Multi-Channel LADAR Readout Circuit Based On Linear-Mode APD

Laser Detection and Ranging(LADAR)based on linear-mode avalanche photodiode(APD)has the advantages of fast response time and high sensitivity.It is widely used in the fields of unmanned aerial vehicles,3D imaging,vehicle assisted driving,and so on.The traditional LADAR readout circuits adopt discrete device design,which have the problems of high cost,large volume and poor integration.In order to realize high-speed,high-precision and single-chip signal processing of LADAR systems,the research of multi-channel LADAR readout circuit has great significance.In order to meet the application requirements of multi-channel LADAR system integration,a 32-channel readout circuit with high-gain,high-bandwidth and low-noise is designed in this paper.Multi-channel configurable technology is used to optimize overall power consumption.Firstly,a novel three-stage analog front-end(AFE)circuit architecture is proposed,including a variable gain transimpedance amplifier(TIA),a differential voltage amplifier and an analog equalizer.The high-gain TIA adopts the shunt-feedback topology to optimize the noise performance.The voltage amplifier increases the gain and uses the source-degeneraded resistor to achieve gain variation.The equalizer uses capacitive degeneration technique to boost the channel bandwidth,and integrates a 6-bit current digital-to-analog converter(DAC)to produce a built-in threshold voltage.Based on the AFE circuit,pulse signal detection module of the LADAR readout circuit have been designed,including automatic gain control(AGC),channel selector,peak detector and dual-threshold timing discriminator,which improve the adaptability of the readout circuit and meet the multi-channel LADAR detection requirements based on time-of-flight(TOF).The 32-channel AFE chip is fabricated with SMIC 0.18-?m CMOS technology.The core area of chip is about 3.1 mm×1.1 mm.The measurement results show that the transimpedance gain of the circuit varies from 65 dB to 101.6 dB.In the highest gain configuration,the channel bandwidth is 190 MHz,which can respond to a narrow pulse signal with 5 ns pulse width.The input noise current spectral density is 2.6 pA/?Hz.The maximum output voltage swing is greater than 1000 m V,and the linear dynamic range reaches 64 dB.The minimum detectable current achieves 0.4 ?A with SNR=10.The power consumption per channel is 37 mW from a single 3.3 V supply.