SLVSDC9B November   2016  – November 2019 TPS54824

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
    1.     Simplified Schematic
  3. 3 Description
    1.     Efficiency
  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 Switching Characteristics
    7. 6.7 Timing Requirements
    8. 6.8 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  Continuous Conduction Mode Operation (CCM)
      3. 7.3.3  VIN Pins and VIN UVLO
      4. 7.3.4  Voltage Reference and Adjusting the Output Voltage
      5. 7.3.5  Error Amplifier
      6. 7.3.6  Enable and Adjustable UVLO
      7. 7.3.7  Soft Start and Tracking
      8. 7.3.8  Safe Start-up into Pre-Biased Outputs
      9. 7.3.9  Power Good
      10. 7.3.10 Sequencing (SS/TRK)
      11. 7.3.11 Adjustable Switching Frequency (RT Mode)
      12. 7.3.12 Synchronization (CLK Mode)
      13. 7.3.13 Bootstrap Voltage and 100% Duty Cycle Operation (BOOT)
      14. 7.3.14 Output Overvoltage Protection (OVP)
      15. 7.3.15 Overcurrent Protection
        1. 7.3.15.1 High-side MOSFET Overcurrent Protection
        2. 7.3.15.2 Low-side MOSFET Overcurrent Protection
    4. 7.4 Device Functional Modes
  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  Switching Frequency
        2. 8.2.2.2  Output Inductor Selection
        3. 8.2.2.3  Output Capacitor
        4. 8.2.2.4  Input Capacitor
        5. 8.2.2.5  Output Voltage Resistors Selection
        6. 8.2.2.6  Soft-start Capacitor Selection
        7. 8.2.2.7  Undervoltage Lockout Set Point
        8. 8.2.2.8  Bootstrap Capacitor Selection
        9. 8.2.2.9  PGOOD Pull-up Resistor
        10. 8.2.2.10 Compensation
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
    3. 10.3 Alternate Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Receiving Notification of Documentation Updates
    2. 11.2 Community Resources
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

8.2.2.1 Switching Frequency

The first step is to decide on a switching frequency for the converter. It is capable of running from 200 kHz to 1.6 MHz. Typically the highest switching frequency possible is desired because it will produce the smallest solution size. A high switching frequency allows for lower valued inductors and smaller output capacitors compared to a power supply that switches at a lower frequency. The main trade off made with selecting a higher switching frequency is extra switching power loss, which hurt the converter’s efficiency.

The maximum switching frequency for a given application is limited by the minimum on-time of the converter and is estimated with Equation 12. Using a maximum minimum on-time of 150 ns for the TPS54824 and 15 V maximum input voltage for this application, the maximum switching frequency is 800 kHz. The selected switching frequency must also consider the 10% tolerance of the switching frequency. Considering this, a switching frequency of 700 kHz was selected.Equation 13 calculates R7 to be 69.7 kΩ. A standard 1% 69.8 kΩ value was chosen in the design.

Equation 12. TPS54824 fswmax_SCO3.gif

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Equation 13. TPS54824 EQ_RTfromfsw_slvsdc9.gif