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

8.2.3.7 Undervoltage Lockout Set Point

The Undervoltage Lockout (UVLO) can be adjusted using an external voltage divider on the EN pin of the TPS54719. The UVLO has two thresholds: one for power up when the input voltage is rising and one for power down or brown outs when the input voltage is falling. For the example design, the supply should turn on and start switching once the input voltage increases above 2.794 V (VSTART). After the regulator starts switching, it should continue to do so until the input voltage falls below 2.595 V (VSTOP).

The programmable UVLO and enable voltages are set using a resistor divider between Vin and ground to the EN pin. Equation 2 and Equation 3 can be used to calculate the resistance values necessary. From Equation 2 and Equation 3, a 14.3 kΩ between VIN and EN and a 11.5 kΩ between EN and ground are required to produce the 2.794 and 2.595 volt start and stop voltages.