JAJSMS4F August   2021  – March 2024 TPS7H2211-SEP , TPS7H2211-SP

PRODUCTION DATA  

  1.   1
  2. 1 特長
  3. 2 アプリケーション
  4. 3 概要
  5. 4 Device Options
  6. 5 Related Products
  7. 6 Pin Configuration and Functions
  8. 7 Specifications
    1. 7.1  Absolute Maximum Ratings
    2. 7.2  ESD Ratings
    3. 7.3  Recommended Operating Conditions
    4. 7.4  Thermal Information
    5. 7.5  Electrical Characteristics: All Devices
    6. 7.6  Electrical Characteristics: CFP and KGD Options
    7. 7.7  Electrical Characteristics: HTSSOP Option
    8. 7.8  Switching Characteristics: All Devices
    9. 7.9  Quality Conformance Inspection
    10. 7.10 Typical Characteristics
  9. 8 Parameter Measurement Information
  10. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1 Enable and Overvoltage Protection
      2. 9.3.2 Current Limit
      3. 9.3.3 Soft Start (Adjustable Rise Time)
      4. 9.3.4 Parallel Operation
      5. 9.3.5 Reverse Current Protection
      6. 9.3.6 Forward Leakage Current
    4. 9.4 Device Functional Modes
  11. 10Application and Implementation
    1. 10.1 Application Information
    2. 10.2 Typical Applications
      1. 10.2.1 Application 1: Cold Sparing
        1. 10.2.1.1 Design Requirements
        2. 10.2.1.2 Detailed Design Procedure
          1. 10.2.1.2.1 Capacitance
          2. 10.2.1.2.2 Enable Control
          3. 10.2.1.2.3 Overvoltage Protection
          4. 10.2.1.2.4 Soft Start Time
          5. 10.2.1.2.5 Summary
        3. 10.2.1.3 Application Curve
      2. 10.2.2 Application 2: Protection
        1. 10.2.2.1 Design Requirements
        2. 10.2.2.2 Detailed Design Procedure
          1. 10.2.2.2.1 Capacitance
          2. 10.2.2.2.2 Enable Control
          3. 10.2.2.2.3 Overvoltage Protection
          4. 10.2.2.2.4 Soft Start Time
          5. 10.2.2.2.5 Summary
        3. 10.2.2.3 Application Curve
    3. 10.3 Power Supply Recommendations
    4. 10.4 Layout
      1. 10.4.1 Layout Guidelines
      2. 10.4.2 Layout Example
  12. 11Device and Documentation Support
    1. 11.1 Documentation Support
      1. 11.1.1 Related Documentation
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 サポート・リソース
    4. 11.4 Trademarks
    5. 11.5 静電気放電に関する注意事項
    6. 11.6 用語集
  13. 12Revision History
  14. 13Mechanical, Packaging, and Orderable Information
10.2.1.2.4 Soft Start Time

The desired 10-ms soft start time is achieved following the procedure in Section 9.3.3. The procedure is replicated below for convenience.

First, use Equation 13 to determine the needed value of CSS. This results in a calculated CSS value of 67.7 nF. A 68-nF ±10% capacitor is selected.

Equation 13. GUID-B21EA23D-FD64-4031-947E-AC66D842340C-low.png

where

  • tSS = 10 ms = 10 × 10–3 s
  • ISS(TYP) = 65 μA = 65 × 10–6 A
  • VOUT(NOM) = 12 V

Next determine the resulting slew rate using Equation 14. Using the minimum value for the 10% tolerance CSS and the maximum value for ISS results in the worst case (fastest) slew rate of 1,356 V/s.

Equation 14. GUID-7D22E873-5513-4D53-9596-EDB78DBC3023-low.png

where

  • ISS(MAX) = 83 μA = 83 × 10–6 A
  • CSS = 68 nF × (1 – 10%) = 61.2 × 10–9 F

Finally, determine if the resulting slew rate is less than the maximum allowed by Equation 15. IL_trip is typically 8.5 A, but in order to select a conservative value it is suggested to let IL_trip = 5.4 A (which is also the absolute maximum rating for continuous switch current). The 1,356-V/s slew rate is less than the maximum acceptable slew rate of 14,109 V/s. Therefore, this soft start capacitor is acceptable.

Equation 15. GUID-88D3220D-0BD4-4A0E-B3F6-2DC1447446D0-low.png

where

  • IL_trip = 5.4 A
  • IOUT(NOM) = 3.0 A
  • COUT = 170.1 μF = 170.1 × 10–6 F

While it is typically trivial to meet the slew rate restrictions, note that for space applications a large output capacitor is often utilized. This results in a lower maximum acceptable slew rate and additional care must be taken in order to ensure the expected slew rate is not too fast.