The Design Of A 4-channel 12-bit High-voltage And Anti-radiation DAC

With the rapid development of national space industry,more and more electronic systems work in the outer space for operation,which caused that extensive attention has been paid to the effects of radiation induced by outer space radiation environment on the chip.As some integrated circuits or integrated systems work in outer space all the time,which results in increasing demand for integrated circuits or integrated systems with several operating voltages and anti-radiation.Therefore,the high reliability and long life of the space exploration integrated system has become the current hot research direction.Digital-to-Analog Converter(DAC)is widely used in medical instrumentation,industrial control,digital communications,scientific and aerospace instrumentation,power control,servo control,and other avionics fields.The digital-to-analog converter is an essential circuit in an integrated system such as a serial circuit and an outer space detection system.Therefore,designing an anti-radiation digital-to-analog converter(DAC)ensures that space-based data is properly stored and transmitted.This paper focuses on the following aspects of work:1)The related irradiation damage mechanism is described,and the reasonable LDMOS(Dongbu HiTek BCD 0.18?m)is chosen to balance the difficulty of design between high-voltage and irradiation.The design meet the two irradiation requirement:100Krads(TID),80MeV·cm~2/mg(SEL).2)Poly-silicon resistor is chosen to complete the design of the DAC chip with the read-back function.A kind of level shifter is designed to deal with the difficulty that the digital working voltage is always 5V while analog is wide supply voltage(three voltage mode:±15V,±5V,0~5V)so that the whole DAC chip can work well.For poly-silicon resistor,the resistance decoding circuit is designed to ensure the correctness of signal conversion.The minimum DNL of the DAC chip in the three voltage mode is-0.35LSB,and the range of INL is controlled within(-0.6~+0.2)LSB.3)Considering the influence of the voltage and environment on the polycrystalline resistor,the proportion of resistance in the R-2R decoding circuit is destroyed.Through the analysis of the Monte Carlo simulation of the decoding circuit,the resistance trimming circuit is designed to adjust the resistance of the high 4 bit(D8-D11),further to ensure the accuracy of the R-2R resistor decoding.4)Using Cadence ADE,each module and the overall DAC circuit simulation and layout planning are finish of the DAC chip,at the same time the simulation data are analyzed to determine the signal conversion error.Ensure that the DAC circuit can work correctly and effectively in±15V,±5V,0~5V three voltage modes,and the accuracy is guaranteed.Ultimately the layout area of DAC chip is determined to be 5.8mm×5.5mm.Based on the work above,this paper introduces the principles of the design of irradiation digital to analog converter,the problems encountered in the design of the circuit and the layout,and the related solutions.