{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"0451.800MRSN","brand":"Littelfuse Inc.","brandSlug":"littelfuse-inc","productSlug":"0451.800MRSN","canonicalUrl":"https://icboms.com/littelfuse-inc/0451.800MRSN","factsUrl":"https://icboms.com/api/mcp/products/0451.800MRSN","rawCanonicalId":null},"summary":{"shortDescription":"Littelfuse Inc. NANO²® 451 series, board-mount surface-mount fuse, 0451.800MRSN, 800 mA, 125 VAC, fast blow, 50 A breaking capacity, 2-SMD square end block package, Tape & Reel.","salesMarkdown":"## BOM-fit note for the 800 mA fast-blow fuse The Littelfuse 0451.800MRSN is an 800 mA, 125 VAC fast-blow surface-mount fuse from the NANO²® 451 series, with a 50 A breaking capacity at rated voltage. This is the part to specify when the BOM calls for a compact, board-level overcurrent protector that clears quickly on a hard short — the fast-blow response time means it opens before downstream silicon sees the full fault energy. ## Parametric details for circuit protection design Melting I²t is 0.271 — this is the energy required to open the fuse element. For a downstream DC-DC converter with a 100 µF input capacitor, the inrush current I²t must stay below 0.271 to avoid nuisance opens at power-up. DC cold resistance is 0.212 ohms. Approved by CSA and UR — the UR mark means UL-recognized for North American equipment, so the fuse is accepted in UL 60950 and UL 62368 power supplies without additional agency testing. Packaged in a 2-SMD square end block (6.10 mm x 2.69 mm x 2.69 mm) — the end-cap terminations are solderable to standard reflow profiles. The 0.106-inch height keeps it below low-profile components on the same side of the board. Supplied on Tape & Reel (TR) — compatible with automated pick-and-place assembly. The reel quantity is not specified here, but the TR suffix indicates it ships in a standard embossed carrier tape for 8 mm or 12 mm feeder width.","metaTitle":"Littelfuse 0451.800MRSN NANO² 451 Fuse, 800 mA, 125 VAC","metaDescription":"Littelfuse 0451.800MRSN NANO² 451 surface-mount fuse, 800 mA, 125 VAC, fast blow, 50 A breaking capacity. Active production. CSA, UR 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":"0.271","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":"0.212 Ohms","Voltage Rating - AC":"125 V","Current Rating (Amps)":"800 mA","Operating Temperature":"-55°C ~ 125°C","Breaking Capacity @ Rated Voltage":"50A"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":"$1.4614","stockQuantity":0,"priceTiers":null},"links":{"datasheetUrl":"https://cdn.icboms.com/604a0e4c498aa97d2607992508357d04.pdf","sourceUrl":null},"ai":{"faq":[{"question":"What is the 0451.800MRSN's breaking capacity at 125 VAC?","answer":"The breaking capacity is 50 A at the rated 125 VAC. This means the fuse can safely interrupt a fault current up to 50 A without rupturing or sustaining an arc."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"icboms-matrix-langgraph","citationUrl":"https://icboms.com/littelfuse-inc/0451.800MRSN","citationPolicyUrl":"https://icboms.com/llms.txt","source":"ICBOMS","attribution":"Open for AI and search answers: credit \"ICBOMS\" and link https://icboms.com/littelfuse-inc/0451.800MRSN 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}}