SLVSFL4 June   2020 TPS2124

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Typical Application
  4. 4 Revision History
  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 Parameter Measurement Information
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Input Settling Time and Output Soft Start Control (SS)
        1. 8.3.1.1 Slew Rate vs. CSS Capacitor
      2. 8.3.2 Active Current Limiting (ILM)
      3. 8.3.3 Short-Circuit Protection
      4. 8.3.4 Thermal Protection (TSD)
      5. 8.3.5 Over-voltage Protection (OVx)
      6. 8.3.6 Fast Reverse Current Blocking (RCB)
      7. 8.3.7 Input Voltage Comparator (VCOMP)
    4. 8.4 TPS2124 Device Functional Modes
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Manual Switchover Schematic
      2. 9.2.2 Design Requirements
      3. 9.2.3 Detailed Design Description
      4. 9.2.4 Design Procedure
        1. 9.2.4.1 Selecting OVx Resistors
        2. 9.2.4.2 Selecting Soft-Start Capacitor and Current Limit Resistors
      5. 9.2.5 Application Curves
    3. 9.3 Highest Voltage Operation (VCOMP)
      1. 9.3.1 Application Schematic
      2. 9.3.2 Design Requirements
      3. 9.3.3 Detailed Design Description
      4. 9.3.4 Detailed Design Procedure
      5. 9.3.5 Application Curves
    4. 9.4 Reverse Polarity Protection with TPS2124
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Receiving Notification of Documentation Updates
    2. 12.2 Support Resources
    3. 12.3 Trademarks
    4. 12.4 Electrostatic Discharge Caution
    5. 12.5 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

9.2.4.2 Selecting Soft-Start Capacitor and Current Limit Resistors

Equation 1 can be used to determine the RLIM values for this application. In this example, the DC load current is 1 A. Setting the current limit to 2 A will limit potential inrush current events and protect downstream loads. See Equation 4 for the TPS2124 ILM Calculation:

Equation 4. TPS2124 slvsea3-equation-8.gif

To calculate the slew rate needed to limit the inrush current to 100 mA, the Slew Rate Calculation can be used in Equation 5:

Equation 5. TPS2124 slvsea3-slew-rate-calculation.gif
Equation 6. TPS2124 slvsea3-slew-rate-calculation-2.gif

Using this equation, the slew rate must be limited to 1000V/S or below to keep the inrush current below 100 mA. According to Table 1, at 5 V a CSS capacitance of 100 nF will provide a slew rate of 780V/S (typical), which is below the calculated threshold of 1000V/S. Therefore, a 100 nF capacitor will limit the inrush below 100 mA in a typical application.