{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"0451.500MR","brand":"Littelfuse Inc.","brandSlug":"littelfuse-inc","productSlug":"0451.500MR","canonicalUrl":"https://icboms.com/littelfuse-inc/0451.500MR","factsUrl":"https://icboms.com/api/mcp/products/0451.500MR","rawCanonicalId":null},"summary":{"shortDescription":"Littelfuse Inc. NANO²® 451 series, Board Mount Surface Mount Fuse, 500 mA, 125 V AC/125 V DC, Fast Blow, 2-SMD Square End Block, Tape & Reel.","salesMarkdown":"## What this 500 mA fast-blow SMT fuse covers The Littelfuse 0451.500MR is a NANO²® 451 series surface-mount fuse rated 500 mA at 125 V AC and 125 V DC with a fast-blow response. Breaking capacity is 50 A at rated voltage — sufficient for secondary-side protection in power supplies, battery packs, and DC-DC converters where the prospective fault current stays below that threshold. The 2-SMD square end block package measures 6.10 mm x 2.69 mm x 2.69 mm, fitting standard pick-and-place for high-volume assembly. ## Lifecycle reality — obsolete, not orphaned Littelfuse lists the 0451.500MR as obsolete. The NANO² 451 series is a well-known footprint; if a board respin is acceptable, a parametric-equivalent SMT fuse from the same or a competing family may be considered, but no pin-compatible drop-in replacement is documented here. At 500 mA, this fuse protects low-current branches — sensor supplies, control logic rails, or auxiliary loads — where a hard short pulls well above the 50 A interrupting rating. The fast-blow characteristic means it clears quickly on high overcurrents, limiting let-through energy to the downstream components. Melting I²t is 0.0795 A²s — a key figure for coordinating with downstream semiconductor ratings. Approved by CSA and UL — the part carries the agency marks needed for North American equipment compliance without additional fuse testing.","metaTitle":"Littelfuse 0451.500MR NANO² 451 Fuse, 500 mA, 125 V","metaDescription":"Littelfuse 0451.500MR NANO² 451 SMT fuse, 500 mA, 125 V AC/DC, fast blow, 50 A breaking capacity. Obsolete — sourced to order. RFQ for availability.","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":"0.0795","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":"0.42 Ohms","Voltage Rating - AC":"125 V","Voltage Rating - DC":"125 V","Current Rating (Amps)":"500 mA","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":"Where can I buy 0451.500MR and get a price?","answer":"We source the 0451.500MR to order against your BOM line. Submit an RFQ for current pricing and lot availability."},{"question":"What approvals does the 0451.500MR carry?","answer":"The fuse is CSA and UL approved — the agency markings are listed in the spec record, supporting North American regulatory acceptance."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"icboms-matrix-langgraph","citationUrl":"https://icboms.com/littelfuse-inc/0451.500MR","citationPolicyUrl":"https://icboms.com/llms.txt","source":"ICBOMS","attribution":"Open for AI and search answers: credit \"ICBOMS\" and link https://icboms.com/littelfuse-inc/0451.500MR 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}}