ZHCSP51B december   2020  – may 2023 LMR43610 , LMR43620

PRODUCTION DATA  

  1.   1
  2. 1 特性
  3. 2 应用
  4. 3 说明
  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  Enable, Start-Up, and Shutdown
      2. 8.3.2  External CLK SYNC (with MODE/SYNC)
        1. 8.3.2.1 Pulse-Dependent MODE/SYNC Pin Control
      3. 8.3.3  Adjustable Switching Frequency (with RT)
      4. 8.3.4  Power-Good Output Operation
      5. 8.3.5  Internal LDO, VCC, and VOUT/FB Input
      6. 8.3.6  Bootstrap Voltage and VBOOT-UVLO (BOOT Terminal)
      7. 8.3.7  Output Voltage Selection
      8. 8.3.8  Soft Start and Recovery from Dropout
        1. 8.3.8.1 Recovery from Dropout
      9. 8.3.9  Current Limit and Short Circuit
      10. 8.3.10 Thermal Shutdown
      11. 8.3.11 Input Supply Current
    4. 8.4 Device Functional Modes
      1. 8.4.1 Shutdown Mode
      2. 8.4.2 Standby Mode
      3. 8.4.3 Active Mode
        1. 8.4.3.1 CCM Mode
        2. 8.4.3.2 Auto Mode – Light-Load Operation
          1. 8.4.3.2.1 Diode Emulation
          2. 8.4.3.2.2 Frequency Reduction
        3. 8.4.3.3 FPWM Mode – Light-Load Operation
        4. 8.4.3.4 Minimum On-Time (High Input Voltage) Operation
        5. 8.4.3.5 Dropout
  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 Choosing the Switching Frequency
        2. 9.2.2.2 Setting the Output Voltage
          1. 9.2.2.2.1 FB for Adjustable Output
        3. 9.2.2.3 Inductor Selection
        4. 9.2.2.4 Output Capacitor Selection
        5. 9.2.2.5 Input Capacitor Selection
        6. 9.2.2.6 CBOOT
        7. 9.2.2.7 VCC
        8. 9.2.2.8 CFF Selection
          1. 9.2.2.8.1 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 第三方产品免责声明
      2. 10.1.2 Device Nomenclature
    2. 10.2 Documentation Support
      1. 10.2.1 Related Documentation
    3. 10.3 支持资源
    4. 10.4 Trademarks
    5. 10.5 静电放电警告
    6. 10.6 术语表
  12. 11Mechanical, Packaging, and Orderable Information

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8.3.8.1 Recovery from Dropout

Any time the output voltage falls more than a few percent, output voltage ramps up slowly. This condition, called graceful recovery from dropout in this document, differs from soft start in two important ways:

  • The reference voltage is set to approximately 1% above what is needed to achieve the existing output voltage.
  • If the device is set to FPWM, the device continues to operate in that mode during its recovery from dropout. If output voltage were to suddenly be pulled up by an external supply, the LMR436x0 can pull down on the output. Note that all protections that are present during normal operation are in place, preventing any catastrophic failure if output is shorted to a high voltage or ground.
GUID-543844B3-C34C-44D9-9AC6-5B7A36BE0572-low.gifFigure 8-11 Recovery from Dropout
GUID-59E7153F-C2F4-4E06-9337-C6F0E7329C10-low.gifFigure 8-12 Typical Output Recovery from Dropout from 8 V to 4 V

Whether output voltage falls due to high load or low input voltage, after the condition that causes output to fall below its set point is removed, the output climbs at the same speed as during start-up. Figure 8-12 shows an example of this behavior.