SLVS632K January   2006  – January 2024 TPS5430 , TPS5431

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 (DDA Package)
    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) and Internal Compensation
      7. 6.3.7  Voltage Feed-Forward
      8. 6.3.8  Pulse-Width-Modulation (PWM) Control
      9. 6.3.9  Overcurrent Limiting
      10. 6.3.10 Overvoltage Protection
      11. 6.3.11 Thermal Shutdown
    4. 6.4 Device Functional Modes
      1. 6.4.1 Operation near Minimum Input Voltage
      2. 6.4.2 Operation with ENA control
  8. 7 Application and Implementation
    1. 7.1 Application Information
    2. 7.2 Typical Applications
      1. 7.2.1 12-V Input to 5.0-V Output
        1. 7.2.1.1 Design Requirements
        2. 7.2.1.2 Detailed Design Procedure
          1. 7.2.1.2.1 Custom Design With WEBENCH® Tools
          2. 7.2.1.2.2 Switching Frequency
          3. 7.2.1.2.3 Input Capacitors
          4. 7.2.1.2.4 Output Filter Components
            1. 7.2.1.2.4.1 Inductor Selection
            2. 7.2.1.2.4.2 Capacitor Selection
          5. 7.2.1.2.5 Output Voltage Set-Point
          6. 7.2.1.2.6 BOOT Capacitor
          7. 7.2.1.2.7 Catch Diode
          8. 7.2.1.2.8 Advanced Information
            1. 7.2.1.2.8.1 Output Voltage Limitations
            2. 7.2.1.2.8.2 Internal Compensation Network
            3. 7.2.1.2.8.3 Thermal Calculations
        3. 7.2.1.3 Application Curves
      2. 7.2.2 Wide Input Voltage Ranges with TPS5430
        1. 7.2.2.1 Design Requirements
        2. 7.2.2.2 Detailed Design Procedure
        3. 7.2.2.3 Wide Input Voltage Ranges with TPS5431
          1. 7.2.2.3.1 Design Requirements
          2. 7.2.2.3.2 Detailed Design Procedure
      3. 7.2.3 Circuit Using Ceramic Output Filter Capacitors
        1. 7.2.3.1 Design Requirements
        2. 7.2.3.2 Detailed Design Procedure
          1. 7.2.3.2.1 Output Filter Component Selection
          2. 7.2.3.2.2 External Compensation Network
    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 Device Support
      1. 8.1.1 Third-Party Products Disclaimer
      2. 8.1.2 Development Support
        1. 8.1.2.1 Custom Design With WEBENCH® Tools
    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
7.2.3.2.2 External Compensation Network

When using ceramic output capacitors, additional circuitry is required to stabilize the closed loop system. For this circuit, the external components are R3, C4, C6, and C7. To determine the value of these components, first calculate the LC resonant frequency of the output filter:

Equation 17. GUID-7D4DF580-465D-486B-AC33-FA219D0654C6-low.gif

For this example the effective resonant frequency is calculated as 4109 Hz

The network composed of R1, R2, R3, C5, C6, and C7 has two poles and two zeros that are used to tailor the overall response of the feedback network to accommodate the use of the ceramic output capacitors. The pole and zero locations are given by the following equations:

Equation 18. GUID-FE92D255-F880-4FFC-A79D-C919177D5819-low.gif
Equation 19. GUID-829A1AC2-181E-4B22-80FF-5317D9FD42AE-low.gif
Equation 20. GUID-16258D2B-380A-4EA8-9BE3-23FDD0367E80-low.gif

The final pole is located at a frequency too high to be of concern. The second zero, fz2 as defined by Equation 20 uses 2.5 for the frequency multiplier. In some cases this can need to be slightly higher or lower. Values in the range of 2.3 to 2.7 work well. The values for R1 and R2 are fixed by the 3.3 V output voltage as calculated using Equation 12. For this design R1 = 10 kΩ and R2 = 5.90 kΩ. With Fp1 = 401 Hz, Fz1 = 2876 Hz and Fz2 = 10.3 kHz, the values of R3, C6 and C7 are determined using Equation 21, Equation 22, and Equation 23:

Equation 21. GUID-1F44E204-49FB-406D-A88B-986B88DE4444-low.gif
Equation 22. GUID-1E2C0BA8-AB32-4604-A6ED-0E4B7357E7E6-low.gif
Equation 23. GUID-F8FB70E7-64B1-4AAB-8F28-2342C80A236A-low.gif

For this design, using the closest standard values, C7 is 0.1 μF, R3 is 549 Ω, and C6 is 1500 pF. C4 is added to improve load regulation performance. It is effectively in parallel with C6 in the location of the second pole frequency, so it must be small in relationship to C6. C4 must be less the 1/10 the value of C6. For this example, 150 pF works well.

For additional information on external compensation of the TPS5430, TPS5431 or other wide voltage range devices, see the Using TPS5410/20/30/31 With Aluminum/Ceramic Output Capacitors application report.