SLVSB69C June   2012  – September 2021 TPS54719

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and 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 Timing Requirements
    7. 6.7 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 Slow Start/Tracking Pin
      9. 7.3.9 Sequencing
    4. 7.4 Device Functional Modes
      1. 7.4.1  Constant Switching Frequency And Timing Resistor (RT Pin)
      2. 7.4.2  Overcurrent Protection
      3. 7.4.3  Frequency Shift
      4. 7.4.4  Reverse Overcurrent Protection
      5. 7.4.5  Power Good (PWRGD Pin)
      6. 7.4.6  Overvoltage Transient Protection
      7. 7.4.7  Thermal Shutdown
      8. 7.4.8  Small Signal Model For Loop Response
      9. 7.4.9  Simple Small Signal Model For Peak Current Mode Control
      10. 7.4.10 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 High Frequency, 1.8-V Output Power Supply Design With Adjusted UVLO
      2. 8.2.2 Design Requirements
      3. 8.2.3 Detailed Design Procedure
        1. 8.2.3.1 Selecting The Switching Frequency
        2. 8.2.3.2 Output Inductor Selection
        3. 8.2.3.3 Output Capacitor
        4. 8.2.3.4 Input Capacitor
        5. 8.2.3.5 Slow-Start Capacitor
        6. 8.2.3.6 Bootstrap Capacitor Selection
        7. 8.2.3.7 Undervoltage Lockout Set Point
        8. 8.2.3.8 Output Voltage And Feedback Resistors Selection
        9. 8.2.3.9 Compensation
      4. 8.2.4 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
      1. 10.2.1 Power Dissipation Estimate
  11. 11Device and Documentation Support
    1. 11.1 Receiving Notification of Documentation Updates
    2. 11.2 Support Resources
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

7.4.3 Frequency Shift

To operate at high switching frequencies and provide protection during overcurrent conditions, the TPS54719 implements a frequency shift. If frequency shift was not implemented, during an overcurrent condition, the low-side MOSFET may not be turned off long enough to reduce the current in the inductor, causing a current runaway. With frequency shift, during an overcurrent condition, the switching frequency is reduced from 100%, then 50%, then 25% as the voltage decreases from 0.6 to 0 volts on VSENSE pin to allow the low-side MOSFET to be off long enough to decrease the current in the inductor. During start-up, the switching frequency increases as the voltage on VSENSE increases from 0 to 0.6 volts. See Figure 6-13 for details.