Simulation of transient dose rate effect on analog phase locked loop

The transient dose rate effect (TDRE) on analog phase locked loop (PLL) is presented in this paper. New TDRE models of NMOS and PMOS are proposed through the combination of SPICE and Sentaurus TCAD, which improve a previous modeling method and especially incorporate the effects of the Length/Width ratio of transistors, resistance network of the substrate, and bias condition of contacts. The primary photocurrents in TDRE models, calculated by TCAD, are successfully fitted by double-exponential functions. Firstly, the TDRE of each PLL's sub-circuit is simulated. Then, the global effect of the PLL is simulated and the coupled relationship among sub-circuits is analyzed. Simulation results indicate that the current-based charge pump and voltage-controlled oscillator are sensitive to TDRE, and there is a significant coupled relationship between the two sub-circuits. On the contrary, the phase frequency detector shows low sensitivity to TDRE. Lastly, as two Radiation-Hardened-By Design (RHBD) methods, using the voltage-based charge pump and using the voltage-controlled oscillator with a large drive current are proved to be effective in improving the TDRE of PLL.