thank you andre, but this is not the problem the problem is that i have 40Ah battery used in a car and i would like to supply the microcontroller from the battery, the voltage of the battery is between 1.8 and 3.2V, without using a dc-dc how can i do this ?
You can use linear regulator, due few amount of current required.
However, you must take a lot of care concerning spike protection ( filtering ), due amount of noise propagated by sparking performed at motor.