SLUS774C AUGUST   2007  – December 2014

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3  Description
  4. 4 Revision History
  5. 5 Pin Configuration and 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  Voltage Reference
      2. 7.3.2  Oscillator
      3. 7.3.3  Input Undervoltage Lockout (UVLO) and Startup
      4. 7.3.4  Enable and Timed Turn On of the Outputs
      5. 7.3.5  Output Voltage Sequencing
      6. 7.3.6  Soft-Start
      7. 7.3.7  Output Voltage Regulation
      8. 7.3.8  Feedback Loop and Inductor-Capacitor (L-C) Filter Selection
      9. 7.3.9  Inductor-Capacitor (L-C) Selection
      10. 7.3.10 Maximum Output Capacitance
      11. 7.3.11 Minimum Output Capacitance
      12. 7.3.12 Modifying The Feedback Loop
        1. 7.3.12.1 Using High-ESR Output Capacitors
        2. 7.3.12.2 Using All Ceramic Output Capacitors
      13. 7.3.13 Example: TPS54386 Buck Converter Operating at 12-V Input, 3.3-V Output and 400-mA(P-P) Ripple Current
      14. 7.3.14 Bootstrap for the N-Channel MOSFET
      15. 7.3.15 Light Load Operation
      16. 7.3.16 SW Node Ringing
        1. 7.3.16.1 SW Node Snubber
        2. 7.3.16.2 Bootstrap Resistor
      17. 7.3.17 Output Overload Protection
      18. 7.3.18 Operating Near Maximum Duty Cycle
      19. 7.3.19 Dual Supply Operation
      20. 7.3.20 Cascading Supply Operation
      21. 7.3.21 Multiphase Operation
      22. 7.3.22 Bypass and FIltering
      23. 7.3.23 Overtemperature Protection and Junction Temperature Rise
      24. 7.3.24 Power Derating
    4. 7.4 Device Functional Modes
      1. 7.4.1 Minimum Input Voltage
      2. 7.4.2 ENx Control
  8. 8 Applications and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 12-V to 5-V and 3.3-V Converter
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1  Duty Cycle Estimation
          2. 8.2.1.2.2  Inductor Selection
          3. 8.2.1.2.3  Rectifier Diode Selection
          4. 8.2.1.2.4  Output Capacitor Selection
          5. 8.2.1.2.5  Voltage Setting
          6. 8.2.1.2.6  Compensation Capacitors
          7. 8.2.1.2.7  Input Capacitor Selection
          8. 8.2.1.2.8  Boot Strap Capacitor
          9. 8.2.1.2.9  ILIM
          10. 8.2.1.2.10 SEQ
          11. 8.2.1.2.11 Power Dissipation
        3. 8.2.1.3 Application Curves
      2. 8.2.2 24-V to 12-V and 24-V to 5-V
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
        3. 8.2.2.3 Application Curves
      3. 8.2.3 5-V to 3.3V and 5-V to 1.2 V
        1. 8.2.3.1 Design Requirements
        2. 8.2.3.2 Detailed Design Procedure
        3. 8.2.3.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
    3. 10.3 PowerPAD Package
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Definition of Symbols
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Related Links
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

9 Power Supply Recommendations

The TPS5438x is designed to operate from an input voltage supply range between 4.5 V and 28 V. This input supply should remain within the input voltage supply range. If the input supply is located more than a few inches from the TPS5438x converter bulk capacitance may be required in addition to the ceramic bypass capacitors. An electrolytic capacitor with a value of 100 μF is a typical choice.