A Low-Power i-ToF LiDAR with Nonlinearity Self-Calibration Technique

This article proposes a low-power 320×240 indirect time-of-flight (i-ToF) vision system with a nonlinearity self-calibration technique. A pump gate modulator (PGM) technique is applied in the pixel to reduce the power consumption of pixel modulation. As a result, the pixel has a higher lateral electric field in a lower voltage swing of modulation, and the pixel can operate in the depletion state to achieve smaller load capacitance. To improve the nonlinearity of the sensor, nonlinearity self-calibration techniques are proposed. It includes the channel toggle technique and predistortion single-slope analog-to-digital converter (SS-ADC), which eliminates the quadratic nonlinearity in the readout channel and source follower (SF) nonlinearity in the pixel, respectively. Furthermore, it reduces the difficulty of nonlinear calibration of different batches of chips. The measured nonlinearity decreases greatly without back-end calibration, which is smaller than 0.8% within the distance range from 0.12 to 5 m. The receiver chip is fabricated in a 110-nm front-side illuminated (FSI) process with a 5.6×5.6 μm pixel size. The chip power is only 130 mW.