According to a method of Successive Approximation Register (SAR) analog to digital conversion, N+1 SAR cycles are performed to obtain an output digital code having N bits. An analog signal is sampled and obtained. After execution of the first N−1 SAR cycles, the Nth SAR cycle is performed by setting a Nth tentative analog signal corresponding to a provisional digital code and comparing the Nth tentative analog signal with the sampled analog signal to obtain a Nth comparison result. The (N+1)th SAR cycle is performed by setting a (N+1)th tentative analog signal based on the Nth comparison result, comparing the (N+1)th tentative analog signal with the sampled analog signal to obtain a second comparison result, and correcting the provisional digital code based on the (N+1)th comparison result to obtain the output digital code. The Nth and (N+1)th SAR cycles each comprise a plurality sub-comparisons and yield a set of sub-results.