A time-interleaved analog-to-digital converter (TIADC) operates in a first mode or a second mode and includes M analog-to-digital converters (ADCs), a reference ADC, a digital correction circuit, and a control circuit. The M ADCs sample an input signal according to M enable signals to generate M digital output codes. The reference ADC samples the input signal according to a reference enable signal to generate a reference digital output code. The digital correction circuit corrects the M digital output codes to generate M corrected digital output codes. The control circuit generates the M enable signals and the reference enable signal according to a clock. The control circuit outputs the M corrected digital output codes in turn but does not output the reference digital output code in the first mode and randomly outputs the M corrected digital output codes and the reference digital output code in the second mode.