SLVS839F July   2008  – October 2014 TPS54331


  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.  Custom Design with WEBENCH Tools
        2.  Switching Frequency
        3.  Output Voltage Set Point
        4.  Input Capacitors
        5.  Output Filter Components
          1. Inductor Selection
        6.  Capacitor Selection
        7.  Compensation Components
        8.  Bootstrap Capacitor
        9.  Catch Diode
        10. Output Voltage Limitations
        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


The TPS54331 device is a 28-V, 3-A, step-down (buck) converter with an integrated high-side n-channel MOSFET. To improve performance during line and load transients, the device implements a constant-frequency, current mode control which reduces output capacitance and simplifies external frequency compensation design. The TPS54331 device has a preset switching frequency of 570 kHz.

The TPS54331 device requires a minimum input voltage of 3.5 V for normal operation. The EN pin has an internal pullup current source that can adjust the input-voltage undervoltage lockout (UVLO) with two external resistors. In addition, the pullup current provides a default condition when the EN pin is floating for the device to operate. The operating current is 110 μA (typical) when not switching and under no load. When the device is disabled, the supply current is 1 μA (typical).

The integrated 80-mΩ high-side MOSFET allows for high-efficiency power-supply designs with continuous output currents up to 3 A.

The TPS54331 device reduces the external component count by integrating the boot recharge diode. The bias voltage for the integrated high-side MOSFET is supplied by an external capacitor on the BOOT to PH pin. The boot capacitor voltage is monitored by an UVLO circuit and turns the high-side MOSFET off when the voltage falls below a preset threshold of 2.1 V (typical). The output voltage can be stepped down to as low as the reference voltage.

By adding an external capacitor, the slow-start time of the TPS54331 device can be adjustable which enables flexible output filter selection.

To improve the efficiency at light load conditions, the TPS54331 device enters a special pulse skipping Eco-mode when the peak inductor current drops below 160 mA (typical).

The frequency foldback reduces the switching frequency during startup and overcurrent conditions to help control the inductor current. The thermal shutdown provides additional protection under fault conditions.