The present invention provides for background calibration of a time-interleaved analog-to-digital converter (TIADC). In one embodiment, a background calibrator includes a TIADC having a parallel array of time-interleaved main signal processors, each main signal processor including an ADC connected to a corresponding output FIR filter. The background calibrator also includes an auxiliary signal processor having an ADC connected to at least one corresponding output FIR filter. Additionally, the background calibrator further includes a timing calibration circuit, wherein the timing calibration circuit is configured to select one of the main signal processors, exchange the auxiliary signal processor with the selected main signal processor in the TIADC and connect the selected main signal processor to the timing calibration circuit. In an alternative embodiment, the timing calibration circuit is further configured to reduce a timing mismatch of the selected main signal processor.