TIDUFH5 March   2026 TPSI31P1-Q1

 

  1.   1
  2.   Description
  3.   Resources
  4.   Features
  5.   Applications
  6.   6
  7. 1System Description
  8. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
      1. 2.2.1  Control Logic
      2. 2.2.2  Switching Power
        1. 2.2.2.1 Calculation: D
        2. 2.2.2.2 Calculation: 1 – D
        3. 2.2.2.3 Calculation: D + (1 – D)
      3. 2.2.3  Propagation Delay
      4. 2.2.4  MOSFET Selection
      5. 2.2.5  Flyback or Freewheeling Diode Selection
      6. 2.2.6  Sense Resistance Selection
      7. 2.2.7  Input Capacitance Selection
      8. 2.2.8  Output Capacitance Selection
      9. 2.2.9  Design Example #1: Single RSENSE Configuration
      10. 2.2.10 Design Example #2: Double RSENSE Configuration
    3. 2.3 Highlighted Products
      1. 2.3.1 TPSI31P1-Q1
      2. 2.3.2 TPS7A49
  9. 3Hardware, Software, Testing Requirements, and Test Results
    1. 3.1 Hardware Requirements
    2. 3.2 Test Setup
    3. 3.3 Test Results
  10. 4Design and Documentation Support
    1. 4.1 Design Files
      1. 4.1.1 Schematics
      2. 4.1.2 BOM
      3. 4.1.3 PCB Layout Recommendations
        1. 4.1.3.1 Use Large Return Planes to Contain Electromagnetic Fields
        2. 4.1.3.2 Minimize High diL/dt Loop Length to Control Oscillations and EMI
        3. 4.1.3.3 Minimize SW Node Area to Improve Ringing and Noise
        4. 4.1.3.4 Minimize Inductor Pad to Limit Parasitic Capacitive Coupling
        5. 4.1.3.5 HV Creepage and Clearance
        6. 4.1.3.6 Layout Prints
    2. 4.2 Tools
    3. 4.3 Documentation Support
    4. 4.4 Support Resources
    5. 4.5 Trademarks
  11. 5About the Authors

2.2.7 Input Capacitance Selection

Figure 2-8 shows how the input capacitance stabilizes the voltage and provides charge during the TON period. The required capacitance can be calculated based on the allowed voltage ripple ΔVIN.

TIDA-050082 Charge Required During TON Figure 2-8 Charge Required During TON

where

Q I N = I A V G × T O N; Q I N = C I N × ∆ V I N; ∆ V I N = I A V G C I N × T O N

Depending on system parasitic elements, the input capacitance likely does not need to provide all the input charge since the battery also helps provide input charge.