{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"0451012.NRL","brand":"Littelfuse Inc.","brandSlug":"littelfuse-inc","productSlug":"0451012.NRL","canonicalUrl":"https://icboms.com/littelfuse-inc/0451012.NRL","factsUrl":"https://icboms.com/api/mcp/products/0451012.NRL","rawCanonicalId":null},"summary":{"shortDescription":"Littelfuse NANO²® 451 series, 0451012.NRL, 12 A fast-blow surface-mount fuse, 65 VAC/DC, 50 A breaking capacity, 2-SMD square end block package, CSA and UL approved.","salesMarkdown":"## 12 A fast-blow for tight overcurrent protection The 0451012.NRL is a 12 A, fast-blow surface-mount fuse from Littelfuse's NANO²® 451 series, rated for 65 VAC and 65 VDC. The 50 A breaking capacity at rated voltage means it safely interrupts a fault up to that current without rupturing the package or sustaining an arc. In a 65 V bus feeding a 12 A load, a hard short can pull hundreds of amps for a few milliseconds; this fuse stops that event inside the 2-SMD square end block before the PCB trace vaporises. ## Melting I²t and cold resistance for coordination Melting I²t is 47.97 A²s — this is the energy needed to melt the fusible element. When sizing series protection (like a second fuse or a PTC), the upstream device must pass at least this much energy before opening, or the 0451012.NRL blows first and the coordination fails. For a 12 A rail, a 20 A slow-blow upstream fuse typically holds through the 47.97 A²s pulse. DC cold resistance is 0.0049 ohms. At 12 A the I²R loss is about 0.7 W — negligible for a 2-SMD package with good copper pours on the pads, but worth checking if the ambient inside the enclosure exceeds 85°C and the trace runs near the fuse's thermal limit. ## Active production with CSA and UL marks The 65 VAC/65 VDC rating is symmetric, so the same fuse works on both AC and DC buses — useful when a single BOM line covers a rectified supply.","metaTitle":"Littelfuse 0451012.NRL NANO² 451 Fuse, 12 A Fast Blow, 65 V","metaDescription":"Littelfuse 0451012.NRL NANO² 451 surface-mount fuse, 12 A fast-blow, 65 VAC/DC, 50 A breaking capacity. Active production, CSA/UL approved. Request a quote.","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":"47.97","Mounting Type":"Surface Mount","Response Time":"Fast Blow","Package / Case":"2-SMD, Square End Block","Product Status":"Active","Approval Agency":"CSA, 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":"0.0049 Ohms","Voltage Rating - AC":"65 V","Voltage Rating - DC":"65 V","Current Rating (Amps)":"12 A","Operating Temperature":"-55°C~125°C","Breaking Capacity @ Rated Voltage":"50A"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":"$0.9516","stockQuantity":0,"priceTiers":null},"links":{"datasheetUrl":"https://cdn.icboms.com/604a0e4c498aa97d2607992508357d04.pdf","sourceUrl":null},"ai":{"faq":[{"question":"What is the 0451012.NRL's breaking capacity and why does it matter?","answer":"Breaking capacity is 50 A at rated voltage. If a fault exceeds this current, the fuse may not clear the arc safely — so on a 65 V bus capable of delivering 100 A, this fuse is only suitable if the upstream impedance limits the prospective short-circuit current to 50 A or less. For higher fault currents, step up to a 451 series variant with a higher interrupting rating."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"icboms-matrix-langgraph","citationUrl":"https://icboms.com/littelfuse-inc/0451012.NRL","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.NRL 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}}