Alexandre Guimaraes wrote:

>> If you're using a zener regulator, the cap is mainly for filtering
>> (doesn't have to be big for that) and for surviving short gaps in power
>> supply (not sure how important that is).
> 
> This is what I am still evaluating... I need to survive power supply
> "outages" when the starting engine is being turned and the battery is
> almost dead. 

I don't know how frequent it is that a battery goes below 5V during
starting. I'm not sure, but I gather that there isn't much starting torque
anymore at this voltage, so maybe you can design with a workable minimum
voltage.

Gerhard

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