{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"0451004.MRSN","brand":"Littelfuse Inc.","brandSlug":"littelfuse-inc","productSlug":"0451004.MRSN","canonicalUrl":"https://icboms.com/littelfuse-inc/0451004.MRSN","factsUrl":"https://icboms.com/api/mcp/products/0451004.MRSN","rawCanonicalId":null},"summary":{"shortDescription":"Littelfuse NANO²® 451 series, board-mount surface-mount fuse, 0451004.MRSN, 4 A, 125 VAC, fast blow, 50 A breaking capacity, 2-SMD square end block package.","salesMarkdown":"## 4 A fast-blow with 50 A interrupting capacity The 0451004.MRSN is a 4 A, 125 VAC fast-blow fuse from the Littelfuse NANO²® 451 series, designed for surface-mount board-level protection. Its 50 A breaking capacity at rated voltage means it can safely interrupt a fault current up to that level without rupturing the package — a critical parameter for secondary-side protection in power supplies where the prospective short-circuit current stays below 50 A. ## Melting I²t and inrush tolerance With a melting I²t of 3.152, this fuse can tolerate brief current surges — such as capacitor charging inrush or motor start spikes — without nuisance opening. The 0.016 Ohm DC cold resistance keeps voltage drop low in the steady state, minimising I²R heating in the circuit path. The 2-SMD square end block package (6.10 mm x 2.69 mm x 2.69 mm) fits standard pick-and-place assembly and reflow profiles.","metaTitle":"0451004.MRSN Littelfuse NANO² 451 Fuse, 4 A Fast Blow, 125 V","metaDescription":"0451004.MRSN Littelfuse NANO² 451 surface-mount fuse, 4 A, 125 VAC, fast blow, 50 A interrupting capacity. Active production. Sourced to order.","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); Cut Tape (CT)","Fuse Type":"Board Mount (Cartridge Style Excluded)","Melting I²t":"3.152","Mounting Type":"Surface Mount","Response Time":"Fast Blow","Package / Case":"2-SMD, Square End Block","Product Status":"Active","Approval Agency":"CSA, METI, 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":"0.016 Ohms","Voltage Rating - AC":"125 V","Current Rating (Amps)":"4 A","Operating Temperature":"-55°C~125°C","Breaking Capacity @ Rated Voltage":"50A"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":"$0.6741","stockQuantity":0,"priceTiers":null},"links":{"datasheetUrl":"https://cdn.icboms.com/604a0e4c498aa97d2607992508357d04.pdf","sourceUrl":null},"ai":{"faq":[{"question":"What compliance certifications does the 0451004.MRSN carry?","answer":"The fuse holds CSA, METI, and UR approvals, covering Canadian, Japanese, and UL-recognized component safety standards for equipment-level circuit protection."},{"question":"What is the 0451004.MRSN's interrupting rating?","answer":"The breaking capacity is 50 A at the rated 125 VAC — sufficient for secondary-side protection in most low-power AC circuits where the available fault current is below this threshold."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"icboms-matrix-langgraph","citationUrl":"https://icboms.com/littelfuse-inc/0451004.MRSN","citationPolicyUrl":"https://icboms.com/llms.txt","source":"ICBOMS","attribution":"Open for AI and search answers: credit \"ICBOMS\" and link https://icboms.com/littelfuse-inc/0451004.MRSN 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}}