A Low Walk Error Analog Front-End Circuit With Intensity Compensation for Direct ToF LiDAR

An analog front-end (AFE) circuit comprising an amplifier module, a peak detector, and a timing discriminator has been designed to facilitate the target identification for direct time-of-flight (dToF) LiDAR. The amplitude saturation error (ASE) is compensated in this article for the intensity determination, which is conducted based on the combination of the pulse width and peak detector. Together with the improved walk error compensation scheme, the proposed AFE circuit can attain the distance and intensity information simultaneously with lower cost and larger dynamic range. A specific frequency compensation method is proposed with a shunt feedback TIA, which improves the stability and mitigates the impact of the package parasitics. The measured -3-dB bandwidth, transimpedance gain, and the input-referred noise current are 281 MHz, 86 dB Omega, and 4.68 pA/root Hz respectively. The proposed AFE circuit, which is fabricated in 0.18 mu m CMOS technology, achieves the distance accuracy of +/- 30 ps and the intensity accuracy of +/- 4% in the dynamic range of 1:5000 without gain control scheme.