SLVSAA4G June   2010  – February 2018 TPS65251

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Typical Application Schematic
  4. 4 Revision History
  5. 5 Description (continued)
  6. 6 Pin Configuration and Functions
    1.     Pin Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1  Adjustable Switching Frequency
      2. 8.3.2  Synchronization
      3. 8.3.3  Out-of-Phase Operation
      4. 8.3.4  Delayed Start-Up
      5. 8.3.5  Soft-Start Time
      6. 8.3.6  Adjusting the Output Voltage
      7. 8.3.7  Input Capacitor
      8. 8.3.8  Bootstrap Capacitor
      9. 8.3.9  Error Amplifier
      10. 8.3.10 Loop Compensation
      11. 8.3.11 Slope Compensation
      12. 8.3.12 Powergood
      13. 8.3.13 Current Limit Protection
      14. 8.3.14 Overvoltage Transient Protection
      15. 8.3.15 Thermal Shutdown
    4. 8.4 Device Functional Modes
      1. 8.4.1 Low-Power Mode Operation
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1  Loop Compensation Circuit
        2. 9.2.2.2  Selecting the Switching Frequency
        3. 9.2.2.3  Output Inductor Selection
        4. 9.2.2.4  Output Capacitor
        5. 9.2.2.5  Input Capacitor
        6. 9.2.2.6  Soft-Start Capacitor
        7. 9.2.2.7  Bootstrap Capacitor Selection
        8. 9.2.2.8  Adjustable Current Limiting Resistor Selection
        9. 9.2.2.9  Output Voltage and Feedback Resistors Selection
        10. 9.2.2.10 Compensation
        11. 9.2.2.11 3.3-V and 6.5-V LDO Regulators
      3. 9.2.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
    3. 11.3 Power Dissipation
  12. 12Device and Documentation Support
    1. 12.1 Receiving Notification of Documentation Updates
    2. 12.2 Community Resources
    3. 12.3 Trademarks
    4. 12.4 Electrostatic Discharge Caution
    5. 12.5 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

9.2.2.3 Output Inductor Selection

To calculate the value of the output inductor, use Equation 16. KIND is a coefficient that represents the amount of inductor ripple current relative to the maximum output current. In general, KIND is normally from 0.1 to 0.3 for the majority of applications.

For this design example, use KIND = 0.2 and the inductor value is calculated to be 3.6 µH. For this design, a nearest standard value was chosen: 4.7 µH. For the output filter inductor, it is important that the RMS current and saturation current ratings not be exceeded. The RMS and peak inductor current can be found from Equation 17 and Equation 18.

Equation 16. TPS65251 eq10_lvsaa3.gif
Equation 17. TPS65251 eq11_lvsaa3.gif
Equation 18. TPS65251 eq12_lvsaa3.gif
Equation 19. TPS65251 eq13_lvsaa3.gif