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

8.2.3.8 Output Voltage And Feedback Resistors Selection

For the example design, 20.0 kΩ was selected for R6. Using Equation 31, R7 is calculated as 10.0 kΩ.

Equation 31. GUID-26687A1E-EB28-4A2D-B2A4-6627C1ECC266-low.gif

Due to the internal design of the TPS54719, there is a minimum output voltage limit for any given input voltage. The output voltage can never be lower than the internal voltage reference of 0.6 V. Above 0.6 V, the output voltage may be limited by the minimum controllable on time. The minimum output voltage in this case is given by Equation 32.

Equation 32. GUID-793E32E8-4127-41E4-875A-E2D8235FE248-low.gif

where:

  • VOUT(MIN) = minimum achievable output voltage
  • tON = minimum controllable on time (64 ns - 100 nsec typical)
  • tS = 1/fSW (switching frequency)
  • tDEAD = dead time (70 nsec typical)
  • VIN = maximum input voltage
  • RDS = minimum high side MOSFET on resistance (26 - 35 mΩ)
  • IOUT = minimum load current
  • RL = series resistance of output inductor

There is also a maximum achievable output voltage which is limited by the minimum off time. The maximum output voltage is given by Equation 33

Equation 33. GUID-4E7B7F2D-9632-4E93-9215-142A59FAC285-low.gif

where:

  • VOUT(MAX) = maximum achievable output voltage
  • tS = 1/fSW (switching frequency)
  • tOFF = minimum off time (0 nsec typical)
  • tDEAD = dead time (70 nsec typical)
  • VIN = minimum input voltage
  • IOUT = maximum load current
  • RDS = maximum high side MOSFET on resistance (60 - 70 mΩ)
  • RL = series resistance of output inductor