Review of pulse generators for gated ring oscillator based Time-to-Digital converters

Pulse generator serves an important role in gated ring oscillator (GRO) based Time-to-Digital converters (TDC) to enable the ring oscillator for the input time difference between two reference timing events. As the resolution of TDC advances to a few picoseconds, the linearity of the pulse generator becomes increasingly important. This paper reviews and compare between pulse generators implemented using a XOR gate, SR latch, phase frequency detector (PFD) and time difference generator (TDG). Simulation results in standard 40nm CMOS technology shows that the TDG is the most suitable pulse generator since it has the best linearity. In terms of power and area, the dynamic PFD is a good alternative.