JAJSHB8A May   2019  – October 2019 LMR34206-Q1

PRODUCTION DATA.  

  1. 1 特長
  2. 2 アプリケーション
  3. 3 概要
    1.     Device Images
      1. 3.1 概略回路図
  4. 4 改訂履歴
  5. 5 概要（続き）
  6. 6 Device Comparison Table
  7. 7 Pin Configuration and Functions
    1.     Pin Functions
  8. 8 Specifications
    1. 8.1 Absolute Maximum Ratings
    2. 8.2 ESD Ratings
    3. 8.3 Recommended Operating Conditions
    4. 8.4 Thermal Information
    5. 8.5 Electrical Characteristics
    6. 8.6 Timing Requirements
    7. 8.7 System Characteristics
    8. 8.8 Typical Characteristics
  9. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1 Power-Good Flag Output
      2. 9.3.2 Enable and Start-up
      3. 9.3.3 Current Limit and Short Circuit
      4. 9.3.4 Undervoltage Lockout and Thermal Shutdown
    4. 9.4 Device Functional Modes
      1. 9.4.1 Auto Mode
      2. 9.4.2 Forced PWM Operation
      3. 9.4.3 Dropout
      4. 9.4.4 Minimum Switch On-Time
      5. 9.4.5 Spread Spectrum Operation
  10. 10Application and Implementation
    1. 10.1 Application Information
    2. 10.2 Typical Application
      1. 10.2.1 Design Requirements
        1. 10.2.1.1 Design Requirements
      2. 10.2.2 Detailed Design Procedure
        1. 10.2.2.1 Choosing the Switching Frequency
        2. 10.2.2.2 Setting the Output Voltage
        3. 10.2.2.3 Inductor Selection
        4. 10.2.2.4 Output Capacitor Selection
        5. 10.2.2.5 Input Capacitor Selection
        6. 10.2.2.6 CBOOT
        7. 10.2.2.7 VCC
        8. 10.2.2.8 External UVLO
        9. 10.2.2.9 Maximum Ambient Temperature
      3. 10.2.3 Application Curves
  11. 11Power Supply Recommendations
  12. 12Layout
    1. 12.1 Layout Guidelines
      1. 12.1.1 Ground and Thermal Considerations
    2. 12.2 Layout Example
  13. 13デバイスおよびドキュメントのサポート
    1. 13.1 デバイス・サポート
      1. 13.1.1 開発サポート
    2. 13.2 ドキュメントのサポート
      1. 13.2.1 関連資料
    3. 13.3 ドキュメントの更新通知を受け取る方法
    4. 13.4 サポート・リソース
    5. 13.5 商標
    6. 13.6 静電気放電に関する注意事項
    7. 13.7 Glossary
  14. 14メカニカル、パッケージ、および注文情報

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

9.4.3 Dropout

The dropout performance of any buck regulator is affected by the RDSON of the power MOSFETs, the DC resistance of the inductor, and the maximum duty cycle that the controller can achieve. As the input voltage is reduced to near the output voltage, the off-time of the high-side MOSFET starts to approach the minimum value. Beyond this point the switching may become erratic and/or the output voltage falls out of regulation. To avoid this problem the LMR34206-Q1 automatically reduces the switching frequency to increase the effective duty cycle and maintain regulation. In this data sheet the dropout voltage is defined as the difference between the input and output voltage when the output has dropped by 1% of its nominal value. Under this condition the switching frequency has dropped to its minimum value of about 140 kHz. Note that the 0.4 V short circuit detection threshold is not activated when in dropout mode. Typical dropout characteristics can be found in Figure 15 and Figure 16.

LMR34206-Q1 lmr34206fsc5_voltage_dropout_.gifFigure 15. Overall Dropout Characteristic
VOUT = 5 V
LMR34206-Q1 lmr34206fsc5_frequency_dropout_.gifFigure 16. Typical ƒSW vs Output Current
ƒSW = 2100 kHz