ZHCSF14D March   2010  – October 2018 TPS54260

PRODUCTION DATA.  

  1. 1 特性
  2. 2 应用
  3. 3 说明
    1.     Device Images
      1.      简化原理图
      2.      效率与负载电流间的关系
  4. 4 修订历史记录
  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 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 PWM Control
      2. 7.3.2  Slope Compensation Output Current
      3. 7.3.3  Pulse-Skip Eco-Mode
      4. 7.3.4  Low-Dropout Operation and Bootstrap Voltage (BOOT)
      5. 7.3.5  Error Amplifier
      6. 7.3.6  Voltage Reference
      7. 7.3.7  Adjusting the Output Voltage
      8. 7.3.8  Enable and Adjusting Undervoltage Lockout
      9. 7.3.9  Slow-Start / Tracking Pin (SS/TR)
      10. 7.3.10 Overload Recovery Circuit
      11. 7.3.11 Sequencing
      12. 7.3.12 Constant Switching Frequency and Timing Resistor (RT/CLK Pin)
      13. 7.3.13 Overcurrent Protection and Frequency Shift
      14. 7.3.14 Selecting the Switching Frequency
      15. 7.3.15 How to Interface to RT/CLK Pin
      16. 7.3.16 Powergood (PWRGD Pin)
      17. 7.3.17 Overvoltage Transient Protection
      18. 7.3.18 Thermal Shutdown
      19. 7.3.19 Small Signal Model for Loop Response
      20. 7.3.20 Simple Small Signal Model for Peak Current Mode Control
      21. 7.3.21 Small Signal Model for Frequency Compensation
    4. 7.4 Device Functional Modes
      1. 7.4.1 Operation Near Minimum Input Voltage
      2. 7.4.2 Operation With Enable Control
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 3.3-V Output Application
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1  Custom Design With WEBENCH® Tools
          2. 8.2.1.2.2  Selecting the Switching Frequency
          3. 8.2.1.2.3  Output Inductor Selection (LO)
          4. 8.2.1.2.4  Output Capacitor
          5. 8.2.1.2.5  Catch Diode
          6. 8.2.1.2.6  Input Capacitor
          7. 8.2.1.2.7  Slow-Start Capacitor
          8. 8.2.1.2.8  Bootstrap Capacitor Selection
          9. 8.2.1.2.9  Undervoltage Lock Out Set Point
          10. 8.2.1.2.10 Output Voltage and Feedback Resistors Selection
          11. 8.2.1.2.11 Compensation
          12. 8.2.1.2.12 Discontinuous Mode and Eco-Mode Boundary
          13. 8.2.1.2.13 Power Dissipation Estimate
        3. 8.2.1.3 Application Curves
      2. 8.2.2 Inverting Power Supply
      3. 8.2.3 Split-Rail Power Supply
      4. 8.2.4 12-V to 3.8-V GSM Power Supply
      5. 8.2.5 24-V to 4.2-V GSM Power Supply
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  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 术语表
  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

8.2.1.2.7 Slow-Start Capacitor

The slow-start capacitor determines the minimum amount of time it will take for the output voltage to reach its nominal programmed value during power-up. This is useful if a load requires a controlled voltage slew rate. This is also used if the output capacitance is large and would require large amounts of current to quickly charge the capacitor to the output voltage level. The large currents necessary to charge the capacitor may make the TPS54260 reach the current limit or excessive current draw from the input power supply may cause the input voltage rail to sag. Limiting the output voltage slew rate solves both of these problems.

The slow-start time must be long enough to allow the regulator to charge the output capacitor up to the output voltage without drawing excessive current. Equation 40 can be used to find the minimum slow-start time, tss, necessary to charge the output capacitor, Cout, from 10% to 90% of the output voltage, Vout, with an average slow-start current of Issavg. In the example, to charge the effective output capacitance of 72.4 µF up to 3.3 V while only allowing the average output current to be 1 A would require a 0.19-ms slow-start time.

Once the slow-start time is known, the slow-start capacitor value can be calculated using Equation 6. For the example circuit, the slow-start time is not too critical since the output capacitor value is 2 x 47 μF which does not require much current to charge to 3.3 V. The example circuit has the slow-start time set to an arbitrary value of 3.5 ms which requires a 8.75-nF slow-start capacitor. For this design, the next larger standard value of 10 nF is used.

Equation 40. TPS54260 eq42_lvs795.gif