A time-to-digital converter (TDC) often consists of sophisticated, multilevel, subgate delay structures, when time intervals need to be measured precisely. The resolution improvement is rewarding until integral nonlinearity (INL) and random jitter begins to limit the measurement performance. INL can then be minimized with calibration techniques and result postprocessing. The TDC architecture based on a counter and timing signal interpolation (the Nutt method) makes it possible to measure long time intervals precisely. It also offers an effective means of improving precision by averaging. Traditional averaging, however, demands several successive measurements, which increases the measurement time and power consumption. It is shown here that by using several interpolators that are sampled homogeneously over the clock period, the effects of limited resolution, interpolation nonlinearities, and random noise can be markedly reduced. The designed CMOS TDC utilizing internal systematic sampling technique achieves 3.0-ps root mean square (RMS) single-shot precision without any additional calibration or nonlinearity correction. Index Terms-Averaging, CMOS, delay-locked loop (DLL), integral nonlinearity (INL), jitter, Nutt method, quantization error, time interval measurement, time-to-digital converter (TDC). I. INTRODUCTION A TIME-TO-DIGITAL converter (TDC) measures the time interval between two or more timing signals and presents the result in digital form. For the sake of simplicity, the timing signals are often called start and stop signals. High precision TDCs are used in many applications, such as laser distance measurement [1], [2], high energy physics [3], [4], timing parameter verification of high-speed circuits and components [5], [6], medical imaging [7], [8], single-photon detectors [9], [10], and Raman spectroscopy [11], [12]. The use of TDC techniques is increasing as traditional analog signal processing is challenged by modern scaled IC-circuit technologies, which favor signal processing in the time domain. The critical analog circuit blocks can be often replaced with a TDC-based architecture in all-digital PLLs [13], [14] and in analog-to-digital conversion (ADC) [15], [16], for example.