SLUSF22B November   2024  – March 2025 TPS54338 , TPS54438 , TPS54538

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information
    5. 5.5 Electrical Characteristics
    6. 5.6 Typical Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1  Fixed Frequency Peak Current Mode
      2. 6.3.2  Mode Selection
      3. 6.3.3  Voltage Reference
      4. 6.3.4  Output Voltage Setting
      5. 6.3.5  Switching Frequency Selection / Synchronization
      6. 6.3.6  Phase Shift
      7. 6.3.7  Enable and Adjusting Undervoltage Lockout
      8. 6.3.8  External Soft Start and Prebiased Soft Start
      9. 6.3.9  Power Good
      10. 6.3.10 Minimum On Time, Minimum Off Time, and Frequency Foldback
      11. 6.3.11 Frequency Spread Spectrum
      12. 6.3.12 Overvoltage Protection
      13. 6.3.13 Overcurrent and Undervoltage Protection
      14. 6.3.14 Thermal Shutdown
    4. 6.4 Device Functional Modes
      1. 6.4.1 Modes Overview
      2. 6.4.2 Heavy Load Operation
      3. 6.4.3 Pulse Frequency Modulation
      4. 6.4.4 Forced Continuous Conduction Modulation
      5. 6.4.5 Dropout Operation
      6. 6.4.6 Minimum On-Time Operation
      7. 6.4.7 Shutdown Mode
  8. 7 Application and Implementation
    1. 7.1 Application Information
    2. 7.2 Typical Application
      1. 7.2.1 Design Requirements
      2. 7.2.2 Detailed Design Procedure
        1. 7.2.2.1 Custom Design With WEBENCH® Tools
        2. 7.2.2.2 Output Voltage Resistors Selection
        3. 7.2.2.3 Choosing Switching Frequency
        4. 7.2.2.4 Soft-Start Capacitor Selection
        5. 7.2.2.5 Output Inductor Selection
        6. 7.2.2.6 Output Capacitor Selection
        7. 7.2.2.7 Input Capacitor Selection
        8. 7.2.2.8 Feedforward Capacitor CFF Selection
        9. 7.2.2.9 Maximum Ambient Temperature
      3. 7.2.3 Application Curves
    3. 7.3 Best Design Practices
    4. 7.4 Power Supply Recommendations
    5. 7.5 Layout
      1. 7.5.1 Layout Guidelines
      2. 7.5.2 Layout Example
  9. 8 Device and Documentation Support
    1. 8.1 Device Support
      1. 8.1.1 Third-Party Products Disclaimer
      2. 8.1.2 Development Support
        1. 8.1.2.1 Custom Design With WEBENCH® Tools
    2. 8.2 Documentation Support
      1. 8.2.1 Related Documentation
    3. 8.3 Receiving Notification of Documentation Updates
    4. 8.4 Support Resources
    5. 8.5 Trademarks
    6. 8.6 Electrostatic Discharge Caution
    7. 8.7 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

6.3.2 Mode Selection

With different configuration of the MODE pin, the device is featured with selectable PFM/FCCM at light load, adjustable soft-start time function / power-good indicator function for the SS/PG pin, and user-selectable spread spectrum feature for EMI enhancement. The following table shows different MODE pin configurations. TI recommends using 1% tolerance resistors with a low temperature coefficient for MODE selection.

Table 6-1 MODE Pin Configuration Table
Device Recommended Mode Resistor / kΩ Operation in Light Load Function of SS/PG Pin Frequency Spread Spectrum Fss
TPS54538 < 4kΩ / short PFM SS Yes
TPS54x38 18kΩ PFM PG Yes
TPS54x38 180kΩ FCCM SS Yes
TPS54x38 330kΩ FCCM PG Yes
TPS54x38 680kΩ FCCM SS No
TPS54x38 > 1.3MΩ / floating FCCM PG No