A TDC circuit configured to receive a reference clock (REF) signal and a signal derived from a LO; generate a plurality of digital values indicative of a measured phase difference between the signal derived from the LO and the REF signal, wherein each of the plurality of digital values are determined from a unique set of a plurality of sets of TDC measurement component quantization levels; generate a combined series of quantization levels based on a combination of the plurality of sets of TDC measurement component quantization levels; and determine a combined digital value from the combined series of quantization levels and at least one of the plurality of digital values to generate an output of the TDC circuit. The combined series of quantization levels may be generated by summing simultaneously occurring levels of each of the plurality of sets of TDC measurement component quantization levels together.