ZHCSOA2A July   2020  – July 2021 LM63610-Q1

PRODUCTION DATA  

  1. 1 特性
  2. 2 应用
  3. 3 说明
  4. 4 Revision History
  5. 5 Device Comparison Table
  6. 6 Pin Configuration and Functions
  7. 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 Timing Characteristics
    7. 7.7 Switching Characteristics
    8. 7.8 System Characteristics
    9. 7.9 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Sync/Mode Selection
      2. 8.3.2 Output Voltage Selection
      3. 8.3.3 Switching Frequency Selection
        1. 8.3.3.1 Spread Spectrum Option
      4. 8.3.4 Enable and Start-up
      5. 8.3.5 RESET Flag Output
      6. 8.3.6 Undervoltage Lockout and Thermal Shutdown and Output Discharge
    4. 8.4 Device Functional Modes
      1. 8.4.1 Overview
      2. 8.4.2 Light Load Operation
        1. 8.4.2.1 Sync/FPWM Operation
      3. 8.4.3 Dropout Operation
      4. 8.4.4 Minimum On-time Operation
      5. 8.4.5 Current Limit and Short-Circuit Operation
  9. 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 CFF Selection
        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 External UVLO
        9. 9.2.2.9 Maximum Ambient Temperature
      3. 9.2.3 Application Curves
      4. 9.2.4 EMI Performance Curves
    3. 9.3 What to Do and What Not to Do
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
      1. 11.1.1 Ground and Thermal Considerations
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Documentation Support
      1. 12.1.1 Related Documentation
    2. 12.2 接收文档更新通知
    3. 12.3 支持资源
    4. 12.4 Trademarks
    5. 12.5 Electrostatic Discharge Caution
    6. 12.6 术语表
  13. 13Mechanical, Packaging, and Orderable Information

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8.4.3 Dropout Operation

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 level approaches the output voltage, the off-time of the high-side MOSFET starts to approach the minimum value (see Specifications). Beyond this point, the switching can become erratic and the output voltage can fall out of regulation. To avoid this problem, the LM63610-Q1 automatically reduces the switching frequency to increase the effective duty cycle and maintain regulation. There are two definitions of dropout voltage used in this data sheet. For both definitions, the dropout voltage is the difference between the input and output voltage under a specific condition. For the first definition, the difference is taken when the switching frequency has dropped to 1850 kHz (obviously this applies to cases where the nominal switching frequency is >1850 kHz). For this condition, the output voltage is within regulation. For the second definition, the difference is taken when the output voltage has fallen by 1% of the nominal regulation value. In this condition, the switching frequency has reached the lower limit of about 130 kHz. See Application Curves for details on these characteristics. Typical overall dropout characteristics can be found in Figure 8-9.

GUID-0C2A77DA-5155-4A3B-AB7A-E165CC3BF364-low.gifFigure 8-9 Overall Dropout Characteristic VOUT = 5 V, Refer to LM63615/25 Data Sheet