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DC/DC conversion for MCU core supply

Today’s automotive systems for powertrain application (electronic fuel injection), safety applications (electric power steering, radar system, braking ECU) and body applications are increasingly complex. To meet the processing demands designers are moving to ever more powerful multi-core processors running at 1.8 V or 0.9 V with a switching frequency of 0.4 – 1.8 MHz. While this brings numerous advantages, it also adds strain to ensuring a stable core supply voltage while minimizing on-chip thermals. One approach to solve this is to incorporate a simple discrete P-/N-channel MOSFET buck converter.

Block diagram

Design considerations

  • Including a buck converter inside the µC would produce too much heat and occupy to much crystal area
  • Control logic for the buck converter can be integrated into the µC, with drivers and related PWM control via a feedback loop.
  • BoM cost for µC core supply is reduced, as you only need the 2 external MOSFETs + inductor.
  • Using P-channel as high-side switch eliminates the need for a bootstrap circuit and reduces the drive voltage from the MCU.
  • Design is already used by several automotive controllers