A bipolar TDC apparatus with a phase detection and signal switching circuitry and a phase error measurement circuitry. The phase detection and signal switching circuitry include a multiplexer and phase detector, together referred to as PD_MUX. The PD_MUX is used to handle the order of the two input signal phases of a TDC, or in other words, to enable TDC the bipolarity detection of the phase error. The apparatus detects first the polarity of the phase error and then prepares the right phase order when they arrive at the TDC measurement elements of the phase error measurement circuitry to ensure that always the earlier one starts the TDC and the later one triggers the measurement event. As such, the phase measurement circuitry (or measurement block) provides the phase error magnitude information, while the PD_MUX provides the sign—polarity information.