A 2-D GRO vernier time-to-digital converter with large input range and small latency

The proposed time-to-digital converter (TDC) arranges two Vernier gated-ring-oscillator (GRO) branches in a 2-dimension (2-D) fashion. All delay differences between X phases and Y phases can be used, rather than only the diagonal line. The large latency time inherited from Vernier structure is therefore dramatically reduced. The TDC is implemented in a 90nm CMOS process and consumes 1.8mA from 1.2V. The measured input range can safely cover a full period of a 50MHz sampling signal. With the same delay elements, the latency time is less than 1/6 of that needed in a standard Vernier TDC.