Research And Design Of A Novel Radiation-Hardened Phase-Locked Loop

The booming development of astronautics,aeronautics,and nuclear energy industries requires the improvement of the anti-radiation ability of the electronic systems.Phase-locked loops(PLLs),because of their well-integrated characteristics,outstanding efficiency and various structures,have become the mainstream application in frequency synthesizing and clock recovery.Due to the fact that the PLL directly controls stability of the chip's frequency,its ability to function properly in the radiation environment must be guaranteed.Otherwise,once the PLL is interfered by the radiation,the deviation of the output frequency or phase can cause the clock disorder or the malfunction of the whole chip which will seriously endanger the operation of the system.Especially when it comes to the deep submicron technology,the sensitivity of the transistor to radiation is increased,which makes the radiation tolerance of the chip decrease gradually.Therefore,it is a must to design a radiation-hardened PLL to ensure its performance in the radiation environment.In this paper,the radiation hardening has been studied on the conventional charge pump PLL.The main work is as follow:Starting on the transfer function model,the transfer function of each module has been studied separately and then the frequency domain model of the PLL has been deduced.Subsequently,the change of the transfer function of each module after interfered by the single event transient(SET)has been analyzed in detail.This provides a theoretical basis for subsequent circuit and hardening design.Combined with the transfer function,the specific loop parameters of PLL are explored,and the influence of the change of loop parameters on the overall performance of PLL is analyzed.On this basis,the circuit design and basic performance simulation of each module of PLL are carried out,and the noise characteristics of each module are simulated.Focusing on the charge pump circuit which is most sensitive to SETs,the exploration of the sensitive nodes to SETs is conducted,and a new radiation-hardened charge pump circuit is proposed.Subsequently,detailed simulation has been done to exam the new circuit's performance and anti-SET ability.The results show that compared with the unhardened circuit,the control voltage change of the VCO decreases by 90.1% and the recovery time of PLL decreases by 54% under the influence of the deposited charge of 500 fC.Moreover,the new radiation-hardened charge pump can effectively reduce the clock jitter of the output frequency by 12.5%.Meanwhile,the area penalty is only 36.8%.Compared with the state-of-the-art radiation-hardened charge pump structure,the proposed structure is readily to be implemented and will not change the original loop parameters.Therefore,this structure has excellent universality.In addition to the detailed design of the radiation-hardened charge pump,the VCO and frequency divider which are also sensitive to SETs has also been studied and redesigned.The simulation results show that the number of SET sensitive nodes in the radiation-hardened VCO decreases greatly,only the last stage remain sensitive to the SETs.Meanwhile,although the area of the radiation-hardened frequency divider circuit has increased by 66.7%,the output of the radiation-hardened frequency divider does not shift significantly after the ion strike while the conventional divider suffers a 82.8°phase displacement.