Abstract: A data separator for use in synchronizing data derived from a floppy disk or similar data source provides a variable net gain or loss of charge to vary the frequency of a voltage-controlled oscillator in accordance with the relative position of the data with respect to the clock until data centering or synchronization is achieved. The net charge is derived from a charge pump circuit that is controlled by a charge pump-up signal whose duration is proportional to the detected phase difference between the data and the clock, and a charge pump-down signal whose duration is one clock cycle. When the data pulse is centered within a clock cycle, the duration of a pump-up signal is one half that of a pump-down signal.