A 1-1 MASH 2-D vernier time-to-digital converter with 2nd-order noise shaping

We use a 2-dimensional (2-D) Vernier gated-ring-oscillator (GRO) time-to-digital-converter (TDC) in a cascade structure (MASH), so that a larger raw quantization step can be allowed without sacrificing the final resolution performance. The 2-D approach effectively reduces the latency time under a large input, while the MASH structure provides a 2^nd-order noise shaping that produces a lower in-band quantization noise than in a single-stage GRO TDC. The TDC is simulated in a 65nm CMOS process. With the oversampling ratio (OSR) of 20, an equivalent TDC resolution of 2.48ps is achieved under the raw (Vernier) resolution of 56ps. The latency is less than 1/10 of a Vernier TDC´s for a 3ns input signal.