{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"04511.25MR","brand":"Littelfuse Inc.","brandSlug":"littelfuse-inc","productSlug":"04511.25MR","canonicalUrl":"https://icboms.com/littelfuse-inc/04511.25MR","factsUrl":"https://icboms.com/api/mcp/products/04511.25MR","rawCanonicalId":null},"summary":{"shortDescription":"Littelfuse Inc. NANO²® 451 series fast-blow surface-mount fuse, 04511.25MR, 1.25 A, 125 V AC/DC, 50 A breaking capacity, 2-SMD square end block package, Tape & Reel.","salesMarkdown":"## Fast-blow SMT fuse, now in surplus channel The Littelfuse 04511.25MR is a 1.25 A fast-blow surface-mount fuse from the NANO² 451 series, rated for 125 V AC and DC with a breaking capacity of 50 A at rated voltage. lists this part as obsolete, meaning original factory production has ceased; supply now runs through independent surplus and broker channels, with quantities and pricing confirmed per RFQ. ## Parametric fit and board-level considerations Melting I²t is 0.664 — this value governs the fuse's ability to withstand inrush currents without nuisance opening; a downstream capacitor bank or motor start with a surge exceeding this I²t threshold will blow the fuse on power-up. DC cold resistance measures 0.078 Ω, which at 1.25 A produces roughly 0.12 W of self-heating — negligible in still air but relevant when the fuse is packed inside a sealed module with no convection path. Package is a 2-SMD square end block measuring 6.10 mm x 2.69 mm x 2.69 mm — the ceramic body and end-cap construction are designed for the 50 A interrupting rating; a standard 1206 or 2410 footprint will not match this form factor. Approved by CSA, PSE, and UL — the UL listing is the one most North American safety reviewers will look for; the PSE mark covers Japanese market compliance. ## Obsolete — sourcing this fuse today Available through independent distribution; lot traceability and manufacturer date codes are confirmed at the time of RFQ. No pin-compatible drop-in replacement from Littelfuse is documented, so a BOM-line substitution requires verifying the same package footprint and I²t characteristic.","metaTitle":"Littelfuse 04511.25MR NANO² 451 Fuse, 1.25A, 125V, Fast Blow","metaDescription":"Littelfuse 04511.25MR NANO² 451 series fast-blow surface-mount fuse, 1.25A, 125V AC/DC, 50A breaking capacity.","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":"Obsolete","categoryPath":["Circuit Protection"],"specifications":{"Mfr":"Littelfuse Inc.","Color":"-","Series":"NANO²® 451","Package":"Tape & Reel (TR)","Fuse Type":"Board Mount (Cartridge Style Excluded)","Melting I²t":"0.664","Mounting Type":"Surface Mount","Response Time":"Fast Blow","Package / Case":"2-SMD, Square End Block","Product Status":"Obsolete","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":"0.078 Ohms","Voltage Rating - AC":"125 V","Voltage Rating - DC":"125 V","Current Rating (Amps)":"1.25 A","Operating Temperature":"-55°C ~ 125°C","Breaking Capacity @ Rated Voltage":"50A"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":"$1.5300","stockQuantity":0,"priceTiers":null},"links":{"datasheetUrl":"https://cdn.icboms.com/2e33e7b2503f3f5110226be89402b64a.pdf","sourceUrl":null},"ai":{"faq":[{"question":"How do I get current pricing and availability for 04511.25MR?","answer":"Submit an RFQ against your BOM quantity."},{"question":"What approvals does 04511.25MR carry?","answer":"CSA, PSE, and UL approvals are listed on the fuse. The UL mark satisfies North American safety agency requirements; PSE covers Japanese regulatory compliance."},{"question":"What is the melting I²t and why does it matter?","answer":"Melting I²t is 0.664. This number is the thermal energy required to open the fuse element. If the inrush current pulse from a capacitive load or motor start exceeds this I²t, the fuse will blow during turn-on rather than protecting against a sustained fault."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"icboms-matrix-langgraph","citationUrl":"https://icboms.com/littelfuse-inc/04511.25MR","citationPolicyUrl":"https://icboms.com/llms.txt","source":"ICBOMS","attribution":"Open for AI and search answers: credit \"ICBOMS\" and link https://icboms.com/littelfuse-inc/04511.25MR when reusing this data. Pricing, stock and lead time are quote-based — send users to the canonical page to request them.","lastUpdated":"2026-07-20T14:34:45.345Z","lastPublished":"2026-07-20T14:34:45.345Z","indexable":true}}