A Novel 550-fs Time-Resolution 7.5-bit Stochastic Time-to-Digital Converter Based on Two Arbiter Groups

This article presents a novel two arbiter groups-based stochastic time-to-digital converter (STDC) to achieve a better linearity and larger measurement range compared to a traditional STDC. Traditional STDCs with one arbiter group have a bad linearity and narrow measurement range, for the nonlinear time-to-digital transfer function that described by a Gaussian cumulative distribution function (cdf). To improve the linearity, a basic two arbiter groups-based STDC is proposed first. Through properly shifting the time-offset distributions of the two arbiter groups away from each other by applying a global time-offset reference to them, a virtual uniform distribution could be formed between the two shifted time-offset mean values. To achieve a large measurement range, a dual-input dual-output periodic signal generator (DIDO-PSG) and a global time-offset setting circuit (GTOSC) are further designed for the proposed STDC to obtain two pairs of time-offset distributions with twice measurements for one input time interval. Through properly setting the mean values of the four time-offset distributions based on GTOSC, an overall transfer function with a large linear part that contributes to a good linearity could be achieved. Finally, a test chip prototype fabricated in a 0.18-
$\mu \text{m}$
CMOS technology demonstrates a 550-fs time resolution and a 0.105-ns measurement range with −1.81-LSB integral non-linearity (INL) at 50 MS/s, which is much better than traditional STDCs.