Design Of Bionic Dynamic Vision Sensor IC

Image sensor technology has gone through tube and CCD image sensors,and has developed into CMOS image sensors and dynamic vision sensors.With the development of CMOS process,CMOS image sensors have become major technique in image sensors today due to their high performance such as high resolution,high integration,and high speed.However,CMOS image sensors have disadvantages such as large data volume and the need for exposure.Dynamic vision sensors(DVS)is developing rapidly,as a new generation of image sensing technology.This paper designed a DVS,which imitates the ability of higher biological retinal systems to perceive changes in light intensity.The DVS converts the changes of light intensity into pulse signals that can be received by human's brain to determine the characteristics of environmental changes.A bionic dynamic vision sensor chip is designed with real-time scene changes.The advantages of dynamic response,sparse image,and high response speed can be widely used in fields such as the target tracking of high-speed moving object,industrial automation,and robot vision.The chip is composed of a pixel circuit,a wire or circuit,an arbitration circuit and an encoding circuit.The pixel circuit realizes the conversion of optical signals to electrical signals,and the wire or circuit,the arbitration circuit and the encoding circuit realize the asynchronous communication through the Address Event Representation(AER).The pixel unit circuit uses a photodiode to convert an optical signal into an electrical signal,amplifies the electrical signal via a switched capacitor amplifier,and produces an event signal that reflects whether the light intensity becomes stronger or weaker through a threshold comparator.The event signal generates a request signal to the outside of the pixel through a logic circuit.The request signal of the single pixel unit is sent to the arbiter through a line or circuit after the matrix arrangement.After the arbiter arbitrates,it controls the encoding circuit to generate the encoded signal of the pixel unit,and transmits the pixel encoded signal to the outside of the chip through a handshake protocol.This chip uses a novel DVS pixel unit.In the I/V conversion part,two MOS working in the subthreshold region are connected in series to increase the contrast sensitivity.Negative feedback is used at the inverting end of the photodiode to ensure that its reverse voltage is relatively stable,and the ON / OFF event judging circuit is designed in the logic part to monitor the attributes of the event.The chip uses a two-input average arbitration unit to build a row and column arbiter.This ensures the priority order of the request signals of each pixel unit is kept relatively average,and a fairer pixel processing is achieved when multiple pixels request simultaneously.This paper uses Spectre software in Cadence to simulate and verify each sub-module circuit and the overall circuit of the chip based on the XFAB 0.18 um 1P6M CIS process.The layout design,post-simulation and test board design were conducted based on the 32*24 pixel overall circuit.The final simulation results show that the dynamic range of this chip is about 100 d B,the contrast sensitivity is about 40%,and the fill factor is about 13%.And the functions and specifications of the chip can meet the requirements of the design.