JAJSN93B January   2022  – September 2023 LMR38010

PRODUCTION DATA  

  1.   1
  2. 1 特長
  3. 2 アプリケーション
  4. 3 概要
  5. 4 Revision History
  6. 5 Device Comparison Table
  7. 6 Pin Configuration and Functions
  8. 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 System Characteristics
    7. 7.7 Typical Characteristics
  9. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1  Fixed Frequency Peak Current Mode Control
      2. 8.3.2  Adjustable Output Voltage
      3. 8.3.3  Enable
      4. 8.3.4  Switching Frequency and Synchronization (RT/SYNC)
      5. 8.3.5  Power-Good Flag Output
      6. 8.3.6  Minimum On Time, Minimum Off Time, and Frequency Foldback
      7. 8.3.7  Bootstrap Voltage
      8. 8.3.8  Overcurrent and Short Circuit Protection
      9. 8.3.9  Soft Start
      10. 8.3.10 Thermal Shutdown
    4. 8.4 Device Functional Modes
      1. 8.4.1 Auto Mode
      2. 8.4.2 Forced PWM Operation
      3. 8.4.3 Dropout
      4. 8.4.4 Minimum Switch On Time
  10. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 Custom Design With WEBENCH® Tools
        2. 9.2.2.2 Choosing the Switching Frequency
        3. 9.2.2.3 FB for Adjustable Output
        4. 9.2.2.4 Inductor Selection
        5. 9.2.2.5 Output Capacitor Selection
        6. 9.2.2.6 Input Capacitor Selection
        7. 9.2.2.7 CBOOT
        8. 9.2.2.8 External UVLO
        9. 9.2.2.9 Maximum Ambient Temperature
      3. 9.2.3 Application Curves
    3. 9.3 Best Design Practices
    4. 9.4 Power Supply Recommendations
    5. 9.5 Layout
      1. 9.5.1 Layout Guidelines
        1. 9.5.1.1 Ground and Thermal Considerations
      2. 9.5.2 Layout Example
  11. 10Device and Documentation Support
    1. 10.1 Device Support
      1. 10.1.1 Development Support
        1. 10.1.1.1 Custom Design With WEBENCH® Tools
      2. 10.1.2 サード・パーティ製品に関する免責事項
    2. 10.2 Documentation Support
      1. 10.2.1 Related Documentation
    3. 10.3 ドキュメントの更新通知を受け取る方法
    4. 10.4 サポート・リソース
    5. 10.5 Trademarks
    6. 10.6 静電気放電に関する注意事項
    7. 10.7 用語集
  12. 11Mechanical, Packaging, and Orderable Information

パッケージ・オプション

メカニカル・データ（パッケージ｜ピン）
サーマルパッド・メカニカル・データ
発注情報

8.4.4 Minimum Switch On Time

Every switching regulator has a minimum controllable on time dictated by the inherent delays and blanking times associated with the control circuits. This imposes a minimum switch duty cycle, therefore, a minimum conversion ratio. The constraint is encountered at high input voltages and low output voltages. To help extend the minimum controllable duty cycle, the LMR38010 automatically reduces the switching frequency when the minimum on-time limit is reached. This way, the converter can regulate the lowest programmable output voltage at the maximum input voltage. An estimate for the approximate input voltage for a given output voltage, before frequency foldback occurs, is found in Equation 8 . As the input voltage is increased, the switch on time (duty cycle) reduces to regulate the output voltage. When the on time reaches the limit, the switching frequency drops, while the on time remains fixed.

Equation 8. V I N   ≤ V O U T t O N   ×     f S W