SLVS839F July   2008  – October 2014 TPS54331

PRODUCTION DATA.  

  1. Features
  2. Applications
  3. Description
  4. Simplified Schematic
    1.     TPS54331 (D Package) Efficiency
  5. Revision History
  6. Pin Configuration and Functions
    1.     Pin Functions
  7. Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 Handling Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Switching Characteristics
    7. 7.7 Typical Characteristics
  8. Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1  Fixed-Frequency PWM Control
      2. 8.3.2  Voltage Reference (Vref)
      3. 8.3.3  Bootstrap Voltage (BOOT)
      4. 8.3.4  Enable and Adjustable Input Undervoltage Lockout (VIN UVLO)
      5. 8.3.5  Programmable Slow Start Using SS Pin
      6. 8.3.6  Error Amplifier
      7. 8.3.7  Slope Compensation
      8. 8.3.8  Current-Mode Compensation Design
      9. 8.3.9  Overcurrent Protection and Frequency Shift
      10. 8.3.10 Overvoltage Transient Protection
      11. 8.3.11 Thermal Shutdown
    4. 8.4 Device Functional Modes
      1. 8.4.1 Eco-mode™
      2. 8.4.2 Operation With VIN < 3.5 V
      3. 8.4.3 Operation With EN Control
  9. Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1  Custom Design with WEBENCH Tools
        2. 9.2.2.2  Switching Frequency
        3. 9.2.2.3  Output Voltage Set Point
        4. 9.2.2.4  Input Capacitors
        5. 9.2.2.5  Output Filter Components
          1. 9.2.2.5.1 Inductor Selection
        6. 9.2.2.6  Capacitor Selection
        7. 9.2.2.7  Compensation Components
        8. 9.2.2.8  Bootstrap Capacitor
        9. 9.2.2.9  Catch Diode
        10. 9.2.2.10 Output Voltage Limitations
        11. 9.2.2.11 Power Dissipation Estimate
      3. 9.2.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
    3. 11.3 Electromagnetic Interference (EMI) Considerations
  12. 12Device and Documentation Support
    1. 12.1 Custom Design with WEBENCH Tools
    2. 12.2 Device Support
      1. 12.2.1 Development Support
    3. 12.3 Trademarks
    4. 12.4 Electrostatic Discharge Caution
    5. 12.5 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

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

Programmable Slow Start Using SS Pin

Programming the slow-start time externally is highly recommended because no slow-start time is implemented internally. The TPS54331 device effectively uses the lower voltage of the internal voltage reference or the SS pin voltage as the reference voltage of the power supply that is fed into the error amplifier and regulates the output accordingly. A capacitor (CSS) on the SS pin to ground implements a slow-start time. The TPS54331 device has an internal pullup current-source of 2 μA that charges the external slow-start capacitor. Use Equation 3 to calculate the slow-start time (10% to 90%).

Equation 3. TPS54331 q3_lvs839.gif

where

  • Vref = 0.8 V
  • ISS = 2 μA

The slow-start time should be set between 1 ms to 10 ms to ensure good startup behavior. The value of the slow-start capacitor should not exceed 27 nF.

During normal operation, the TPS54331 device stops switching if the input voltage drops below the VIN UVLO threshold, the EN pin is pulled below 1.25 V, or a thermal shutdown event occurs.