SNVAA98 January   2024 LM25148 , LM74910-Q1 , TPS38700 , TPS389006 , TPS389006-Q1 , TPS628301 , TPS628302 , TPS628303 , TPS6287B10 , TPS6287B25 , TPS746

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1 Introduction
  5. 2 Design Parameters
  6. 3 Schematics
  7. 4 Design Considerations
  8. 5 Front-End Protection
  9. 6 3.3V Always-ON Bias Supply
  10. 7 5V Pre-Regulator Buck Converter
  11. 8 Low-Voltage High-Current Core Rail Buck Converter
  12. 9 On-Board Core Rail Output Load Transient Stepper
  13. 10Multiple Peripheral Rail Buck Converters Sub-Circuits Schematic
  14. 11Voltage Supervisor and Sequencer
  15. 1212-Channel Sequencer Alternative
  16. 13Summary
  17. 14References

7 5V Pre-Regulator Buck Converter

All of the Point-of-Load (POL) converters in this system regulate relatively low voltages. To have a solution that optimizes for size, cost, and complexity, it is more viable to use POL converters that are optimized for low-voltage applications, which can usually accept maximum input voltages of around 5V. This brings in the need to have a pre-regulator converter that accepts a wide input voltage and regulates the intermediary voltage of 5V. The LM25148, a wide-input synchronous buck controller IC, is used for this purpose. The LM25148 is set to run at a switching frequency of 440kHz. The LM25148 includes features such as dithering or spread-spectrum for improved EMI performance, integrated bootstrap diode for the high-side driver supply, the capability of programming the output voltage without the use of feedback resistor dividers, and other features that can be found in the device data sheet.