JAJSR60F August   2008  – June 2020 TPS40210-Q1 , TPS40211-Q1

PRODUCTION DATA  

  1.   1
  2. 1 特長
  3. 2 アプリケーション
  4. 3 概要
  5.   5
  6. 4 Revision History
  7. 5 Pin Configuration and Functions
    1.     Pin Functions
  8. 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 Timing Requirements
    7. 6.7 Switching Characteristics
    8. 6.8 Typical Characteristics
  9. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Minimum On-Time and Off-Time Considerations
      2. 7.3.2  Current Sense and Overcurrent
      3. 7.3.3  Current Sense and Subharmonic Instability
      4. 7.3.4  Current Sense Filtering
      5. 7.3.5  Soft Start
      6. 7.3.6  BP Regulator
      7. 7.3.7  Shutdown (DIS/ EN Pin)
      8. 7.3.8  Control Loop Considerations
      9. 7.3.9  Gate Drive Circuit
      10. 7.3.10 TPS40211-Q1
    4. 7.4 Device Functional Modes
      1. 7.4.1 Setting the Oscillator Frequency
      2. 7.4.2 Synchronizing the Oscillator
  10. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1  Duty Cycle Estimation
        2. 8.2.2.2  Inductor Selection
        3. 8.2.2.3  Rectifier Diode Selection
        4. 8.2.2.4  Output Capacitor Selection
        5. 8.2.2.5  Input Capacitor Selection
        6. 8.2.2.6  Current Sense and Current Limit
        7. 8.2.2.7  Current Sense Filter
        8. 8.2.2.8  Switching MOSFET Selection
        9. 8.2.2.9  Feedback Divider Resistors
        10. 8.2.2.10 Error Amplifier Compensation
        11. 8.2.2.11 R-C Oscillator
        12. 8.2.2.12 Soft-Start Capacitor
        13. 8.2.2.13 Regulator Bypass
      3. 8.2.3 Application Curves
  11. 9 Power Supply Recommendations
  12. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  13. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 サード・パーティ製品に関する免責事項
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Related Links
    4. 11.4 ドキュメントの更新通知を受け取る方法
    5. 11.5 サポート・リソース
    6. 11.6 Trademarks
    7. 11.7 静電気放電に関する注意事項
    8. 11.8 用語集
  14. 12Mechanical, Packaging, and Orderable Information
    1.     70

7.3.4 Current Sense Filtering

In most cases, a small filter placed on the ISNS pin improves performance of the converter. These are the components RIFLT and CIFLT in Figure 7-2. The time constant of this filter should be approximately 10% of the nominal pulse width of the converter. The pulse width can be found using Equation 10.

Equation 10. GUID-2E0886E0-4BD6-43E8-BFF3-B774A3934148-low.gif

The suggested time constant is then

Equation 11. GUID-2AF386F6-C6D1-42FD-B76D-156114AB891A-low.gif

The range of RIFLT should be from about 1 kΩ to 5 kΩ for best results. Higher values can be used, but this raises the impedance of the ISNS pin connection more than necessary and can lead to noise-pickup issues in some layouts. CISNS should be located as close as possible to the ISNS pin as well to provide noise immunity.