How to find the dynamic range of ADC?
The dynamic range is the ratio of the maximum voltage to the minimum voltage that the ADC can convert.  The maximum voltage is 5 volts.  Since it is a 12 bit converter, it has a resolution of 212 - 1 or 4095.  Thus the minimum voltage, for which the ADC would have only the least significant bit set, is 1.22 millivolts.  So the dynamic range of your ADC is 5/.00122 = 4095 = 72.2 dB. In general, the dynamic range is only a function of the number of bits, not the maximum input voltage. But I calculated using voltage just to show you the details.