{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"0451004.NR","brand":"Littelfuse Inc.","brandSlug":"littelfuse-inc","productSlug":"0451004.NR","canonicalUrl":"https://icboms.com/littelfuse-inc/0451004.NR","factsUrl":"https://icboms.com/api/mcp/products/0451004.NR","rawCanonicalId":null},"summary":{"shortDescription":"Littelfuse NANO²® 451 series, 0451004.NR, surface-mount fast-blow fuse, 4 A, 125 V AC/DC, 50 A breaking capacity, 2-SMD square end block package, Tape & Reel.","salesMarkdown":"## What this 4 A fast-blow fuse does on your board The Littelfuse 0451004.NR is a 4 A surface-mount fuse from the NANO² 451 series, designed to clear quickly on overcurrent faults in low-voltage DC and AC circuits up to 125 V. Its fast-blow response means it opens within milliseconds on a high-magnitude fault — useful for protecting sensitive semiconductor loads where a slow-blow fuse would let through enough energy to damage downstream components. Rated 50 A breaking capacity at 125 V, it safely interrupts a fault current up to that level without rupturing the package. ## Obsolete — sourcing through independent channels No official successor order code is recorded from Littelfuse for this NANO² 451 series part. A board-level redesign using a current-production surface-mount fuse from the same family may be the practical migration path. ## Package, approvals, and thermal fit Housed in a 2-SMD square end block package measuring 6.10 mm x 2.69 mm x 2.69 mm, it reflows on a standard surface-mount line and mates with common fuse-holder pads for the NANO² footprint. Approved by CSA, PSE, and UL — the UL listing covers North American branch-circuit and supplementary protection applications; PSE acceptance allows use in equipment exported to Japan. ## Melting I²t and coordination With a melting I²t of 3.152, this fuse lets through a predictable energy pulse before opening — useful for coordinating with downstream components that have a known surge-withstand rating. The 0.016 Ohm cold DC resistance means the voltage drop at rated current is about 64 mV — negligible in a 5 V or 12 V rail, but worth checking in a 3.3 V low-dropout supply where every millivolt of headroom matters.","metaTitle":"0451004.NR Littelfuse NANO² 451 Fuse, 4 A, 125 V, Fast Blow","metaDescription":"Littelfuse 0451004.NR NANO² 451 surface-mount fast-blow fuse, 4 A, 125 V AC/DC, 50 A breaking capacity. Obsolete — sourced to order against RFQ.","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":"3.152","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":"0.016 Ohms","Voltage Rating - AC":"125 V","Voltage Rating - DC":"125 V","Current Rating (Amps)":"4 A","Operating Temperature":"-55°C ~ 125°C","Breaking Capacity @ Rated Voltage":"50A"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":"$0.5926","stockQuantity":0,"priceTiers":null},"links":{"datasheetUrl":"https://cdn.icboms.com/2e33e7b2503f3f5110226be89402b64a.pdf","sourceUrl":null},"ai":{"faq":[{"question":"What approvals does 0451004.NR carry?","answer":"It is approved by CSA, PSE, and UL. The UL listing covers North American supplementary protection; PSE acceptance covers Japan."},{"question":"What is the breaking capacity of 0451004.NR?","answer":"50 A at the rated 125 V AC/DC. This means the fuse can safely interrupt a fault current up to 50 A without rupturing."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"icboms-matrix-langgraph","citationUrl":"https://icboms.com/littelfuse-inc/0451004.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/0451004.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}}