SLVS839H July   2008  – October 2023 TPS54331

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Revision History
  6. 5 Pin Configuration and Functions
  7. 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 Switching Characteristics
    7. 6.7 Typical Characteristics
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Fixed-Frequency PWM Control
      2. 7.3.2  Voltage Reference (VREF)
      3. 7.3.3  Bootstrap Voltage (BOOT)
      4. 7.3.4  Enable and Adjustable Input Undervoltage Lockout (VIN UVLO)
      5. 7.3.5  Programmable Slow Start Using SS Pin
      6. 7.3.6  Error Amplifier
      7. 7.3.7  Slope Compensation
      8. 7.3.8  Current-Mode Compensation Design
      9. 7.3.9  Overcurrent Protection and Frequency Shift
      10. 7.3.10 Overvoltage Transient Protection
      11. 7.3.11 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 Eco-mode
      2. 7.4.2 Operation With VIN < 3.5 V
      3. 7.4.3 Operation With EN Control
  9. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1  Custom Design with WEBENCH® Tools
        2. 8.2.2.2  Switching Frequency
        3. 8.2.2.3  Output Voltage Set-Point
        4. 8.2.2.4  Input Capacitors
        5. 8.2.2.5  Output Filter Components
          1. 8.2.2.5.1 Inductor Selection
        6. 8.2.2.6  Capacitor Selection
        7. 8.2.2.7  Compensation Components
        8. 8.2.2.8  Bootstrap Capacitor
        9. 8.2.2.9  Catch Diode
        10. 8.2.2.10 Output Voltage Limitations
        11. 8.2.2.11 Power Dissipation Estimate
      3. 8.2.3 Application Curves
    3. 8.3 Power Supply Recommendations
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
      2. 8.4.2 Layout Example
      3. 8.4.3 Electromagnetic Interference (EMI) Considerations
  10. 9 Device and Documentation Support
    1. 9.1 Device Support
      1. 9.1.1 Development Support
        1. 9.1.1.1 Custom Design with WEBENCH® Tools
    2. 9.2 Support Resources
    3. 9.3 Receiving Notification of Documentation Updates
    4. 9.4 Trademarks
    5. 9.5 Electrostatic Discharge Caution
    6. 9.6 Glossary
  11. 10Mechanical, Packaging, and Orderable Information

7.3.9 Overcurrent Protection and Frequency Shift

The TPS54331 device implements current mode control that uses the COMP pin voltage to turn off the high-side MOSFET on a cycle-by-cycle basis. During each cycle, the switch current and the COMP pin voltage are compared. When the peak inductor current intersects the COMP pin voltage, the high-side switch is turned off. During overcurrent conditions that pull the output voltage low, the error amplifier responds by driving the COMP pin high, causing the switch current to increase. The COMP pin has a maximum clamp internally, which limits the output current.

The TPS54331 device provides robust protection during short circuits. Overcurrent runaway is possible in the output inductor during a short circuit at the output. The TPS54331 device solves this issue by increasing the off time during short-circuit conditions by lowering the switching frequency. The switching frequency is divided by 1, 2, 4, and 8 as the voltage ramps from 0 to 0.8 V on VSENSE pin. The relationship between the switching frequency and the VSENSE pin voltage is listed in Table 7-2.

Table 7-2 Switching Frequency Conditions
Switching FrequencyVSENSE Pin Voltage
570 kHzVSENSE ≥ 0.6 V
570 kHz / 20.6 V > VSENSE ≥ 0.4 V
570 kHz / 40.4 V > VSENSE ≥ 0.2 V
570 kHz / 80.2 V > VSENSE