An internal coil interface implantable within the body of a patient and configured to modulate a load on an internal coil, and a method therefore are provided. According to one aspect, processing circuitry of the internal coil interface is configured to predict a time of a first voltage level crossing by a voltage at a terminal of the internal coil for each of a plurality of successive windows each time the capacitance is switched into the modulated load circuit or each time the capacitance is switched out of the modulated load circuit. The process is also configured to adjust the predictions based on whether a previous prediction of a time of a first voltage level crossing for a window was later or earlier than a time at which the first voltage level crossing actually occurred.