SLVSDG6C May   2016  – March 2026 TPS54302

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 Timing Requirements
    7. 5.7 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  Fixed-Frequency PWM Control
      2. 6.3.2  Pulse Skip Mode
      3. 6.3.3  Error Amplifier
      4. 6.3.4  Slope Compensation and Output Current
      5. 6.3.5  Enable and Adjusting Undervoltage Lockout
      6. 6.3.6  Safe Start-Up into Prebiased Outputs
      7. 6.3.7  Voltage Reference
      8. 6.3.8  Adjusting Output Voltage
      9. 6.3.9  Internal Soft Start
      10. 6.3.10 Bootstrap Voltage (BOOT)
      11. 6.3.11 Overcurrent Protection
        1. 6.3.11.1 High-Side MOSFET Overcurrent Protection
        2. 6.3.11.2 Low-Side MOSFET Overcurrent Protection
      12. 6.3.12 Spread Spectrum
      13. 6.3.13 Output Overvoltage Protection (OVP)
      14. 6.3.14 Thermal Shutdown
    4. 6.4 Device Functional Modes
      1. 6.4.1 Normal Operation
      2. 6.4.2 Eco-mode Operation
  8. 7 Application and Implementation
    1. 7.1 Application Information
    2. 7.2 Typical Application
      1. 7.2.1 TPS54302 8V to 28V Input, 5V Output Converter
      2. 7.2.2 Design Requirements
      3. 7.2.3 Detailed Design Procedure
        1. 7.2.3.1 Input Capacitor Selection
        2. 7.2.3.2 Bootstrap Capacitor Selection
        3. 7.2.3.3 Output Voltage Set Point
        4. 7.2.3.4 Undervoltage Lockout Set Point
        5. 7.2.3.5 Output Filter Components
          1. 7.2.3.5.1 Inductor Selection
          2. 7.2.3.5.2 Output Capacitor Selection
          3. 7.2.3.5.3 Feedforward Capacitor
      4. 7.2.4 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 Device Support
      1. 8.1.1 Third-Party Products Disclaimer
    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

7.2.3.1 Input Capacitor Selection

The device requires an input decoupling capacitor and a bulk capacitor is needed depending on the application. TI recommends a ceramic capacitor over 10µF for the decoupling capacitor. An additional 0.1µF capacitor (C2) from the VIN pin to GND is optional to provide additional high frequency filtering. The capacitor voltage rating must be greater than the maximum input voltage.

Use Equation 4 to calculate the input ripple voltage (ΔVIN).

Equation 4. TPS54302

where

  • CBULK is the bulk capacitor value.
  • fSW is the switching frequency.
  • IOUT(MAX) is the maximum loading current.
  • ESRMAX is maximum series resistance of the bulk capacitor.

The maximum RMS (root mean square) ripple current must also be checked. For worst case conditions, use Equation 5 to calculate ICIN(RMS).

Equation 5. TPS54302

The actual input-voltage ripple is greatly affected by parasitic associated with the layout and the output impedance of the voltage source. The Design Requirements show the actual input voltage ripple for this circuit which is larger than the calculated value. This measured value is still below the specified input limit of 400mV. The maximum voltage across the input capacitors is VINmax + ΔVIN / 2. The selected bypass capacitor is rated for 35V and the ripple current capacity is greater than 2A. Both values provide ample margin. The maximum ratings for voltage and current must not be exceeded under any circumstance.