A multistage analog/digital converter for converting in multi-step cycles an input signal into respective digital codes, each cycle step resolving at least one bit of a respective digital code. The converter includes: a sampling circuit inputting the signal and outputting a first sequence of analog samples; a generation block of a pseudorandom sequence of samples; a summing node, such as to input the first sequence and the pseudorandom sequence, obtaining in output a second sequence of analog samples including non-pseudorandom samples; a converter having a controllable digital gain receiving the second sequence and outputting bits of the digital codes; a feedback loop with a loop gain and including an analog amplifier; a digital calibration block to match the digital gain to the loop gain and including a prediction block to produce a digital estimation of said input signal starting from the bits resulting from converting the non-pseudorandom samples.