A 2.2-ps Two-Dimensional Gated-Vernier Time-to-Digital Converter With Digital Calibration
This brief presents a two-dimensional (2-D) Vernier time-to-digital converter (TDC) which uses two 3-stage gated ring oscillators (GROs) in the X/Y Vernier branches. The already small Vernier quantization noise (~10.6 ps) is improved by the first-order noise shaping of the GRO. Moreover, since all the delay differences between the X and Y phases can be used (rather than only the diagonal line of the one-dimensional architecture), the intrinsic large latency time of the Vernier architecture is dramatically reduced. The TDC is implemented in a 65-nm CMOS process and consumes 2.3 mA from 1.0 V. The measured total noise integrated over a bandwidth of 1.25 MHz yields an equivalent TDC resolution of 2.2 ps, whereas the average latency time (within 2 ns) is less than 1/6 of that in a standard Vernier TDC.