ZHCSN38D October   2021  – April 2024 LMR54406 , LMR54410

PRODUCTION DATA  

  1.   1
  2. 1 特性
  3. 2 应用
  4. 3 说明
  5. 4 Device Comparison Table
  6. 5 Pin Configuration and Functions
  7. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Timing Requirements
    7. 6.7 System Characteristics
    8. 6.8 Typical Characteristics
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Fixed Frequency Peak Current Mode Control
      2. 7.3.2 Adjustable Output Voltage
      3. 7.3.3 Enable
      4. 7.3.4 Minimum ON Time, Minimum OFF Time, and Frequency Foldback
      5. 7.3.5 Bootstrap Voltage
      6. 7.3.6 Overcurrent and Short Circuit Protection
      7. 7.3.7 Soft Start
      8. 7.3.8 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 Shutdown Mode
      2. 7.4.2 Active Mode
      3. 7.4.3 CCM Mode
      4. 7.4.4 Light Load Operation (PFM Version)
      5. 7.4.5 Light-Load Operation (FPWM Version)
  9. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Output Voltage Set-Point
        2. 8.2.2.2 Switching Frequency
        3. 8.2.2.3 Inductor Selection
        4. 8.2.2.4 Output Capacitor Selection
        5. 8.2.2.5 Input Capacitor Selection
        6. 8.2.2.6 Bootstrap Capacitor
        7. 8.2.2.7 Undervoltage Lockout Set-Point
        8. 8.2.2.8 Replacing Non Sync Converter
      3. 8.2.3 Application Curves
    3. 8.3 Power Supply Recommendations
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
        1. 8.4.1.1 Compact Layout for EMI Reduction
        2. 8.4.1.2 Feedback Resistors
      2. 8.4.2 Layout Example
  10. 9 Device and Documentation Support
    1. 9.1 Device Support
      1. 9.1.1 第三方产品免责声明
    2. 9.2 Documentation Support
      1. 9.2.1 Related Documentation
    3. 9.3 接收文档更新通知
    4. 9.4 支持资源
    5. 9.5 Trademarks
    6. 9.6 静电放电警告
    7. 9.7 术语表
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information

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7.3.2 Adjustable Output Voltage

A precision 0.8-V reference voltage (VREF) is used to maintain a tightly regulated output voltage over the entire operating temperature range. The output voltage is set by a resistor divider from VOUT to the FB pin. TI recommends to use 1% tolerance resistors with a low temperature coefficient for the FB divider. Select the bottom-side resistor, RFBB, for the desired divider current and use Equation 1 to calculate the top-side resistor, RFBT. The recommended range for RFBT is 10 kΩ to 100 kΩ. A lower RFBT value can be used if pre-loading is desired to reduce the VOUT offset in PFM operation. Lower RFBT values reduce efficiency at very light load. Less static current goes through a larger RFBT value and can be more desirable when light-load efficiency is critical. However, RFBT values larger than 1 MΩ are not recommended because they make the feedback path more susceptible to noise. Larger RFBT values require a more carefully designed feedback path trace from the feedback resistors to the feedback pin of the device. The tolerance and temperature variation of the resistor divider network affect the output voltage regulation.

GUID-2D35C367-35F2-4940-81FF-7ABCA61F6938-low.gifFigure 7-2 Output Voltage Setting
Equation 1. GUID-099F4B92-B57C-494B-879A-027AEA2D4D83-low.gif