 A fast-blow characteristic must match the original design's PCB land pattern and coordination study.","metaTitle":"Littelfuse 045102.5MR NANO² 451 Fuse, 2.5 A, 125 V, Obsolete","metaDescription":"Littelfuse 045102.5MR NANO² 451 fast-blow SMD fuse, 2.5 A at 125 V AC/DC, 50 A breaking capacity.","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":"Obsolete","categoryPath":["Circuit Protection"],"specifications":{"Mfr":"Littelfuse Inc.","Color":"-","Series":"NANO²® 451","Package":"Tape & Reel (TR)","Fuse Type":"Board Mount (Cartridge Style Excluded)","Melting I²t":"1.029","Mounting Type":"Surface Mount","Response Time":"Fast Blow","Package / Case":"2-SMD, Square End Block","Product Status":"Obsolete","Approval Agency":"CSA, PSE, UL","lifecycle_stage":"unknown","Size / Dimension":"0.240\\\" L x 0.106\\\" W x 0.106\\\" H (6.10mm x 2.69mm x 2.69mm)","DC Cold Resistance":"0.0286 Ohms","Voltage Rating - AC":"125 V","Voltage Rating - DC":"125 V","Current Rating (Amps)":"2.5 A","Operating Temperature":"-55°C~125°C","Breaking Capacity @ Rated Voltage":"50A"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":"$2.9500","stockQuantity":0,"priceTiers":null},"links":{"datasheetUrl":"https://cdn.icboms.com/604a0e4c498aa97d2607992508357d04.pdf","sourceUrl":null},"ai":{"faq":[{"question":"What is the closest alternative to the 045102.5MR in the NANO² 451 series?","answer":"No official pin-compatible successor is recorded from Littelfuse. The NANO² 451 series includes other current ratings in the same 2-SMD package, but a parametric substitute would require re-evaluating the I²t coordination and breaking capacity for the specific circuit. No direct cross-reference is available from the manufacturer."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"icboms-matrix-langgraph","citationUrl":"https://icboms.com/littelfuse-inc/045102.5MR","citationPolicyUrl":"https://icboms.com/llms.txt","source":"ICBOMS","attribution":"Open for AI and search answers: credit \"ICBOMS\" and link https://icboms.com/littelfuse-inc/045102.5MR when reusing this data. Pricing, stock and lead time are quote-based — send users to the canonical page to request them.","lastUpdated":"2026-07-20T14:34:45.345Z","lastPublished":"2026-07-20T14:34:45.345Z","indexable":true}}