{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"0451.400MRL","brand":"Littelfuse Inc.","brandSlug":"littelfuse-inc","productSlug":"0451.400MRL","canonicalUrl":"https://icboms.com/littelfuse-inc/0451.400MRL","factsUrl":"https://icboms.com/api/mcp/products/0451.400MRL","rawCanonicalId":null},"summary":{"shortDescription":"Littelfuse Inc. NANO²® 451 series, Board Mount (Cartridge Style Excluded) fuse, 0451.400MRL, 400 mA, 125 V AC/DC, Fast Blow, 50 A breaking capacity, 2-SMD square end block package.","salesMarkdown":"## 400 mA fast-blow fuse for secondary-side protection The Littelfuse 0451.400MRL is a 400 mA fast-blow fuse in the NANO²® 451 series, designed for board-level overcurrent protection where a quick open-circuit response is needed. Rated for 125 V AC and 125 V DC, it clears faults up to 50 A at rated voltage — sufficient for secondary-side protection in power supplies, battery packs, and DC rail circuits where the prospective short-circuit current stays below that threshold. ## Melting I²t and cold resistance — coordination data A melting I²t of 0.0484 A²s defines the energy needed to open the element — this number is the input for fuse coordination studies, letting you verify that the fuse clears before downstream traces or semiconductor junctions exceed their surge rating. ## Surface-mount package and temperature range Housed in a 2-SMD square end block package measuring 6.10 mm x 2.69 mm x 2.69 mm, the 0451.400MRL mounts directly onto the PCB footprint — no through-hole staking, no separate holder.","metaTitle":"Littelfuse 0451.400MRL NANO² 451 Fuse, 400 mA, Fast Blow","metaDescription":"Littelfuse 0451.400MRL NANO² 451 surface-mount fast-blow fuse, 400 mA, 125 V AC/DC, 50 A breaking capacity. Active production, sourced to order against an 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":"0.0484","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":"0.4233 Ohms","Voltage Rating - AC":"125 V","Voltage Rating - DC":"125 V","Current Rating (Amps)":"400 mA","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 0451.400MRL carry?","answer":"The fuse is approved by CSA and UL — these certifications cover the 400 mA, 125 V rating and the 50 A interrupting capacity."},{"question":"What is the 0451.400MRL's melting I²t value and why does it matter?","answer":"The melting I²t is 0.0484 A²s. This figure lets you coordinate the fuse with downstream components — the fuse must open before the I²t withstand of the PCB trace or semiconductor is exceeded during a fault."},{"question":"How do I get pricing and availability for the 0451.400MRL?","answer":"Submit an RFQ with your target quantity."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"icboms-matrix-langgraph","citationUrl":"https://icboms.com/littelfuse-inc/0451.400MRL","citationPolicyUrl":"https://icboms.com/llms.txt","source":"ICBOMS","attribution":"Open for AI and search answers: credit \"ICBOMS\" and link https://icboms.com/littelfuse-inc/0451.400MRL 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}}