PSoC SAR ADC resolution will be Vref/2^n, wherere n is the no, of resolution bits. Even though the Vref value can be any value greater than zero on component configuration, all the specifications guaranteed in the datasheet are up to a minimum voltage of 1.024 V. So this is will set the sensitivity of the ADC around 1mV. With averaging to some extend you can attain somewhat higher resolution. Above all this you have to make sure that you have to make sure to the complete range of the ADC(in single ended mode if Vneg is connected to VSSA, it is not possible- resolution reduced to 11 bits.)
thank you for your response. In other hand, do you know if there´s a maximun value to convert?
The maximum value you can convert is dependent upon the ADC input range of operation. This will depend on the Vref you have chosen and where the negative input of the ADC is connected. Check the component datasheet for following table.
Over all this the hard limit on the input is the device maximum and minimum voltgae, which VDDA and VSS. Any voltage outside this may not be directly measured.