A Single-Event-Hardened Scheme for Ring Oscillator Applied to Radiation-Resistant PLL Microsystems

A voltage-controlled oscillator (VCO) is one of the key modules of the phase-locked loop (PLL) microsystem, and it is easy to bombard using high-energy particles in a radiation environment, resulting in the single-event effect. In order to improve the anti-radiation ability of the PLL microsystems used in the aerospace environment, a new voltage-controlled oscillator hardened circuit is proposed in this work. The circuit consists of delay cells with an unbiased differential series voltage switch logic structure with a tail current transistor. By reducing sensitive nodes and using the positive feedback of the loop, the recovery process of the VCO circuit to the single-event transient (SET) is reduced and accelerated, so as to reduce the sensitivity of the circuit to the single-event effect. The simulation results based on the SMIC 130 nm complementary metal-oxide-semiconductor (CMOS) process show that the maximum phase shift difference of the PLL with the hardened VCO is reduced by 53.5%, which shows that the hardened VCO structure can reduce the sensitivity of the PLL to the SET and improve the reliability of the PLL in the radiation environment.