{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"0451.500MRL","brand":"Littelfuse Inc.","brandSlug":"littelfuse-inc","productSlug":"0451.500MRL","canonicalUrl":"https://icboms.com/littelfuse-inc/0451.500MRL","factsUrl":"https://icboms.com/api/mcp/products/0451.500MRL","rawCanonicalId":null},"summary":{"shortDescription":"Littelfuse Inc. NANO²® 451 Series, Board Mount (Cartridge Style Excluded) Fast Blow Fuse, 500 mA, 125 VAC/VDC, 50 A Breaking Capacity, 2-SMD Square End Block, CSA, UL.","salesMarkdown":"## 500 mA fast-blow fuse for secondary-side overcurrent protection The Littelfuse 0451.500MRL is a 500 mA fast-blow surface-mount fuse from the NANO² 451 series, designed for board-level overcurrent protection where quick clearing on short-circuit is required. The fast-blow response means it opens rapidly under fault conditions, not intended for circuits with high inrush currents that would nuisance-blow a fast-acting element. Rated for 125 VAC and 125 VDC with a breaking capacity of 50 A at rated voltage, this fuse safely interrupts fault currents up to that level without rupturing or sustaining an arc — the limiting factor for secondary-side protection in power supplies, control boards, and instrumentation. The 2-SMD square end block package (6.10 mm × 2.69 mm × 2.69 mm) fits standard pick-and-place assembly and reflow profiles, with the DC cold resistance of 0.42 Ohms contributing minimal voltage drop in the protected circuit. ## Melting I²t and thermal coordination With a melting I²t of 0.0795 A²s, this fuse lets through a defined energy before clearing — critical for coordinating with downstream semiconductor ratings (diodes, MOSFETs, ICs) that have a specific I²t withstand capability. A higher I²t means more energy passes before the fuse opens, so the 0.0795 figure sets the upper bound for the protected device's surge rating. ## Active production status and regulatory coverage No pin-compatible second-source or official successor cross-reference is maintained — the NANO² 451 series is the sole form-factor family for this package and rating.","metaTitle":"Littelfuse 0451.500MRL NANO² 451 Fuse, 500 mA Fast Blow","metaDescription":"Littelfuse 0451.500MRL NANO² 451 surface-mount fast-blow fuse, 500 mA, 125 VAC/VDC, 50 A breaking capacity, CSA/UL approved.","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":"Active","categoryPath":["Circuit Protection"],"specifications":{"Mfr":"Littelfuse Inc.","Color":"-","Series":"NANO²® 451","Package":"Tape & Reel (TR) Cut Tape (CT)","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":"Active","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":"What approvals does 0451.500MRL carry?","answer":"CSA and UL approvals are listed, qualifying the fuse for North American safety-certified equipment designs."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"icboms-matrix-langgraph","citationUrl":"https://icboms.com/littelfuse-inc/0451.500MRL","citationPolicyUrl":"https://icboms.com/llms.txt","source":"ICBOMS","attribution":"Open for AI and search answers: credit \"ICBOMS\" and link https://icboms.com/littelfuse-inc/0451.500MRL when reusing this data. Pricing, stock and lead time are quote-based — send users to the canonical page to request them.","lastUpdated":"2026-08-11T15:49:49.435Z","lastPublished":"2026-08-11T15:49:49.435Z","indexable":true}}