SLVSBF3B June   2012  – May 2019 TPS54678

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Simplified Schematic
      2.      Efficiency vs Output Current
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin 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  Fixed Frequency PWM Control
      2. 7.3.2  Slope Compensation and Output Current
      3. 7.3.3  Bootstrap Voltage (Boot) and Low Dropout Operation
      4. 7.3.4  Error Amplifier
      5. 7.3.5  Voltage Reference
      6. 7.3.6  Adjusting the Output Voltage
      7. 7.3.7  Enable and Adjusting Undervoltage Lockout
      8. 7.3.8  Soft-Start Pin
      9. 7.3.9  Sequencing
      10. 7.3.10 Constant Switching Frequency and Timing Resistor (RT/CLK Pin)
      11. 7.3.11 Overcurrent Protection
        1. 7.3.11.1 High-Side Overcurrent Protection
        2. 7.3.11.2 Low-Side Overcurrent Protection
      12. 7.3.12 Safe Start-Up into Prebiased Outputs
      13. 7.3.13 Synchronize Using the RT/CLK Pin
      14. 7.3.14 Power Good (PWRGD Pin)
      15. 7.3.15 Overvoltage Transient Protection
      16. 7.3.16 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 Small Signal Model for Loop Response
      2. 7.4.2 Simple Small Signal Model for Peak Current Mode Control
      3. 7.4.3 Small Signal Model for Frequency Compensation
  8. 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 Step One: Select the Switching Frequency
        3. 8.2.2.3 Step Two: Select the Output Inductor
        4. 8.2.2.4 Step Three: Choose the Output Capacitor
        5. 8.2.2.5 Step Four: Select the Input Capacitor
        6. 8.2.2.6 Step Five: Choose the Soft-Start Capacitor
        7. 8.2.2.7 Step Six: Select the Bootstrap Capacitor
        8. 8.2.2.8 Step Eight: Select Output Voltage and Feedback Resistors
          1. 8.2.2.8.1 Output Voltage Limitations
        9. 8.2.2.9 Step Nine: Select Loop Compensation Components
      3. 8.2.3 Application Curves
        1. 8.2.3.1 Additional Information About Application Curves
          1. 8.2.3.1.1 Efficiency
          2. 8.2.3.1.2 Voltage Ripple Measurements
          3. 8.2.3.1.3 Start-Up and Shutdown Waveforms
          4. 8.2.3.1.4 Hiccup Mode Current Limit
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
    3. 10.3 Power Dissipation Estimate
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
      2. 11.1.2 Development Support
        1. 11.1.2.1 Custom Design With WEBENCH® Tools
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Receiving Notification of Documentation Updates
    4. 11.4 Community Resources
    5. 11.5 Trademarks
    6. 11.6 Electrostatic Discharge Caution
    7. 11.7 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

7.3.11.2 Low-Side Overcurrent Protection

The conduction current of the low-side MOSFET is also monitored by TPS54678. During normal operation, the low-side sources current into the load. When the sourcing current reaches the internally set low-side sourcing (forward) current limit, the high-side is not turned on and skipped during the next clock cycle. Under this condition, the low-side is kept on until the sourcing current becomes less than the internally set current limit and then the high-side is turned on at the beginning of the following clock cycle. This ensures protection under an output short condition; thereby, preventing current run-away.

The low-side can also sink current from the load. If the low-side sinking (reverse) current limit is exceeded, the low-side is turned off immediately for the rest of the clock cycle. Under this condition, both the high-side and low-side are off until the start of the next cycle.