This work presents a fully digital background calibration technique of timing mismatch in time-interleaved analog-to-digital converters (TIADCs). The timing mismatch is estimated by the correlation function of adjacent channels’ digital outputs. The proposed estimation method is suitable for an arbitrary number of channels. Compared with the traditional fixed step-size least mean square (LMS) algorithm, a variable step-size iteration algorithm is adopted to ensure accurate estimation parameters and fast convergence speed. A coarse-fine correction structure based on two-order Taylor series is proposed to satisfy the high-precision correction. Simulation results show that the proposed calibration technique increases the signal-to-noise-and-distortion (SNDR) and spurious-free dynamic range (SFDR) from 30.18 and 30.69 dB to 79.69 and 93.94 dB, respectively.