Research On Key Technology Of Charge Pump Phase Locked Loop Circuit Of Anti-radiation CMOS Image Sensor

CMOS image sensors working in a radiation environment are susceptible to being bombarded by high-energy particles to produce single event transients(SET),causing errors in the output clock frequency and phase,and seriously affecting the stability of the overall circuit of the CMOS image sensor.The phase locked loop is the clock circuit of the CMOS image sensor.The radiation hardening research of the phase locked loop circuit is very important for the stable operation of the CMOS image sensor in the radiation environment.The main work and innovations of this paper include:First,a low mismatch charge pump phase-locked loop circuit is designed.According to the design requirements,the relevant loop parameters are determined,and circuits such as a phase-frequency detector without dead zone effect,a charge pump with low mismatch,a low-noise voltage-controlled oscillator,and a 32-frequency divider working at high frequencies are completed.Using SMIC 180 nm rf CMOS process to simulate the designed charge pump phase-locked loop,the results show that when the designed effective output voltage of the charge pump is 0.25V～1.5V,the current mismatch is only 0.75% and the voltage deviation is 0.5%.The output range of the VCO is 0.8GHz～1.7GHz,and the phase noise at 1MHz is-102 d B when the output is 1.7GHz.When the input signal is 50 MHz,the output clock is 1.6GHz,the system lock time is 2.5μs,and the control voltage ripple is only0.5m V.Secondly,the Sentaurus TCAD tool is used to establish a circuit-level simulation pulse current model of SET when the linear transmission energy(LTE)is 100 Me V·cm^2/mg.To traverse all the nodes of the charge pump phase-locked loop designed in this paper,find the sensitive nodes of each module and the overall circuit.It is verified by simulation that the phase-locked loop is the most sensitive module of the entire circuit to SET radiation,and the SET sensitive node in each module is determined,which provides a theoretical basis and reinforcement ideas for the anti-radiation reinforcement design.Finally,the anti-SET radiation hardening design is carried out on the charge pump phase-locked loop.According to the simulation results of SET sensitive nodes of each module,a corresponding reinforcement scheme is proposed for each module.Among them,the frequency discriminator adopts the combination of D trigger and DICE to design anti-SET D trigger.A method to increase the switch path is proposed for the charge pump circuit to reduce the influence of SET irradiation.The frequency divider adopts the method of three-mode redundancy for reinforcement.Because the VCO adopts the delay unit of the differential series voltage switch logic(DCVSL)structure,the DCVSL above third order can eliminate the influence of SET,and no reinforcement is needed.The results show that the circuit after strengthening reduces the sensitive nodes before strengthening,the recovery time is also greatly shortened,and the deviation of the maximum control voltage in all nodes is reduced to7% of that before strengthening.The performance of the reinforced phase-locked loop circuit is simulated,and the results show that the performance of the reinforced circuit is basically equivalent to that before the reinforcement.