A 52 ps resolution ILO-based time-to-digital converter array for LIDAR sensors

摘要

Light detection and ranging (LIDAR) systems offer fast detection and high spatial resolution for imaging and mapping in a host of applications, such as robotics, automotive, agriculture, military, and spaceflight. This paper presents a high-resolution LIDAR sensor system-on-a-chip (SoC) prototype containing a 31×2 pixel channel array with the input time-of-flight (ToF) resolved by a 32×1 time-to-digital converter (TDC) array. A novel TDC design employs injection-locked oscillators (ILOs) to both minimize TDC clock distribution power and improve time accuracy. Global PVT variations among the ILOs is calibrated by an on-chip phase-looked loop (PLL) that ensures good circuit reliability over a wide operating range. Fabricated in GP 65 nm CMOS, the 14-bit TDC consumes 788 μW/channel and achieves 52 ps resolution over an 830 ns full-scale range, 37.2 ps <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rms</inf> single-shot precision, 11 ps <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rms</inf> channel uniformity, and DNL/INL of 0.56/1.56 LSB, respectively. This electrical characterization projects that with future integration with stacked-die avalanche photodiodes (APDs) the SoC has the potential for 0.78 cm ranging precision over a 124 meter maximum ranging distance.