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This article presents a low-power, all-digital multichannel time-to-digital converter (TDC) for light detection and ranging (LiDAR) sensors. The proposed TDC architecture measures the time interval through a coarse counter, middle, and fine delay line-based interpolation technique (the Nutt method). Automatic calibration by middle and fine all-digital delay-locked loops (ADDLLs) is provided to ensure the stability of the generated time slots. Charge pump, loop filter, and voltage-controlled delay line inside the conventional analog delay-locked loops (DLLs) are replaced by an accumulator (ACC) and digitally controlled delay line (DCDL). This makes the design particularly compact, low power, and suitable for multichannel applications. The presented architecture can generate information for amplitude variation (walk error) compensation. This information is generated by measuring the pulsewidth and position of three successive STOP pulses inside each channel within a single-shot measurement. A low-jitter injection-locked frequency multiplier (ILFM) generates a 625-MHz internal clock signal out of 25-MHz external reference oscillator, which shrinks the number of delay elements to cover one period of the reference clock and improves the precision of the TDC. Operation at higher frequency provides high throughput and short conversion time (less than 3 ns). The three-level TDC offers 13.1- $\mu \text{s}$ maximum input range and 50-ps resolution. The measured DNL and INL of the TDC circuit are 0.47 and 0.71 LSB, respectively. The TDC circuit is implemented in a 180-nm standard CMOS process with a die size of 1.5 mm $\times1.5$ mm. The total power consumption of the multichannel TDC is 87.6 mW. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A high-resolution time-to-digital converter (TDC) was designed and tested. The converter is based on the fundamental method of counting the full clock cycles of a low-phase-noise reference clock and using a single-stage interpolating method employing time-to-amplitude converters that are based on Miller integrators. Counters and other control logic were implemented on a field-programmable gate array, and the interpolation units were constructed using discrete components. The single-shot precision of the uncompensated converter is about 1.8 ps over a time interval range of 0 to 328 \mu\s. Single-shot precision is limited by the nonlinearities of the interpolators. These measurement errors caused by the nonlinearities are systematic, and thus, precision can be improved to 1 ps by a simple integral nonlinearity compensation. Other important factors that contribute to single-shot precision are the N-cycle jitter of the reference clock and the noise generated by the TDC circuit itself. By careful design, these errors can be made small enough to achieve picosecond-level precision. [ABSTRACT FROM AUTHOR]