SLVS675E August   2006  – January 2024 TPS5410

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information 
    5. 5.5 Electrical Characteristics
    6. 5.6 Typical Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1  Oscillator Frequency
      2. 6.3.2  Voltage Reference
      3. 6.3.3  Enable (ENA) and Internal Slow-Start
      4. 6.3.4  Undervoltage Lockout (UVLO)
      5. 6.3.5  Boost Capacitor (BOOT)
      6. 6.3.6  Output Feedback (VSENSE)
      7. 6.3.7  Internal Compensation
      8. 6.3.8  Voltage Feed-Forward
      9. 6.3.9  Pulse-Width-Modulation (PWM) Control
      10. 6.3.10 Overcurrent Limiting
      11. 6.3.11 Overvoltage Protection
      12. 6.3.12 Thermal Shutdown
    4. 6.4 Device Functional Modes
      1. 6.4.1 Minimum Input Voltage
      2. 6.4.2 ENA Control
  8. 7 Applications and Implementation
    1. 7.1 Application Information
    2. 7.2 Typical Applications
      1. 7.2.1 Application Circuit
        1. 7.2.1.1 Design Requirements
        2. 7.2.1.2 Detailed Design Procedure
          1. 7.2.1.2.1 Switching Frequency
          2. 7.2.1.2.2 Input Capacitors
          3. 7.2.1.2.3 Output Filter Components
            1. 7.2.1.2.3.1 Inductor Selection
            2. 7.2.1.2.3.2 Capacitor Selection
          4. 7.2.1.2.4 Output Voltage Setpoint
          5. 7.2.1.2.5 Boot Capacitor
          6. 7.2.1.2.6 Catch Diode
          7. 7.2.1.2.7 Advanced Information
            1. 7.2.1.2.7.1 Output Voltage Limitations
            2. 7.2.1.2.7.2 Internal Compensation Network
            3. 7.2.1.2.7.3 Thermal Calculations
        3. 7.2.1.3 Application Curves
      2. 7.2.2 Using All Ceramic Capacitors
        1. 7.2.2.1 Design Requirements
        2. 7.2.2.2 Detailed Design Procedure
          1. 7.2.2.2.1 Output Filter Capacitor Selection
          2. 7.2.2.2.2 External Compensation Network
        3. 7.2.2.3 Application Curves
    3. 7.3 Power Supply Recommendations
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
      2. 7.4.2 Layout Example
  9. 8 Device and Documentation Support
    1. 8.1 Documentation Support
      1. 8.1.1 Related Documentation
    2. 8.2 Receiving Notification of Documentation Updates
    3. 8.3 Support Resources
    4. 8.4 Trademarks
    5. 8.5 Electrostatic Discharge Caution
    6. 8.6 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information
7.2.1.2.3.1 Inductor Selection

To calculate the minimum value of the output inductor, use Equation 4:

Equation 4. GUID-84D38526-3838-488A-AEF0-120DB9EFBE03-low.gif

KIND is a coefficient that represents the amount of inductor ripple current relative to the maximum output current. Three things must be considered when determining the amount of ripple current in the inductor: the peak to peak ripple current affects the output ripple voltage amplitude, the ripple current affects the peak switch current, and the amount of ripple current determines at what point the circuit becomes discontinuous. For designs using the TPS5410, KIND of 0.2 to 0.3 yields good results. Low output ripple voltages is obtained when paired with the proper output capacitor, the peak switch current is below the current limit set point, and low load currents can be sourced before discontinuous operation.

For this design example, use KIND = 0.3, and the minimum inductor value is 66 μH. The next highest standard value used in this design is 68 μH.

For the output filter inductor, the RMS current and saturation current ratings not being exceeded is important. The RMS inductor current can be found from Equation 5:

Equation 5. GUID-D8B9C3CB-AE2B-474A-8603-E976B640A1F0-low.gif

and the peak inductor current can be determined using Equation 6:

Equation 6. GUID-13AB7659-BBD3-4E09-BDA0-86AC209B3B05-low.gif

For this design, the RMS inductor current is 1.004 A, and the peak inductor current is 1.147 A. The chosen inductor is a Coilcraft MSS1260-683 type. The nominal inductance is 68μH. It has a saturation current rating of 2.3 A and a RMS current rating of 2.3 A, which meets the requirements. Inductor values for use with the TPS5410 are in the range of 10 μH to 100 μH.