Abstract: A phase to digital converter (PDC) generates a digital output that represents a phase difference between first and second clocks. The PDC includes a gated ring oscillator (GRO), which includes N signal delay elements coupled together in a ring via a logic gate, wherein a 1st signal delay element of the ring comprises an input coupled to an output of the logic gate, and wherein a Nth signal delay element of the ring comprises an output coupled to a first input of the logic gate. A convertor is coupled to the GRO and configured to generate low order bits of the digital output based on outputs of the logic gate and the N signal delay elements. A first counter includes an input coupled to an output of one of the N signal delay elements or the logic gate, wherein the first counter is configured to generate a first digital counter value.