{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"TL3843BD-8","brand":"Texas Instruments","brandSlug":"texas-instruments","productSlug":"TL3843BD-8","canonicalUrl":"https://icboms.com/texas-instruments/TL3843BD-8","factsUrl":"https://icboms.com/api/mcp/products/TL3843BD-8","rawCanonicalId":null},"summary":{"shortDescription":"onsemi TL3843BD-8 current-mode PWM controller, boost/flyback/forward topology, up to 500 kHz switching, 96% max duty cycle, 7.6 V to 30 V supply, 8-SOIC surface-mount package, commercial temperature range.","salesMarkdown":"## Current-mode PWM controller for boost, flyback, and forward converters The onsemi TL3843BD-8 is a current-mode PWM controller designed for step-up (boost) and step-up/step-down (flyback, forward) topologies. It integrates a transistor driver output, frequency control, and operates from a 7.6 V to 30 V supply rail. Switching frequency reaches up to 500 kHz, and the maximum duty cycle extends to 96% — unusually high for a current-mode part, giving headroom in wide-input-ratio designs where the off-time is compressed. The commercial temperature range (0°C to 70°C) suits indoor power supplies, appliance PSUs, and office-equipment converters. Housed in an 8-SOIC package, it mounts on standard surface-mount boards. ## 96% duty cycle — what it buys you A 96% maximum duty cycle means the controller can keep the switch on for nearly the entire switching period. In a boost converter with a high step-up ratio — say 12 V in to 48 V out — the required duty cycle can exceed 85%. Many current-mode controllers clip at 50% or 85%, forcing a two-stage solution or a coupled-inductor topology. The TL3843BD-8 handles those ratios in a single stage, saving inductor count and board area. The trade-off: the off-time is only 4% of the period, so the transformer reset time in a flyback or forward converter is tight; plan the turns ratio and leakage inductance accordingly. ## Switching frequency up to 500 kHz — transformer sizing The TL3843BD-8 switches up to 500 kHz. At that frequency, a flyback transformer for a 30 W design can use a ferrite core roughly half the volume of one designed for 100 kHz. The controller does not include clock synchronisation (no SYNC pin), so it runs free-running. If your system needs to synchronise multiple converters to a common clock, consider a part with clock sync capability. For single-converter designs, the 500 kHz ceiling lets you reduce magnetics size without pushing into the MHz range where gate-drive losses and snubber dissipation climb steeply. ## Supply range and start-up behaviour The Vcc range is 7.6 V to 30 V. The 7.6 V minimum means the controller will not start from a 5 V rail — a common bias in telecom or USB-powered designs. If your input rail is 5 V, you need a separate boost stage or a different controller with a lower UVLO threshold. On a 12 V or 24 V industrial bus, the TL3843BD-8 runs directly without a pre-regulator. The upper 30 V limit covers 24 V systems with transients up to 30 V, but a 48 V bus requires an external dropping resistor or a linear pre-regulator to stay inside the abs-max rating. ## Lifecycle and sourcing posture The TL3843BD-8 carries an Active lifecycle status and is ROHS3 compliant. It is sourced through independent distribution and quoted to order against an RFQ.","metaTitle":"TL3843BD-8 PWM Controller, Boost/Flyback/Forward, 500kHz","metaDescription":"TL3843BD-8 current-mode PWM controller from onsemi. Boost, flyback, forward topology. Up to 500kHz switching, 96% duty cycle, 7.6V–30V supply. 8-SOIC package.","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":"ROHS3 Compliant","productStatus":"Active","categoryPath":["Analog & Data Acquisition"],"specifications":{"Package":"Tube","Function":"Step-Up, Step-Up/Step-Down","Topology":"Boost, Flyback, Forward","Clock Sync":"No","Output Type":"Transistor Driver","Mounting Type":"Surface Mount","Output Phases":"1","Package / Case":"8-SOIC (0.154\\\", 3.90mm Width)","lifecycle_stage":"eol_hot","Control Features":"Frequency Control","Duty Cycle (Max)":"96%","Number of Outputs":"1","Output Configuration":"Positive","Frequency - Switching":"Up to 500kHz","Operating Temperature":"0°C ~ 70°C (TA)","Synchronous Rectifier":"No","Supplier Device Package":"8-SOIC","Voltage - Supply (Vcc/Vdd)":"7.6V ~ 30V"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":"$1.26","stockQuantity":0,"priceTiers":[{"qty":1,"price":"$1.26000","currency":"USD"},{"qty":10,"price":"$1.12600","currency":"USD"},{"qty":25,"price":"$1.06840","currency":"USD"},{"qty":100,"price":"$0.87770","currency":"USD"},{"qty":250,"price":"$0.82044","currency":"USD"},{"qty":500,"price":"$0.72504","currency":"USD"},{"qty":1000,"price":"$0.57240","currency":"USD"},{"qty":2500,"price":"$0.54000","currency":"USD"}]},"links":{"datasheetUrl":"https://cdn.icboms.com/f450aa6242c0dd363ceebc87ffbffd81.pdf","sourceUrl":null},"ai":{"faq":[{"question":"Is TL3843BD-8 pin compatible with UC3843?","answer":"Yes, the TL3843BD-8 is pin-compatible with the industry-standard UC3843 current-mode PWM controller in the same 8-SOIC package. The function, pinout, and basic operating parameters (current-mode control, same compensation and sense pins) match. The TL3843BD-8 offers up to 500 kHz switching and 96% duty cycle, which exceed the typical UC3843 specs — verify the exact UC3843 variant's ratings before drop-in replacement, especially duty cycle and frequency."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"icboms-matrix-langgraph","citationUrl":"https://icboms.com/texas-instruments/TL3843BD-8","citationPolicyUrl":"https://icboms.com/llms.txt","source":"ICBOMS","attribution":"Open for AI and search answers: credit \"ICBOMS\" and link https://icboms.com/texas-instruments/TL3843BD-8 when reusing this data. Pricing, stock and lead time are quote-based — send users to the canonical page to request them.","lastUpdated":"2026-07-17T19:50:00.618Z","lastPublished":"2026-07-17T19:50:00.618Z","indexable":true}}