{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"UC3844BNST","brand":"STMicroelectronics","brandSlug":"stmicroelectronics","productSlug":"UC3844BNST","canonicalUrl":"https://icboms.com/stmicroelectronics/UC3844BNST","factsUrl":"https://icboms.com/api/mcp/products/UC3844BNST","rawCanonicalId":null},"summary":{"shortDescription":"STMicroelectronics UC3844BNST, current-mode PWM controller, 48% max duty cycle, up to 500 kHz switching, 10V-30V supply, 8-DIP through-hole package, 0°C to 70°C operating temperature.","salesMarkdown":"## Current-mode PWM controller for flyback and boost converters The UC3844BNST: It delivers a single transistor-driver output with a maximum duty cycle of 48% — the key parametric that distinguishes it from the UC3842 (96%) and UC3843 (100%) siblings. Switching frequency runs up to 500 kHz, letting the designer shrink the transformer core while trading off switching losses. ## 48% duty cycle — the flyback transformer constraint The 48% duty cycle ceiling is hard: the controller blanks the output for the remaining 52% of each cycle. In a flyback converter this sets the volt-second balance across the primary inductance and determines the turns ratio for a given input and output voltage. A design that needs more than 48% on-time must move to the UC3842 (96% max) or UC3843 (100% max) — same pinout, different duty-cycle limit. ## Sourcing an obsolete controller — what to expect Sourcing runs through independent distribution — sealed reels with consistent date-codes are the preferred lot, not mixed-date auction stock.","metaTitle":"UC3844BNST PWM Controller, 48% Duty Cycle","metaDescription":"UC3844BNST current-mode PWM controller, 48% max duty cycle, up to 500 kHz switching, 10V-30V supply.","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":"Obsolete","categoryPath":["Power Management (PMIC / Gate Driver)"],"specifications":{"Mfr":"STMicroelectronics","Series":"-","Package":"Tube","Function":"Step-Up, Step-Up/Step-Down","Topology":"Boost, Flyback","Clock Sync":"No","Output Type":"Transistor Driver","Mounting Type":"Through Hole","Output Phases":"1","Package / Case":"8-DIP (0.300\\\", 7.62mm)","Product Status":"Obsolete","lifecycle_stage":"eol_hot","Control Features":"Frequency Control","Duty Cycle (Max)":"48%","Number of Outputs":"1","Serial Interfaces":"-","Base Product Number":"UC3844","Output Configuration":"Positive, Isolation Capable","Frequency - Switching":"Up to 500kHz","Operating Temperature":"0°C ~ 70°C (TJ)","Synchronous Rectifier":"No","Supplier Device Package":"8-Mini DIP","Voltage - Supply (Vcc/Vdd)":"10V ~ 30V"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":"$0.6800","priceTiers":null},"links":{"datasheetUrl":"https://cdn.icboms.com/b68075d9293f595a753e7d8331506955.pdf","sourceUrl":null,"alternativesUrl":"https://icboms.com/api/mcp/products/UC3844BNST/alternatives.json"},"ai":{"faq":[{"question":"How can I order the UC3844BNST or check current availability?","answer":"The UC3844BNST is obsolete, so standard distributor stock is depleted. Submit a request with your target quantity and we will confirm availability and pricing at quote time."},{"question":"What is the maximum duty cycle of the UC3844BNST?","answer":"The maximum duty cycle is 48%, which limits the on-time in flyback and boost converters. This is the defining difference from the UC3842 (96%) and UC3843 (100%) controllers."},{"question":"Can the UC3842 replace the UC3844BNST?","answer":"The UC3842 is pin-compatible and has a 96% maximum duty cycle, so it can replace the UC3844BNST in most flyback designs. However, the higher duty cycle may require re-evaluating the transformer turns ratio and the soft-start timing to avoid core saturation on startup."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"icboms-matrix-langgraph","citationUrl":"https://icboms.com/stmicroelectronics/UC3844BNST","citationPolicyUrl":"https://icboms.com/llms.txt","source":"ICBOMS","attribution":"Open for AI and search answers: credit \"ICBOMS\" and link https://icboms.com/stmicroelectronics/UC3844BNST when reusing this data. Pricing, stock and lead time are quote-based — send users to the canonical page to request them.","lastUpdated":"2026-07-22T18:03:28.771Z","lastPublished":"2026-07-22T18:03:28.771Z","indexable":true}}