Research On The Delay Model Of Cell Circuit In Near-threshold Domain

With the development of low-power technologies,the design of near-threshold circuits with energy efficiency advantages has received widespread attention.And cell circuit delay model is of great significance for the timing analysis.The establishment of the near-threshold cell circuit delay model faces two challenges.Firstly,the input slew causes the delay nonlinearity.Secondly,the cell delay in near-threshold domain follows a non-Gaussian distribution.Therefore,it is necessary to establish a fast and accurate near-threshold cell delay model.In the above background,the cell delay models in near-threshold domain for inverter,stacked structure and parallel structure considering the input slew are established.For the nominal cell delay model,models for extremely fast input and fast input are established by the segmented effective current based on the simulation results,and model for slow input is established by fitting the simulation results.The inverter statistical delay model is established based on the nominal delay model and the log-skew-normal distribution.Then the binary Taylor expansion is used to solve multivariate threshold voltage fluctuation problem in the stacked structure.And the exponential approximation is used to solve the problem of multivariate current fluctuations in the parallel structure.Thereby statistical delay models of the stacked structure and the parallel structure are established.The proposed cell delay model is verified under SMIC40 nm process with inverters,NAND gates and NOR gates employed.The results show that,compared with Monte Carlo simulation,the error of the nominal cell delay in this thesis is less than 10.78%,and the error of variance and ±3? value are both less than 19.34%.Compared with the nominal delay model based on the one-point effective current,the nominal delay of the inverter,stacked structure and parallel structure are increased by 3.10 times,2.97 times and 2.73 times,respectively.Compared with the statistical delay model based on the multivariate threshold voltage equivalence and multivariate current moment equivalence,the accuracy of the inverter delay variance,+3? value and-3? value is increased by 1.78 times,1.23 times and 2.27 times,respectively.The variance accuracy of stacked structure and parallel structure is increased by 2.02 times and 1.19 times,+3? value accuracy is increased by 1.69 times and 6.80 times,-3? value accuracy is increased by 1.68 times and 19.56 times.