ZHCSJL1C September   2010  – April 2019 TPS61251

PRODUCTION DATA.  

  1. 1 特性
  2. 2 应用
  3. 3 说明
    1.     Device Images
      1.      简化原理图
  4. 4 修订历史记录
  5. 5 说明 （续）
  6. 6 Device Options
  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 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 Current Limit Operation
      2. 9.3.2 Soft Start
      3. 9.3.3 Enable
      4. 9.3.4 Undervoltage Lockout (UVLO)
      5. 9.3.5 Power Good
      6. 9.3.6 Input Overvoltage Protection
      7. 9.3.7 Load Disconnect and Reverse Current Protection
      8. 9.3.8 Thermal Regulation
      9. 9.3.9 Thermal Shutdown
    4. 9.4 Device Functional Modes
      1. 9.4.1 Power-Save Mode
      2. 9.4.2 Snooze Mode
      3. 9.4.3 100% Duty-Cycle Mode
  10. 10Application and Implementation
    1. 10.1 Application Information
    2. 10.2 Typical Application
      1. 10.2.1 Design Requirements
      2. 10.2.2 Detailed Design Procedure
        1. 10.2.2.1 Custom Design With WEBENCH® Tools
        2. 10.2.2.2 Output Voltage Setting
        3. 10.2.2.3 Average Input Current Limit
        4. 10.2.2.4 Maximum Output Current
        5. 10.2.2.5 Inductor Selection
        6. 10.2.2.6 Output Capacitor
        7. 10.2.2.7 Input Capacitor
        8. 10.2.2.8 Checking Loop Stability
      3. 10.2.3 Application Curves
  11. 11Power Supply Recommendations
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
    3. 12.3 Thermal Consideration
  13. 13器件和文档支持
    1. 13.1 器件支持
      1. 13.1.1 第三方产品免责声明
    2. 13.2 开发支持
      1. 13.2.1 使用 WEBENCH® 工具创建定制设计
    3. 13.3 接收文档更新通知
    4. 13.4 社区资源
    5. 13.5 商标
    6. 13.6 静电放电警告
    7. 13.7 术语表
  14. 14机械、封装和可订购信息

9.3.2 Soft Start

The TPS61251 device has an internal charging circuit that controls the current during the output capacitor charging and prevents the converter from inrush current that exceeds the set current limit. For typical 100 µs the current is ramped to the set current limit. After reaching the current limit threshold the output capacitor is charged with a constant current until the programmed output voltage is reached. During the phase where VIN > VOUT the rectifying switch is controlled by the current limit circuit and works as a linear regulator in constant current mode. If then VIN = VOUT, the converter starts switching and boosting up the voltage to its nominal output voltage by still charging the capacitor with a constant current set by resistor RILIM. During constant current charging power dissipation in the TPS61251 device is increased resulting in a thermal rise or heating of the device. If the output capacitor is very large charging time can be long and thermal rise high. To prevent overheating of the device during the charge phase the current will be limited to a lower value when device temperature is high. Please refer to Thermal Regulation.