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Synchronous Forward MOSFET Driver Eliminates Signal Transformer

Apr 2 2014 - MILPITAS, CA
  • Linear Technology Corporation announces the LT8311, a high efficiency secondary-side MOSFET driver that operates without the need for primary control in an isolated synchronous forward converter. The LT8311’s unique preactive mode eliminates the need for a signal transformer for primary to secondary-side communication by sensing signals on the secondary side to control synchronous rectification. This mode reduces component count and solution size.


    The LT8311 operates over a 3.7V to 30V input voltage range and is used with a primary-side IC, such as the LT3752/-1. The complete forward converter can operate with input voltages ranging from 6.5V up to 400V+ making it ideal for a wide range of applications including hybrid/electric vehicle automotive requirements. Furthermore, the LT8311 combines a 10mA opto-driver and a feedback loop error amplifier to enable output voltage feedback from the secondary to the primary side. The entire system provides fixed frequency peak current mode control that has excellent line/load regulation and fast transient response. Additional features include a 1.5% reference voltage, a power good monitor and programmable soft-start of the output voltage.


    The LT8311 is available in a TSSOP-20 package with several pins removed for high peak voltage spacing. The LT8311 E- and I-grade versions operate from a –40°C to 125°C junction temperature. The LT8311 H grade is guaranteed to operate from a –40°C to 150°C operating junction temperature. The LT8311 MP grade is guaranteed to operate from –55°C to 150°C operating junction temperature. The 1,000-piece price starts at $3.06 each. For more information, visit www.linear.com/product/LT8311.


    Summary of Features: LT8311


    • Eliminates Signal Transformer for Synchronous Rectification Control
    • LT8311 Input Voltage Range: 3.7V to 30V
    • Operates with Primary-Side IC for up to 400V+ Input Voltages
    • 1.5% Reference Voltage
    • On-board 10mA Opto-Coupler Driver
    • Output Power Good Indicator
    • Programmable Soft-Start of Output Voltage
    • On-board Feedback Error Amplifier
    • Extended & Industrial Grades: –40°C to 125°C Operating Junction Temp
    • Automotive Temp Grade: –40°C to 150°C Operating Junction Temp
    • Military Temp Grade: –55°C to 150°C Operating Junction Temp

    Synchronous Forward MOSFET Driver

    LT8311 PR Image

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