Design Of Monolithic Integrated Light To Frequency Converter Circuit

As a signal carrier,light belongs to analog signal,which cannot be directly processed by computer and needs to be converted into digital signal.The traditional analog signal is converted into digital signal without analog/digital converter,but this method is expensive,large power consumption.Therefore,the direct conversion of optical signals into digital signals has gradually received attention.The light to frequency converter(LFC)circuit converts an optical signal into an electrical signal that can be used for detection in the form of a square wave,whose Frequency is in a linear relationship with Light intensity.There are still many technical problems in the development of this circuit,such as the control of low dark current and low nonlinearity,the improvement of accuracy,and the reduction of the cost of producing a single chip,which limit the commercial application of this type of product.On the same silicon substrate is presented in this thesis a kind of high linearity,low power consumption,low dark signal frequency of monolithic integrated light-frequency converter circuit,the circuit is mainly composed of PN photodiode,capacitive feedback transimpedance amplifier(CTIA),integral charge discharge circuit,comparator circuit,oscillator circuit of the five modules.In terms of performance,the maximum output frequency of the circuit is not less than 1.0mhz,the output duty ratio is50%square wave,the error is less than or equal to 5%,the nonlinear error is less than or equal to 1%,the conversion gain is not less than 400 Hz/(?W/cm~2)under the wavelength of 530 nm,and the dark signal frequency is less than or equal to 1 Hz.These performance parameters are not much different or even exceed those of the foreign industrial grade commercial chip TSL237.The research work of this thesis mainly includes the following three aspects:1.Completed the design of monolithic integrated optical to frequency conversion circuit.According to the performance parameters of the circuit are given to build circuit architecture,and the photodiode,CTIA circuit and integral charge discharge circuit,comparator circuit,oscillator circuit,unit module for the design and simulation,finally by putting together for the whole circuit simulation module series,also studied the integration capacitor,the influence of the discharge capacitance on the circuit performance.2.Completed layout design and post-simulation.This thesis introduces the principle and rules involved in layout design,completes the corresponding layout design according to the built circuit,extracts the parasitic parameters of the designed layout after the layout passes the verification,and finally carries on the post-simulation verification results.3.The chip test of the flow chip was completed and the results were analyzed.By building a test platform to test the chip sample of the wafer,performance parameters such as duty cycle maximum output frequency,nonlinearity,dark signal frequency were obtained.The test results were analyzed,and possible solutions were proposed for the shortcomings of unstable output frequency.In this thesis,the design of monolithic opto-frequency conversion circuit is finally completed,and the flow chip is realized on 0.6?m CMOS process,and the chip test is completed.Finally,the test performance of the sample chip from the flow chip is 54.6%duty cycle,the maximum output frequency is 1.005 MHz,the nonlinearity is 0.42%,the conversion gain is 2190 Hz/(?W/cm~2),and the dark signal frequency is less than 0.1 Hz.