SLUS964D NOVEMBER   2009  – March 2018 TPS40303 , TPS40304 , TPS40305

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Simplified Application Diagram
  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 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 Voltage Reference
      2. 7.3.2 Enable Functionality, Start-Up Sequence and Timing
      3. 7.3.3 Soft-Start Time
      4. 7.3.4 Oscillator and Frequency Spread Spectrum (FSS)
      5. 7.3.5 Overcurrent Protection
      6. 7.3.6 Drivers
      7. 7.3.7 Prebias Start-Up
      8. 7.3.8 Power Good
      9. 7.3.9 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 Modes of Operation
        1. 7.4.1.1 UVLO
        2. 7.4.1.2 Disable
        3. 7.4.1.3 Calibration
        4. 7.4.1.4 Converting
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 Using the TPS40305 for a 12-V to 1.8-V Point-of-Load Synchronous Buck Regulator
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1  Custom Design With WEBENCH® Tools
          2. 8.2.1.2.2  Selecting the Switching Frequency
          3. 8.2.1.2.3  Inductor Selection (L1)
          4. 8.2.1.2.4  Output Capacitor Selection (C12)
          5. 8.2.1.2.5  Peak Current Rating of Inductor
          6. 8.2.1.2.6  Input Capacitor Selection (C8)
          7. 8.2.1.2.7  MOSFET Switch Selection (Q1 and Q2)
          8. 8.2.1.2.8  Bootstrap Capacitor (C6)
          9. 8.2.1.2.9  VDD Bypass Capacitor (C7)
          10. 8.2.1.2.10 BP Bypass Capacitor (C5)
          11. 8.2.1.2.11 Short-Circuit Protection (R11)
          12. 8.2.1.2.12 Feedback Divider (R4, R5)
          13. 8.2.1.2.13 Compensation: (C2, C3, C4, R3, R6)
        3. 8.2.1.3 Application Curves
      2. 8.2.2 A High-Current, Low-Voltage Design Using the TPS40304
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
          1. 8.2.2.2.1  Selecting the Switching Frequency
          2. 8.2.2.2.2  Inductor Selection (L1)
          3. 8.2.2.2.3  Output Capacitor Selection (C12)
          4. 8.2.2.2.4  Peak Current Rating of Inductor
          5. 8.2.2.2.5  Input Capacitor Selection (C8)
          6. 8.2.2.2.6  MOSFET Switch Selection (Q1 and Q2)
          7. 8.2.2.2.7  Bootstrap Capacitor (C6)
          8. 8.2.2.2.8  VDD Bypass Capacitor (C7)
          9. 8.2.2.2.9  BP Bypass Capacitor (C5)
          10. 8.2.2.2.10 Short-Circuit Protection (R11)
          11. 8.2.2.2.11 Feedback Divider (R4, R5)
          12. 8.2.2.2.12 Compensation: (C2, C3, C4, R3, R6)
        3. 8.2.2.3 Application Curves
      3. 8.2.3 A Synchronous Buck Application Using the TPS40303
        1. 8.2.3.1 Design Requirements
        2. 8.2.3.2 Detailed Design Procedure
          1. 8.2.3.2.1  Selecting the Switching Frequency
          2. 8.2.3.2.2  Inductor Selection (L1)
          3. 8.2.3.2.3  Output Capacitor Selection (C12)
          4. 8.2.3.2.4  Peak Current Rating of Inductor
          5. 8.2.3.2.5  Input Capacitor Selection (C8)
          6. 8.2.3.2.6  MOSFET Switch Selection (Q1 and Q2)
          7. 8.2.3.2.7  Bootstrap Capacitor (C6)
          8. 8.2.3.2.8  VDD Bypass Capacitor (C7)
          9. 8.2.3.2.9  BP Bypass Capacitor (C5)
          10. 8.2.3.2.10 Short-Circuit Protection (R11)
          11. 8.2.3.2.11 Feedback Divider (R4, R5)
          12. 8.2.3.2.12 Compensation: (C2, C3, C4, R3, R6)
        3. 8.2.3.3 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 Custom Design With WEBENCH® Tools
    3. 11.3 Documentation Support
      1. 11.3.1 Related Documentation
    4. 11.4 Related Links
    5. 11.5 Receiving Notification of Documentation Updates
    6. 11.6 Community Resources
    7. 11.7 Trademarks
    8. 11.8 Electrostatic Discharge Caution
    9. 11.9 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

8.2.2.2.2 Inductor Selection (L1)

Synchronous buck power inductors are typically sized for approximately 30% peak-to-peak ripple current (IRIPPLE)

Given this target ripple current, the required inductor size can be calculated in Equation 19.

Equation 19. TPS40303 TPS40304 TPS40305 4equation1.gif

Selecting a standard 300-nH inductor value, solve for IRIPPLE = 6 A

The RMS current through the inductor is approximated by Equation 20.

Equation 20. TPS40303 TPS40304 TPS40305 4equation2.gif