Research On Lidar Analog Front-End Circuit Based On Liner Mode APD

In recent years,lidar has been rapidly applied in digital city,autonomous driving,electronic products and other emerging fields.Lidar based on linear mode APD is still the mainstream technology system of lidar due to its simple principle and no dead zone time.As a key module in the lidar system,the analog front-end receiving circuit needs to be analyzed and designed.Aiming at the miniaturized MEMS lidar which is in urgent need in the market,the design goal of analog front-end circuit is formulated in combination with the application requirements and theoretical basis.Then,based on TSMC 0.18um CMOS technology,this paper completed the design of lidar analog front-end circuit system,which mainly includes transresistance amplification module,time identification module and peak value acquisition module.A new Regulated common source common gate(RGC)preamplifier is used in the transresistance amplifier module.Compared with the traditional structure,the power consumption is reduced and the gain bandwidth of the circuit is increased.The pseudo-difference structure is adopted to reduce the common mode interference of the circuit.The rear differential amplifier has a three-stage gain mode,which can be adjusted by external signal control to improve the input dynamic range.The time identification module adopts the double-threshold time identification method,which can reduce the walking error compared with the traditional frontier time identification method.The designed highspeed comparator has a smaller input-output delay,and the designed selfbias reference current source based on Cascode structure has a high power rejection ratio of 76.3 dB.Stable bias current can be generated for highspeed comparators.The peak value acquisition module adopts an improved peak value detection holding circuit based on current mirror structure,which has smaller overshoot error and faster response speed.Finally,based on Candence software,the layout of the lidar analog front-end circuit is completed.After the extraction of parasitic parameters,the post-simulation analysis is carried out.The simulation results show that the bandwidth of the transresistance amplification module designed in this paper is 1386MHz under the transresistance gain of 63dBΩ,475MHz under the transresistance gain of 92dBΩ,and 222MHz under the transresistance gain of 121dBΩ.The corresponding 62dB input dynamic range current can support 0.4uA～500uA,the equivalent input noise is 8.74 pA/(?),and the power consumption is less than 50mW,which meets the design target.The precision of the designed time identification module is high.After compensation,the maximum walking error is 0.27ns,which is converted to the actual ranging error of 4.05cm.