I was thinking of powering a microcontroller directly from a buck-boost converter, but after doing a few calculations I ran into the following problems: Ringing when switching on/off Current rise time You can get the ringing down with a snubber. The current rise time however is a big problem. Imagine that the micro is in sleep mode and it is woken up. All of a sudden a higher current is required. The control system disconnects the load from the power supply and starts charging the inductor. The inductor needs to be charged to the higher current before the capacitor drops below the permissible microcontroller voltage (say 5%). I ran some calculations for a current of 100mA and I ended up with huge capacitor values (mF for a rise time of a ms). So I was wondering is it at all possible to power a microcontroller directly from an SMPS? Obviously you can increase the current slew rate but then your switching frequency goes through the roof.