{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"0451004.MRL","brand":"Littelfuse Inc.","brandSlug":"littelfuse-inc","productSlug":"0451004.MRL","canonicalUrl":"https://icboms.com/littelfuse-inc/0451004.MRL","factsUrl":"https://icboms.com/api/mcp/products/0451004.MRL","rawCanonicalId":null},"summary":{"shortDescription":"Littelfuse NANO²® 451 series, 0451004.MRL, 4 A, 125 V AC/DC, fast-blow, surface-mount fuse, 2-SMD square end block package, Tape & Reel.","salesMarkdown":"## 4 A fast-blow SMD fuse for secondary-side protection The Littelfuse 0451004.MRL is a 4 A fast-blow surface-mount fuse from the NANO²® 451 series, rated for 125 V AC and DC circuits. 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 key parameter for secondary-side protection in power supplies and DC-DC converters where the available fault current is known. 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. The fast-blow characteristic clears overcurrent events quickly, limiting let-through energy to downstream semiconductors — the 3.152 melting I²t figure gives the board designer the data needed to coordinate with downstream traces and components. ## Approvals and temperature envelope The 0451004.MRL carries CSA, PSE, and UL approvals, covering North American and Japanese regulatory acceptance for equipment-level safety certification.","metaTitle":"0451004.MRL Littelfuse NANO² 451 4A Fast-Blow SMD Fuse","metaDescription":"0451004.MRL Littelfuse NANO² 451 series 4A fast-blow SMD fuse, 125V AC/DC, 50A breaking capacity, CSA/PSE/UL approved. 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, 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":"0.016 Ohms","Voltage Rating - AC":"125 V","Voltage Rating - DC":"125 V","Current Rating (Amps)":"4 A","Operating Temperature":"-55°C ~ 125°C","Breaking Capacity @ Rated Voltage":"50A"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":"$1.4600","stockQuantity":0,"priceTiers":null},"links":{"datasheetUrl":"https://cdn.icboms.com/2e33e7b2503f3f5110226be89402b64a.pdf","sourceUrl":null},"ai":{"faq":[{"question":"What approvals does the 0451004.MRL carry?","answer":"The fuse is approved by CSA, PSE, and UL, covering North American and Japanese safety certification for equipment-level circuit protection."},{"question":"What is the 0451004.MRL's melting I²t value?","answer":"The melting I²t is 3.152, which is used for fuse-to-trace coordination and let-through energy calculations in the board design."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"icboms-matrix-langgraph","citationUrl":"https://icboms.com/littelfuse-inc/0451004.MRL","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.MRL 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}}