SLVS861F august   2008  – june 2020 TPS40210-Q1 , TPS40211-Q1

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     4
  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 Timing Requirements
    7. 6.7 Switching Characteristics
    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  Minimum On-Time and Off-Time Considerations
      2. 7.3.2  Current Sense and Overcurrent
      3. 7.3.3  Current Sense and Subharmonic Instability
      4. 7.3.4  Current Sense Filtering
      5. 7.3.5  Soft Start
      6. 7.3.6  BP Regulator
      7. 7.3.7  Shutdown (DIS/ EN Pin)
      8. 7.3.8  Control Loop Considerations
      9. 7.3.9  Gate Drive Circuit
      10. 7.3.10 TPS40211-Q1
    4. 7.4 Device Functional Modes
      1. 7.4.1 Setting the Oscillator Frequency
      2. 7.4.2 Synchronizing the Oscillator
  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  Duty Cycle Estimation
        2. 8.2.2.2  Inductor Selection
        3. 8.2.2.3  Rectifier Diode Selection
        4. 8.2.2.4  Output Capacitor Selection
        5. 8.2.2.5  Input Capacitor Selection
        6. 8.2.2.6  Current Sense and Current Limit
        7. 8.2.2.7  Current Sense Filter
        8. 8.2.2.8  Switching MOSFET Selection
        9. 8.2.2.9  Feedback Divider Resistors
        10. 8.2.2.10 Error Amplifier Compensation
        11. 8.2.2.11 R-C Oscillator
        12. 8.2.2.12 Soft-Start Capacitor
        13. 8.2.2.13 Regulator Bypass
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Related Links
    4. 11.4 Receiving Notification of Documentation Updates
    5. 11.5 Support Resources
    6. 11.6 Trademarks
    7. 11.7 Electrostatic Discharge Caution
    8. 11.8 Glossary
  12. 12Mechanical, Packaging, and Orderable Information
    1.     69

8.2.2.2 Inductor Selection

The peak-to-peak ripple is limited to 30% of the maximum output current.

Equation 34. GUID-6D239EDC-C38C-4EFB-8A54-529E5BCCF385-low.gif

The minimum inductor size can be estimated using Equation 35.

Equation 35. GUID-7E365795-A126-472D-8961-68022F98E0A1-low.gif

The next higher standard inductor value of 10 μH is selected. The ripple current is estimated by Equation 36.

Equation 36. GUID-A0088E37-E201-43BA-A50A-6E35602CAD8A-low.gif
Equation 37. GUID-0199ECF6-335F-4DF9-A766-85AC96E58915-low.gif

The worst-case peak-to-peak ripple current occurs at 50% duty cycle and is estimated as 1.02 A. Worst-case rms current through the inductor is approximated by Equation 38.

Equation 38. GUID-B317A5B7-6449-4085-83D8-58FDBF3F8997-low.gif

The worst case RMS inductor current is 6.13 Arms. The peak inductor current is estimated by Equation 39.

Equation 39. GUID-780707DE-C557-4A14-BD74-2F2A0187E31F-low.gif

A 10-μH inductor with a minimum RMS current rating of 6.13 A and minimum saturation current rating of 6.57 A must be selected. A TDK RLF12560T-100M-7R5 7.5-A 10-μH inductor is selected.

This inductor power dissipation is estimated by Equation 40.

Equation 40. GUID-281AAF1D-7B2F-4415-9274-9FABBC335A0A-low.gif

The TDK RLF12560T-100M-7R5 12.4-mΩ DCR dissipates 466 mW of power.