ZHCSN09A June   2021  – September 2022 LM5168-Q1 , LM5169-Q1

PRODUCTION DATA  

  1. 1 特性
  2. 2 应用
  3. 3 说明
  4. 4 Revision History
  5. 5 Device Comparison Table
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1  Control Architecture
      2. 8.3.2  Internal VCC Regulator and Bootstrap Capacitor
      3. 8.3.3  Internal Soft Start
      4. 8.3.4  On-Time Generator
      5. 8.3.5  Current Limit
      6. 8.3.6  N-Channel Buck Switch and Driver
      7. 8.3.7  Synchronous Rectifier
      8. 8.3.8  Enable, Undervoltage Lockout (EN/UVLO)
      9. 8.3.9  Power Good (PGOOD)
      10. 8.3.10 Thermal Protection
    4. 8.4 Device Functional Modes
      1. 8.4.1 Shutdown Mode
      2. 8.4.2 Active Mode
      3. 8.4.3 Sleep Mode
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Fly-Buck™ Converter Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1  Switching Frequency (RT)
        2. 9.2.2.2  Transformer Selection
        3. 9.2.2.3  Output Capacitor Selection
        4. 9.2.2.4  Secondary Output Diode
        5. 9.2.2.5  Setting Output Voltage
        6. 9.2.2.6  Input Capacitor
        7. 9.2.2.7  Type-3 Ripple Network
        8. 9.2.2.8  CBST Selection
        9. 9.2.2.9  Minimum Secondary Output Load
        10. 9.2.2.10 Example Design Summary
      3. 9.2.3 Application Curves
    3. 9.3 Typical Buck Application
      1. 9.3.1 Design Requirements
      2. 9.3.2 Detailed Design Procedure
        1. 9.3.2.1 Switching Frequency (RT)
        2. 9.3.2.2 Buck Inductor Selection
        3. 9.3.2.3 Setting the Output Voltage
        4. 9.3.2.4 Type-3 Ripple Network
        5. 9.3.2.5 Output Capacitor Selection
        6. 9.3.2.6 Input Capacitor Considerations
        7. 9.3.2.7 CBST Selection
        8. 9.3.2.8 Example Design Summary
      3. 9.3.3 Application Curves
    4. 9.4 Power Supply Recommendations
    5. 9.5 Layout
      1. 9.5.1 Thermal Considerations
      2. 9.5.2 Typical EMI Results
      3. 9.5.3 Layout Guidelines
        1. 9.5.3.1 Compact PCB Layout for EMI Reduction
        2. 9.5.3.2 Feedback Resistors
      4. 9.5.4 Layout Example
  10. 10Device and Documentation Support
    1. 10.1 Device Support
      1. 10.1.1 第三方产品免责声明
    2. 10.2 Documentation Support
      1. 10.2.1 Related Documentation
    3. 10.3 接收文档更新通知
    4. 10.4 支持资源
    5. 10.5 Trademarks
    6. 10.6 Electrostatic Discharge Caution
    7. 10.7 术语表
  11. 11Mechanical, Packaging, and Orderable Information

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9.2.2.4 Secondary Output Diode

The secondary output diode must block the maximum input voltage reflected to the secondary by the transformer turns ratio. Equation 17 is used to determine the maximum reverse voltage on the diode. For this example, a value of 70 V is calculated and a 100-V diode is chosen. The diode current rating should be at least equal to the secondary output current with an appropriate factor of safety. Schottky diodes are the best choice for this application. Ultra-fast recovery diodes can also be used. In any case, choose a diode with the lowest turn-off time.

Equation 17.