SLUU180B January   2022  – February 2022 TPS40070 , TPS40071

 

  1.   Trademarks
  2. 1Introduction
  3. 2Description
  4. 3Schematic
    1. 3.1 Output Filter Components
    2. 3.2 MOSFET Selection
    3. 3.3 Frequency Feedforward Resistor Selection
    4. 3.4 Output Voltage Setpoint
    5. 3.5 Short Circuit Protection Resistor Selection
    6. 3.6 Miscellaneous Parts
    7. 3.7 Control Loop Compensation
  5. 4Test Setup
  6. 5Results
    1. 5.1 Control Loop Characteristics
  7. 6Assembly Drawing and PCB Layout
  8. 7List of Materials
  9. 8Reference
  10. 9Revision History

3.2 MOSFET Selection

The power MOSFET selection is made with the knowledge that it is difficult to choose one set of components that are optimal over the entire operation range. From maximum VIN to minimum VIN, the switch duty cycle can vary from approximately 10% to over 66%. The Vishay Si7860DP is found to be a robust choice for both upper and lower positions with 8-mW RDS(on) and less than 30-nC gate charge to keep switching losses low. D1 is included to add to provide maximum boost voltage when VIN is a the low end of its range.