Research On Multi-Channel High Performance Analog Front End Integrated Circuit For DToF LiDAR

LiDAR(Light Detection and Ranging)is widely used in the field of industry and military,say remote sensing and precision guidance.With the development of the laser and IC technology,miniaturized laser device and highly integrated LiDAR system have gained more attention in applications of autonomous driving,intelligent robots,and consumer electronics.LiDARs using analog front-end(AFE)circuit can attain the distance information with single shot measurement,and it features the simple back-end processing unit,the system level design of which can be categorized into single channel,linear array,and flash LiDAR.The conventional AFE circuit typically consists of several discrete devices,suffering low integration level.Moreover,the existing AFE circuit cannot obtain the distance and intensity information simultaneously within a large dynamic range.Generally,the conventional linear-mode LiDAR utilizes p-i-n or APD as the photodetector,which is implemented in dedicated process and cannot be monolithically integrated with the AFE circuit.The 3-D integration technology may solve the problem,whereas it is costly and large-scale employment is limited.The research on the AFE circuit of the pulsedToF LiDAR is conducted in this dissertation.Firstly,we introduce the characteristics of the photoelectric detection system and analyze the statistic model of the SPAD,and the performance parameters of the dToF LiDAR and the key techniques of the AFE circuit are illustrated.Secondly,a low walk error AFE circuit with intensity compensation for pulsedToF LiDAR and an analog-SiPM based receiver with intensity output are proposed.Finally,a 16-channel LiDAR system is presented and the 3-D imaging measurement results are illustrated.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 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 proposed AFE circuit is fabricated in 0.18?m CMOS technology.The measured-3-dB bandwidth,transimpedance gain,and the input-referred noise current of the TIA are 281 MHz,86 dB?,and 4.68 p A/?Hz,respectively.The proposed AFE circuit achieves the distance accuracy of±30 ps and the intensity accuracy of±4%in the dynamic range of 1:5000 without gain control scheme.An analog-SiPM based receiver with intensity output is proposed for direct ToF LiDAR,which is designed in standard CMOS technology and monolithically integrated.The analog-SiPM comprises a 16×32 single photon avalanche diodes(SPADs)array with a 25%fill factor.The active quenching and active recharge(AQAR)circuit is utilized in SPAD,effectively reducing the dead time and afterpulsing probability.A novel fully differential pixel read out(FD-PR)circuit is presented within the pixel cell to facilitate the integration with the subsequent TIA,and the nonuniformity of the multiplication factor of the SPAD is improved.The multipath feedforward compensation(MFC)technique is introduced with the TIA to improve the stability and achieve a wider-3-dB bandwidth.The adder array is used in this design to attain the intensity information for the walk error compensation and target identification.The proposed receiver,which is fabricated in 0.18?m HV-CMOS technology,achieves a-3-dB bandwidth of 420 MHz and the input-referred noise current is153 nA_rms.The compensated walk error is less than±0.4 cm and the relative error of the intensity measurement is less than 3%.The distance precision of 7 cm is attained within a detection range of 65 m under the condition of 5 klux ambient light.A 16-channel LiDAR system is presented in this dissertation.A 16-channel LiDAR receiver chip(XTP16)and a 32-channel TDC chip(XTD32)are utilized as the circuit system of the LiDAR receiver.The PLL is used in TDC for improving the robust under various PVT conditions.An interpolator is utilized to promote the TDC resolution and a synchronization scheme is proposed,which eliminates the potential misalignment error.XTP16 and XTD32 are both fabricated in 0.18?m HV-CMOS technology.The measurement results shows that the DNL of XTD32 is+0.27 LSB/-0.25 LSB and the INL is 0.8 LSB_rms.Finally,the 3-D imaging measurement is conducted in the indoor scenery and a frame rate of 10 fps is achieved.