ZHCS584B March   2011  – June 2019 LM21212-2

PRODUCTION DATA.  

  1. 1 特性
  2. 2 应用
  3. 3 说明
    1.     Device Images
      1.      简化应用电路
  4. 4 修订历史记录
  5. 5 说明（续）
  6. 6 Pin Configuration and Functions
    1.     Pin Descriptions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Ratings
    4. 7.4 Electrical Characteristics
    5. 7.5 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 Precision Enable
      2. 8.3.2 UVLO
      3. 8.3.3 Current Limit
      4. 8.3.4 Short-Circuit Protection
      5. 8.3.5 Thermal Protection
      6. 8.3.6 Power-Good Flag
      7. 8.3.7 Light Load Operation
    4. 8.4 Device Functional Modes
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Typical Application 1
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
          1. 9.2.1.2.1 Custom Design With WEBENCH® Tools
          2. 9.2.1.2.2 Output Voltage
          3. 9.2.1.2.3 Precision Enable
          4. 9.2.1.2.4 Soft Start
          5. 9.2.1.2.5 Resistor-Adjustable Frequency
          6. 9.2.1.2.6 Inductor Selection
          7. 9.2.1.2.7 Output Capacitor Selection
          8. 9.2.1.2.8 Input Capacitor Selection
          9. 9.2.1.2.9 Control Loop Compensation
        3. 9.2.1.3 Application Curves
      2. 9.2.2 Typical Application Schematic 2
        1. 9.2.2.1 Design Requirements
        2. 9.2.2.2 Detailed Design Procedure
  10. 10Layout
    1. 10.1 Layout Considerations
    2. 10.2 Layout Example
    3. 10.3 Thermal Considerations
  11. 11器件和文档支持
    1. 11.1 器件支持
      1. 11.1.1 第三方产品免责声明
      2. 11.1.2 开发支持
        1. 11.1.2.1 使用 WEBENCH® 工具创建定制设计
    2. 11.2 接收文档更新通知
    3. 11.3 社区资源
    4. 11.4 商标
    5. 11.5 静电放电警告
    6. 11.6 Glossary
  12. 12机械、封装和可订购信息

封装选项

机械数据 (封装 | 引脚)
散热焊盘机械数据 (封装 | 引脚)
订购信息

9.2.1.2.6 Inductor Selection

The inductor (L) used in the application will influence the ripple current and the efficiency of the system. The first selection criteria is to define a ripple current, ΔIL. In a buck converter, it is typically selected to run between 20% to 30% of the maximum output current. Figure 25 shows the ripple current in a standard buck converter operating in continuous conduction mode. Larger ripple current results in a smaller inductance value, which will lead to lower inductor series resistance, and improved efficiency. However, larger ripple current will also cause the device to operate in discontinuous conduction mode at a higher average output current.

LM21212-2 30155107.gifFigure 25. Switch And Inductor Current Waveforms

Once the ripple current has been determined, the appropriate inductor size can be calculated using the following equation:

Equation 6. LM21212-2 30155106.gif