I’m building a custom circuit for fun which I intend to use to monitor a single CT and provide temperature and humidity (and optionally pulse) readings, powered from battery, using features cherry-picked from the emonTH v2 and emonTx v3. I am going to provide all of the features I need on the board, but only populate the parts I need for a particular sensor location on each board, and upload minimal firmware, to keep battery consumption low. I also want to use a switch mode power supply as used in the emonTH so I can squeeze as much juice from the batteries as possible, but I am concerned about the ripple from the part used - the LTC3525ESC6-3.3 - which is about 25-60 mV depending on load. Does this not affect the analog readings made by the emonTH? It appears there is not much filtering of this ripple, just a bunch of reasonably large capacitors but not RC or LC or LDO stabilisation.
As I understand, the ATmega328 needs a reasonably stable reference for its ADCs, so if there is 50 mV of ripple on this line then it will affect its readings.
I could use a buck-boost to regulate the voltage to ~3.5 V and pass it through an LDO to get it down to 3.3 V with low ripple if necessary, but perhaps I don’t need to…?