JAJSEV3B June   2017  – August 2020 LMR23615

PRODUCTION DATA  

  1. 1 特長
  2. 2 アプリケーション
  3. 3 概要
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin Functions
  6. 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 Characteristics
    7. 6.7 Switching Characteristics
    8. 6.8 Typical Characteristics
  7. 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 Frequency
      3. 7.3.3  Adjustable Output Voltage
      4. 7.3.4  Enable/Sync
      5. 7.3.5  VCC, UVLO
      6. 7.3.6  Minimum ON-Time, Minimum-OFF Time, and Frequency Foldback at Dropout Conditions
      7. 7.3.7  Internal Compensation and CFF
      8. 7.3.8  Bootstrap Voltage (BOOT)
      9. 7.3.9  Overcurrent and Short-Circuit Protection
      10. 7.3.10 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
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1  Custom Design With WEBENCH® Tools
        2. 8.2.2.2  Output Voltage Setpoint
        3. 8.2.2.3  Switching Frequency
        4. 8.2.2.4  Inductor Selection
        5. 8.2.2.5  Output Capacitor Selection
        6. 8.2.2.6  Feedforward Capacitor
        7. 8.2.2.7  Input Capacitor Selection
        8. 8.2.2.8  Bootstrap Capacitor Selection
        9. 8.2.2.9  VCC Capacitor Selection
        10. 8.2.2.10 Undervoltage Lockout Setpoint
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 Compact Layout for EMI Reduction
      2. 10.1.2 Ground Plane and Thermal Considerations
      3. 10.1.3 Feedback Resistors
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Development Support
        1. 11.1.1.1 Custom Design With WEBENCH® Tools
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Support Resources
    4. 11.4 Trademarks
    5. 11.5 静電気放電に関する注意事項
    6. 11.6 Glossary
  12. 12Mechanical, 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

7.3.2 Adjustable Frequency

The switching frequency can be programmed by the resistor from the RT pin to ground. The frequency is inversely proportional to the RT resistance. The RT pin can be left floating, and the LMR23615 operates at 400-kHz default switching frequency. The RT pin is not designed to be shorted to ground. For a desired frequency, typical RT resistance can be found by Equation 1. Table 7-1 gives typical RT values for a given switching frequency (fSW ).

Equation 1. RT(kΩ) = 40200 / fSW(kHz) – 0.6
GUID-DEF90936-2F3B-473F-BB72-8F7A67482CFC-low.pngFigure 7-2 RT vs Frequency Curve
Table 7-1 Typical Frequency Setting RT Resistance
fSW (kHz) RT (kΩ)
200200
350115
50078.7
75053.6
100039.2
150026.1
200019.6
220017.8