I'm a little busy with the MKR1000 
, I get not find what is the reference voltage of the analog inputs, 3.7, 1, .... ????? 
Seems little info on the Arduino site, you need to look at the chips datasheet for its full parameters.
They look very complex chips.
Check out the data sheet (its big), section 33.
http://www.atmel.com/Images/Atmel-42181-SAM-D21_Datasheet.pdf
Thank you very much for the reply 
Ok, I've seen the section 33 and the attached image, the only question I have is that it is VDDANA?
Arduino MKR1000 information is very confusing. First resolution, while in the datasheet said default gets 12-bit API in Arduino she said default is 10 bits. The reference voltage if not 3.7 or 3.3 + 0.6. Calculations with LM35 sensor does not correspond to the calculated temperature.
Someone with the same problem can help me?
Resolved, I have checked with a potentiometer and the reference voltage is 3.3V for analog pins, if someone can be helpful 