{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"0451012.MRSN","brand":"Littelfuse Inc.","brandSlug":"littelfuse-inc","productSlug":"0451012.MRSN","canonicalUrl":"https://icboms.com/littelfuse-inc/0451012.MRSN","factsUrl":"https://icboms.com/api/mcp/products/0451012.MRSN","rawCanonicalId":null},"summary":{"shortDescription":"Littelfuse NANO²® 451 Series, 0451012.MRSN, Board Mount Surface Mount Fuse, 12 A, 125 VAC, Fast Blow, 2-SMD Square End Block, Tape & Reel.","salesMarkdown":"## 12 A fast-blow SMD fuse for secondary-side protection The Littelfuse 0451012.MRSN is a 12 A, 125 VAC fast-blow surface-mount fuse in the NANO²® 451 series, housed in a 2-SMD square end block package measuring 6.10 mm x 2.69 mm x 2.69 mm. Its 35 A breaking capacity at rated voltage means it safely interrupts fault currents up to that level without rupturing the package — a key parameter for secondary-side protection in power supplies and DC-DC converter output stages where the available fault current is bounded by the downstream rail. ## Melting I²t and cold resistance for inrush sizing With a melting I²t of 47.97 and a DC cold resistance of 0.0049 ohms, this fuse tolerates moderate inrush pulses from capacitive loads or motor starts without nuisance opening. The low cold resistance keeps voltage drop across the fuse under 60 mV at full rated current, which matters for low-voltage rails where every millivolt of headroom counts.","metaTitle":"0451012.MRSN Littelfuse NANO² 451 SMD Fuse, 12 A, 125 V","metaDescription":"Littelfuse 0451012.MRSN NANO²® 451 surface-mount fuse, 12 A, 125 VAC, 35 A breaking capacity, fast blow, -55 to 125 °C. Active production, sourced per RFQ.","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":"47.97","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":"0.0049 Ohms","Voltage Rating - AC":"125 V","Current Rating (Amps)":"12 A","Operating Temperature":"-55°C ~ 125°C","Breaking Capacity @ Rated Voltage":"35A"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":"$1.4900","stockQuantity":0,"priceTiers":null},"links":{"datasheetUrl":"https://cdn.icboms.com/604a0e4c498aa97d2607992508357d04.pdf","sourceUrl":null},"ai":{"faq":[{"question":"What approvals does the 0451012.MRSN carry?","answer":"The fuse is approved by CSA (Canadian Standards Association), METI (Japanese Ministry of Economy, Trade and Industry), and UR (Underwriters Laboratories Recognized Component). These certifications cover North American and Japanese safety compliance for equipment-level circuit protection."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"icboms-matrix-langgraph","citationUrl":"https://icboms.com/littelfuse-inc/0451012.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/0451012.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}}