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Datasheet Linear Technology LT8309ES5#PBF

ManufacturerLinear Technology
Part NumberLT8309ES5#PBF

Secondary-Side Synchronous Rectifier Driver


  • Download » Datasheet, PDF, 232 Kb, File uploaded 07-31-2016
    LT8309: Secondary-Side Synchronous Rectifier Driver Data Sheet
    Docket ↓
    Synchronous Rectifier Driver
    Features Description Works with DCM and BCM/CrCM Conduction Mode
    Flyback Topologies
    n V : 4.5V to 40V
    n Supports Up to 150V MOSFETs
    n 26ns Turn-Off Propagation Delay
    n Accurate Minimum On and Off Timers for Reliable
    Operatio Adjustable and Accurate Trip Point: +5mV to –30mV
    n 1Ω Gate Driver Pull-Dow SOT-23 5-Lead Package The LT®8309 is a secondary-side synchronous rectifier
    driver that replaces the output rectifier diode in a flyback
    topology. By replacing the diode with a N-channel MOSFET,
    applications are no longer restricted by the heat constraints
    of the output diode. The IC replicates the behavior of a
    diode by sensing the drain-to-source voltage to determine
    when the current becomes negative. The LT8309's low
    minimum on-and off-times help improve noise immunity. n The fast propagation delay of 26ns allows applications to
    operate in discontinuous conduction mode (DCM) and
    critical conduction mode (CrCM). The gate driver features
    a 0.8Ω pull-down device for fast turn-offs. The 40V VCC
    rating allows the part to be driven from the output voltage or the rectified drain voltage of the MOSFET. A low ...



Package CodeS5
Package Index05-08-1635


Demo BoardsDC1961A
Design ToolsLTspice File
Export Controlno
Integrated Inductorno
Number of Outputs1
Operating Temperature Range0 to 85 °C
TopologyFlyback Synchronous Rectifier
Vin Max40 V
Vin Min4.5 V

Eco Plan



  • Download » Articles - LT Journal, PDF, 376 Kb, 01-06-2014
    Increase Current Capability and Simplify Thermal Design of Flyback Converters with Secondary-Side Synchronous Rectifier Driver in a 5-Pin SOT-23
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    Increase Current Capability and Simplify Thermal Design
    of Flyback Converters with Secondary-Side Synchronous
    Rectifier Driver in a 5-Pin SOT-23
    Wei Gu In a flyback converter, current levels in high current applications are constrained
    by heat produced in the output rectifier diode. The clear way to lift this restriction
    is to replace the diode with a much lower voltage drop MOSFET, significantly
    reducing heat produced in the rectifier—reduced heat dissipation increases output
    current capability and efficiency, and simplifies thermal design. The LT8309 is a
    secondary-side synchronous MOSFET driver that replicates the behavior of the
    output diode by sensing the drain-to-source voltage of the MOSFET to determine
    if should be on or off, allowing it to replace a less efficient rectifier diode.
    The LT8309 can be combined with any
    of Linear’s line of no-opto boundarymode flyback ICs (such as the LT3748
    primary side controller) to produce high
    performance isolated power supplies
    with a minimal number of components.
    5V, 8A ISOLATED SUPPLY Figure 1 shows a low voltage, high
    current, low parts count flyback
    supply. The traditional output diode is
    replaced by an ideal diode consisting
    of the LT8309, a MOSFET and a few
    small external components.
    For a MOSFET to act as a diode it must ...

Moldel Line

Series: LT8309 (9)

Manufacturer's Classification

  • Power Management > Switching Regulator > Flyback, Forward and Isolated Controllers
  • Space & Harsh Environment > Extended Temperature Plastic (H & MP) > Extended Temperature (H & MP) Power Management
  • Power Management > Power Control > Secondary Side Controllers

Other Names:


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