Analog to digital converter device and method for calibrating clock skew

An analog to digital converter (ADC) device includes ADC circuits, a calibration circuit, and a skew adjusting circuit. The ADC circuits convert an input signal according to interleaved clock signals, in order to generate first quantized outputs. The calibration circuit performs at least one calibration computation according to the first quantized outputs to generate second quantized outputs. The skew adjusting circuit determines calculating signals, to which the second quantized outputs correspond in a predetermined interval, and averages the calculating signals to generate a reference signal, and compares the reference signal with each of the calculating signals to generate detecting signals, and determines whether the detecting signals are adjusted or not according to a signal frequency to generate adjusting signals, in order to reduce a clock skew in the ADC circuits.