A radiation-hardened-by-design technique for improving single-event transient tolerance of charge pumps in PLLs

Abstract

A radiation-hardened-by-design (RHBD) technique for phase-locked loops (PLLs) has been developed for single-event transient (SET) mitigation. By presenting a novel SET-resistant complementary current limiter (CCL) and implementing it between the charge pump (CP) and the loop filter (LPF), the PLL's single-event susceptibility is significantly decreased in the presence of SETs in CPs, whereas it has little impact on the loop parameters in the absence of SETs in CPs. Transistor-level simulation results show that the CCL circuit can significantly reduce the voltage perturbation on the input of the voltage-controlled oscillator (VCO) by up to 93.1 % and reduce the recovery time of the PLL by up to 79.0%. Moreover, the CCL circuit can also accelerate the PLL recovery procedure from loss of lock due to phase or frequency shift, as well as a single-event strike.