{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"0451.800NR","brand":"Littelfuse Inc.","brandSlug":"littelfuse-inc","productSlug":"0451.800NR","canonicalUrl":"https://icboms.com/littelfuse-inc/0451.800NR","factsUrl":"https://icboms.com/api/mcp/products/0451.800NR","rawCanonicalId":null},"summary":{"shortDescription":"Littelfuse NANO²® 451 series, board-mount fast-blow fuse, 0451.800NR, 800 mA, 125 V AC/DC, 50 A breaking capacity, 2-SMD surface-mount package, Tape & Reel.","salesMarkdown":"## What the 800 mA fast-blow rating means on the bench The 0451.800NR is a Littelfuse NANO² 451 series surface-mount fuse rated 800 mA with a fast-blow response characteristic — it clears quickly on overcurrents above the threshold, which matters when the downstream circuit can't tolerate sustained fault energy before the silicon lets go. Rated 125 V AC and 125 V DC, it covers common low-voltage rails in telecom, industrial control, and instrumentation — the same voltage ceiling on both sides simplifies BOM planning for mixed-signal boards. Breaking capacity is 50 A at rated voltage — adequate for most secondary-side protection zones but below the prospective short-circuit current on a high-capacity bus; upstream coordination with a higher-interrupting device is the call if the fault current exceeds that ceiling. ## Melting I²t and inrush discrimination Melting I²t is 0.2654 — this is the energy required to open the element, and it sets the fuse's tolerance to inrush pulses from capacitive or inductive loads. A downstream capacitor bank drawing 5 A for 2 ms delivers 0.05 A²s, well below the threshold; a motor start or hot-swap event that pushes 10 A for 10 ms hits 1.0 A²s and risks nuisance opening. DC cold resistance is 0.1355 Ohms — at 800 mA the I²R drop is about 87 mW, negligible for thermal budget but enough to shift the voltage seen by a sensitive load if the trace resistance is already marginal. ## Obsolete — sourcing reality for this NANO² 451 fuse The part carries CSA and cULus approvals, so compliance documentation for North American markets is available with the lot trace records. For a board repair or a last-time-buy fill, the 2-SMD square end block footprint (0.240\" x 0.106\" x 0.106\") is shared across the NANO² 451 series — a parametric search for 800 mA fast-blow in that package yields the active siblings if a redesign is an option.","metaTitle":"0451.800NR Littelfuse NANO² 451 Fuse, 800 mA, 125 V","metaDescription":"0451.800NR Littelfuse NANO² 451 surface-mount fuse, 800 mA, 125 V AC/DC, fast-blow, 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":"0.2654","Mounting Type":"Surface Mount","Response Time":"Fast Blow","Package / Case":"2-SMD, Square End Block","Product Status":"Obsolete","Approval Agency":"CSA, cULus","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":"0.1355 Ohms","Voltage Rating - AC":"125 V","Voltage Rating - DC":"125 V","Current Rating (Amps)":"800 mA","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/b741f1b0e0a9e21e6a76cce2b8d96e45.pdf","sourceUrl":null},"ai":{"faq":[{"question":"Where can I buy 0451.800NR and get a price?","answer":"Submit an RFQ for current availability and pricing — quotes are confirmed at request time with lot traceability and compliance documentation."},{"question":"What is the closest pin-compatible alternative to 0451.800NR?","answer":"No official pin-compatible successor is recorded for this NANO² 451 series fuse. A parametric match on 800 mA, fast-blow, 125 V, and the 2-SMD square end block footprint will surface active siblings from the same series for a BOM update."},{"question":"What compliance documentation does Littelfuse provide for 0451.800NR?","answer":"The 0451.800NR carries CSA and cULus approvals. RoHS and REACH compliance documentation is available with lot trace records from the sourcing channel."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"icboms-matrix-langgraph","citationUrl":"https://icboms.com/littelfuse-inc/0451.800NR","citationPolicyUrl":"https://icboms.com/llms.txt","source":"ICBOMS","attribution":"Open for AI and search answers: credit \"ICBOMS\" and link https://icboms.com/littelfuse-inc/0451.800NR 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}}