A 103.8-dB DR 25ps-to-35ns Resolution Time-to-Digital Converter with Dynamic Ring Oscillator for LiDAR Applications

As interest in autonomous driving increases, so does the demand for LiDAR sensors. However, a significant challenge for such a sensor is to achieve both a long distance range and high resolution. The required distance range is about 250 m, and the required resolution at close distance is about 2 cm, so a dynamic range (DR) of more than 80dB is required [1, 2]. The fine resolution at close range is important for safety, but not necessary for objects that are far away. Therefore, the work in [1] uses different types of converters depending on the distance: a time-to-digital converter (TDC) is used only for short ranges (<25m) and an additional analog-to-digital converter (ADC) is used for long ranges (>25m). However, since it uses two types of converters, it has low area efficiency and high complexity, which would impose significant overhead, especially for multi-channel LiDAR sensors. This issue can be addressed in [2] by sharing the hardware (VCOs) between two converters. However, each converter requires different specifications on target ranges and it also requires additional effort to process the data from two converters.