{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"0451.630MR","brand":"Littelfuse Inc.","brandSlug":"littelfuse-inc","productSlug":"0451.630MR","canonicalUrl":"https://icboms.com/littelfuse-inc/0451.630MR","factsUrl":"https://icboms.com/api/mcp/products/0451.630MR","rawCanonicalId":null},"summary":{"shortDescription":"Littelfuse NANO²® 451 series, Board Mount SMD Fuse, 0451.630MR, 630 mA, 125 V AC/DC, Fast Blow, 50 A breaking capacity, 2-SMD Square End Block package, Tape & Reel.","salesMarkdown":"## 630 mA fast blow in a 2.69 mm profile The Littelfuse 0451.630MR is a 630 mA fast-blow SMD fuse from the NANO² 451 series, rated for 125 V AC and DC with a breaking capacity of 50 A at rated voltage. The 0.143 melting I²t means it clears quickly on a hard short, but the energy let-through is low enough to protect downstream traces and components rated for that threshold. The 0.305 Ohm DC cold resistance at 630 mA produces about 120 mW self-heating at rated current — negligible in free air, but in a dense SMD layout the adjacent parts see that thermal rise. ## Obsolete — sourcing the 0451.630MR today Available through independent distribution and surplus channels; stock is lot-specific and traceable. No official successor order code is recorded from Littelfuse for this exact package and rating. A board-level review of the 451 series parametric range is the practical path to a replacement. ## Package, approvals, and temperature range Housed in a 2-SMD square end block package measuring 6.10 mm x 2.69 mm x 2.69 mm, surface-mount only — the end caps are the termination, no leads to bend or trim. CSA and UL approved — the UL recognition covers the 50 A interrupting rating at 125 V AC/DC, so it passes the branch-circuit protection requirements for most low-power DC rails and control transformers.","metaTitle":"0451.630MR Littelfuse NANO² 451, 630mA Fast Blow SMD Fuse","metaDescription":"Littelfuse 0451.630MR NANO² 451 SMD fuse, 630mA, 125V AC/DC, 50A breaking capacity. Obsolete — sourced to order. UL/CSA approved.","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":"0.143","Mounting Type":"Surface Mount","Response Time":"Fast Blow","Package / Case":"2-SMD, Square End Block","Product Status":"Obsolete","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":"0.305 Ohms","Voltage Rating - AC":"125 V","Voltage Rating - DC":"125 V","Current Rating (Amps)":"630 mA","Operating Temperature":"-55°C~125°C","Breaking Capacity @ Rated Voltage":"50A"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":"$2.7000","stockQuantity":0,"priceTiers":null},"links":{"datasheetUrl":"https://cdn.icboms.com/604a0e4c498aa97d2607992508357d04.pdf","sourceUrl":null},"ai":{"faq":[{"question":"What approvals does the 0451.630MR carry?","answer":"The 0451.630MR is CSA and UL approved. The UL listing covers the 50 A interrupting rating at 125 V AC and DC, which is the standard branch-circuit protection level for this fuse class."},{"question":"What is the 0451.630MR's melting I²t and why does it matter?","answer":"The melting I²t is 0.143. This is the energy required to melt the fuse element. For a 630 mA fast-blow fuse, a low I²t means it clears very quickly on a short circuit — the downstream components see less thermal stress, but it also means the fuse may nuisance-blow on high inrush currents from capacitive loads."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"icboms-matrix-langgraph","citationUrl":"https://icboms.com/littelfuse-inc/0451.630MR","citationPolicyUrl":"https://icboms.com/llms.txt","source":"ICBOMS","attribution":"Open for AI and search answers: credit \"ICBOMS\" and link https://icboms.com/littelfuse-inc/0451.630MR 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}}