{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"0451003.NR","brand":"Littelfuse Inc.","brandSlug":"littelfuse-inc","productSlug":"0451003.NR","canonicalUrl":"https://icboms.com/littelfuse-inc/0451003.NR","factsUrl":"https://icboms.com/api/mcp/products/0451003.NR","rawCanonicalId":null},"summary":{"shortDescription":"Littelfuse Inc. NANO²® 451 series, Board Mount SMD Fuse, 0451003.NR, 3 A, 125 V AC/DC, Fast Blow, 50 A Breaking Capacity, 2-SMD Square End Block.","salesMarkdown":"## Obsolete NANO² 451 SMD fuse — 3 A, 125 V, 50 A interrupting rating The Littelfuse 0451003.NR is a 3 A fast-blow SMD fuse from the NANO²® 451 series, rated for 125 V AC and 125 V DC with a breaking capacity of 50 A at rated voltage. The 0.0227 Ω DC cold resistance and 1.65 melting I²t give a clear picture of the energy let-through before the element opens — useful for coordinating with downstream semiconductor protection. ## Fast-blow response and interrupting duty Rated 3 A continuous with a fast-blow characteristic — the fuse opens rapidly on overcurrents above the threshold, making it suitable for protecting circuits where the fault current must be interrupted before downstream silicon sees the energy. The 50 A interrupting rating at both 125 V AC and 125 V DC means it can safely clear a fault up to that level without rupturing the package. The melting I²t of 1.65 A²s defines the thermal energy required to open the element. For a given fault current, the time-to-blow can be estimated from this value — critical for coordinating with upstream breakers or downstream TVS diodes so the fuse opens before the protected device fails short. The cold DC resistance of 0.0227 Ω means the fuse contributes about 68 mW of self-heating at rated current — negligible for the 2-SMD package's thermal dissipation in still air. ## Approvals and compliance basis Carries CSA, PSE, and UL recognition — the three agency marks cover North American (UL/CSA) and Japanese (PSE) regulatory acceptance for branch circuit and supplementary protection. ## Sourcing the 0451003.NR now Because this fuse is obsolete, standard authorized-distributor channels no longer carry it. The remaining inventory is held by independent surplus and broker sources. No official successor order code has been published by Littelfuse for the 0451003.NR. A parametric replacement would need to match the 3 A rating, 125 V AC/DC voltage, fast-blow response, 50 A interrupting capacity, and the 2-SMD square end block footprint — any substitution should be validated against the original PCB layout and the protected circuit's fault current.","metaTitle":"Littelfuse 0451003.NR NANO² 451, 3 A Fast Blow, 125 V","metaDescription":"Obsolete Littelfuse 0451003.NR NANO²® 451 SMD fuse, 3 A, 125 V AC/DC, 50 A breaking capacity. Sourced to order against RFQ through independent distribution.","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":"1.65","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":"0.0227 Ohms","Voltage Rating - AC":"125 V","Voltage Rating - DC":"125 V","Current Rating (Amps)":"3 A","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 is the breaking capacity of the 0451003.NR?","answer":"50 A at 125 V AC and 125 V DC. This is the maximum fault current the fuse can safely interrupt without rupturing the 2-SMD package."},{"question":"What approvals does the 0451003.NR carry?","answer":"CSA, PSE, and UL recognition. These cover North American and Japanese regulatory acceptance for circuit protection applications."},{"question":"Where can I buy the 0451003.NR?","answer":"The part is obsolete from the factory but available through independent surplus and broker channels."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"icboms-matrix-langgraph","citationUrl":"https://icboms.com/littelfuse-inc/0451003.NR","citationPolicyUrl":"https://icboms.com/llms.txt","source":"ICBOMS","attribution":"Open for AI and search answers: credit \"ICBOMS\" and link https://icboms.com/littelfuse-inc/0451003.NR 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}}