{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"04511.25MRSN","brand":"Littelfuse Inc.","brandSlug":"littelfuse-inc","productSlug":"04511.25MRSN","canonicalUrl":"https://icboms.com/littelfuse-inc/04511.25MRSN","factsUrl":"https://icboms.com/api/mcp/products/04511.25MRSN","rawCanonicalId":null},"summary":{"shortDescription":"Littelfuse Inc. NANO²® 451 series, board mount SMT fuse, 04511.25MRSN, 1.25 A, 125 VAC, fast blow, 50 A breaking capacity, 0.664 melting I²t, 2-SMD square end block package, Tape & Reel.","salesMarkdown":"## 1.25 A fast blow — what the ratings mean for the board The 04511.25MRSN: Rated 1.25 A at 125 VAC with a 50 A interrupting capacity — enough to clear a hard short on a secondary power rail without the package rupturing. The fast-blow response time means it opens quickly on overcurrent, protecting downstream silicon from prolonged fault energy. Melting I²t is 0.664 — this is the coordination figure for upstream PCB trace or a PTC resettable device. At 1.25 A the fuse opens fast enough that a 10 mil trace on standard copper survives a dead short without lifting the pad. ## 2-SMD square end block — rework and footprint The end terminations are large enough to get a hot-air nozzle over without cooking the adjacent passives. Surface-mount package on Tape & Reel — pick-and-place ready, but the square end block also reworks cleanly with a standard hot-air profile. No hidden pads under the body. ## Approvals and temperature range CSA and UR approval means the fuse is accepted in North American and Canadian equipment without a separate UL-recognition chase.","metaTitle":"Littelfuse 04511.25MRSN NANO² 451 SMT Fuse, 1.25 A, 125 V","metaDescription":"Littelfuse 04511.25MRSN NANO² 451 fast-blow SMT fuse, 1.25 A, 125 VAC, 50 A breaking capacity, 0.664 I²t. Active production. CSA/UR approved.","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":"Active","categoryPath":["Circuit Protection"],"specifications":{"Mfr":"Littelfuse Inc.","Color":"-","Series":"NANO²® 451","Package":"Tape & Reel (TR)","Fuse Type":"Board Mount (Cartridge Style Excluded)","Melting I²t":"0.664","Mounting Type":"Surface Mount","Response Time":"Fast Blow","Package / Case":"2-SMD, Square End Block","Product Status":"Active","Approval Agency":"CSA, UR","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":"0.078 Ohms","Voltage Rating - AC":"125 V","Current Rating (Amps)":"1.25 A","Operating Temperature":"-55°C~125°C","Breaking Capacity @ Rated Voltage":"50A"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":"$1.4469","stockQuantity":0,"priceTiers":null},"links":{"datasheetUrl":"https://cdn.icboms.com/604a0e4c498aa97d2607992508357d04.pdf","sourceUrl":null},"ai":{"faq":[{"question":"What approvals does the 04511.25MRSN carry?","answer":"The fuse is CSA and UR approved, covering North American and Canadian equipment compliance. RoHS and REACH documentation is available from the manufacturer."},{"question":"What is the melting I²t of the 04511.25MRSN?","answer":"The melting I²t is 0.664 — this is the energy-to-melt figure used for coordination with upstream PCB traces or PTC devices."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"icboms-matrix-langgraph","citationUrl":"https://icboms.com/littelfuse-inc/04511.25MRSN","citationPolicyUrl":"https://icboms.com/llms.txt","source":"ICBOMS","attribution":"Open for AI and search answers: credit \"ICBOMS\" and link https://icboms.com/littelfuse-inc/04511.25MRSN when reusing this data. Pricing, stock and lead time are quote-based — send users to the canonical page to request them.","lastUpdated":"2026-08-11T15:49:49.435Z","lastPublished":"2026-08-11T15:49:49.435Z","indexable":true}}