Research On Design Of Radiation Hardened High Voltage Analog Switch

High-voltage analog switch chips,considered as a bridge to connect analog signals with digital signals,are widely used in digital-analog control parts of various satellites and other aerospace systems.However,the current analog switches available in the market cannot adapt to such environments as high radiation in space etc.Therefore,it is of great significance to research on radiation harden of high-voltage analog switches.When CMOS integrated circuits are used in space environment,variety of radiation effects by radiation will happen,and the typical representatives are total ionizing dose and single event effect.Ordinary circuits affected by radiation will have problems such as logic function errors and increased current leakage.For high-voltage analog switching circuits,the high breakdown voltage of the circuit means that the thickness of the gate oxide of the device is large,which is related to the threshold drift of the device under the total ionizing dose effect.The increase in thickness will result in a rise in the space charge generated in the oxide layer after irradiation,which will further increase the threshold drift of the device after being irradiated.The worst case could be that the original enhanced NMOS tube becomes a depleted one,causing the function failure of the circuit.To solve this problem,this paper first develop a radiation harden by design of gate oxide of the device,based on the SOI CMOS process.And it will be ensured that the breakdown voltage and device isolation after strengthening the gate oxide against radiation still meet the design requirements and that device under irradiation is reliable.After that,based on the device characteristics after radiation harden by process and different sensitivity of each circuit module to different effects of radiation,different methods of radiation harden are carried out for different modules to resist the total ionizing dose and the single event effect.Aiming at the problem that the threshold drift caused by irradiation will cause the reference level to drift,a new method of radiation compensation circuit is designed to reduce the influence of irradiation on the reference voltage and improve the anti-radiation ability of the reference circuit.Then,a single event reinforcement design is carried out on the latch decoding module to ensure the stable function of the digital module in a single event upset event.Because the device adopts SOI CMOS process,the occurrence of anti-single event latch-up effect is physically eliminated.Finally,the layout of the chip is drawn and the taped-out chip is tested for radiation and circuit performance.According to the test results,the maximum on-resistance of the final chip at room temperature is 129.1?;the maximum leakage current 44 n A;the maximum transmission delay time 278.9ns;the maximum power supply current 0.6m A;the total resistance dose(TID)?100krad(Si)and the singleevent latch-up(SEL)?75Me V·cm2/mg.All design indexes meet their requirements.