JAJSBM7C September   2011  – October 2017 TPS54623

PRODUCTION DATA.  

  1. 1 特長
  2. 2 アプリケーション
  3. 3 概要
    1.     効率と負荷電流との関係
  4. 4 改訂履歴
  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  VIN and Power VIN Pins (VIN and PVIN)
      2. 7.3.2  Voltage Reference
      3. 7.3.3  Adjusting the Output Voltage
      4. 7.3.4  Safe Start-up into Pre-Biased Outputs
      5. 7.3.5  Error Amplifier
      6. 7.3.6  Slope Compensation
      7. 7.3.7  Enable and Adjusting Undervoltage Lockout
      8. 7.3.8  Slow Start (SS/TR)
      9. 7.3.9  Power Good (PWRGD)
      10. 7.3.10 Bootstrap Voltage (BOOT) and Low Dropout Operation
      11. 7.3.11 Sequencing (SS/TR)
      12. 7.3.12 Output Overvoltage Protection (OVP)
      13. 7.3.13 Overcurrent Protection
        1. 7.3.13.1 High-side MOSFET Overcurrent Protection
        2. 7.3.13.2 Low-side MOSFET Overcurrent Protection
      14. 7.3.14 Thermal Shutdown
      15. 7.3.15 Small Signal Model for Loop Response
      16. 7.3.16 Simple Small Signal Model for Peak Current Mode Control
      17. 7.3.17 Small Signal Model for Frequency Compensation
    4. 7.4 Device Functional Modes
      1. 7.4.1 Fixed Frequency PWM Control
      2. 7.4.2 Continuous Current Mode Operation (CCM)
      3. 7.4.3 Light Load Efficiency Operation
      4. 7.4.4 Adjustable Switching Frequency and Synchronization (RT/CLK)
        1. 7.4.4.1 Adjustable Switching Frequency (RT Mode)
        2. 7.4.4.2 Synchronization (CLK mode)
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Fast Transient Considerations
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1  Custom Design With WEBENCH® Tools
        2. 8.2.2.2  Operating Frequency
        3. 8.2.2.3  Output Inductor Selection
        4. 8.2.2.4  Output Capacitor Selection
        5. 8.2.2.5  Input Capacitor Selection
        6. 8.2.2.6  Slow Start Capacitor Selection
        7. 8.2.2.7  Bootstrap Capacitor Selection
        8. 8.2.2.8  Under Voltage Lockout Set Point
        9. 8.2.2.9  Output Voltage Feedback Resistor Selection
          1. 8.2.2.9.1 Minimum Output Voltage
        10. 8.2.2.10 Compensation Component Selection
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 Estimated Circuit Area
    2. 10.2 Layout Examples
  11. 11デバイスおよびドキュメントのサポート
    1. 11.1 デバイス・サポート
      1. 11.1.1 デベロッパー・ネットワークの製品に関する免責事項
      2. 11.1.2 開発サポート
      3. 11.1.3 WEBENCH®ツールによるカスタム設計
    2. 11.2 ドキュメントのサポート
      1. 11.2.1 関連資料
    3. 11.3 ドキュメントの更新通知を受け取る方法
    4. 11.4 コミュニティ・リソース
    5. 11.5 商標
    6. 11.6 静電気放電に関する注意事項
    7. 11.7 Glossary
  12. 12メカニカル、パッケージ、および注文情報

7.3.8 Slow Start (SS/TR)

The device uses the lower voltage of the internal voltage reference or the SS/TR pin voltage as the reference voltage and regulates the output accordingly. A capacitor on the SS/TR pin to ground implements a slow start time. The device has an internal pullup current source of 2.3 μA that charges the external slow start capacitor. The calculations for the slow start time (Tss, 10% to 90%) and slow start capacitor (Css) are shown in Equation 4. The voltage reference (Vref) is 0.6 V and the slow start charge current (Iss) is 2.3 μA.

Equation 4. TPS54623 eq4_tss_lvs949.gif

When the input UVLO is triggered, the EN pin is pulled below 1.21 V, or a thermal shutdown event occurs the device stops switching and enters low current operation. At the subsequent power up, when the shutdown condition is removed, the device does not start switching until it has discharged its SS/TR pin to ground ensuring proper soft start behavior.