Various embodiments of the present invention provide circuits, systems and methods for data processing. For example, a data processing circuit is discussed that includes: an analog to digital converter circuit, a target response circuit, and a timing circuit. The analog to digital converter circuit is operable to receive a data input and to provide corresponding digital samples synchronous to a sampling phase. The sampling phase corresponds to a phase feedback. The target response circuit is operable to provide an expected output corresponding to a known input. The timing circuit is operable to generate the phase feedback based at least in part on values derived from the expected output.