Radiation-Tolerant All-Digital PLL/CDR with Varactorless LC DCO in 65 nm CMOS

This paper presents the first fully integrated radiation-tolerant All-Digital Phase-Locked Loop (PLL) and Clock and Data Recovery (CDR) circuit for wireline communication applications. Several radiation hardening techniques are proposed to achieve state-of-the-art immunity to SingleEvent Effects (SEEs) up to 62.5 MeV cm$^{2}$ mg$^{−1}$ as well as tolerance to the Total Ionizing Dose (TID) exceeding 1.5 Grad. The LC Digitally Controlled Oscillator (DCO) is implemented without MOS varactors, avoiding the use of a highly SEE sensitive circuit element. The circuit is designed to operate at reference clock frequencies from 40 MHz to 320 MHz or at data rates from 40 Mbps to 320 Mbps and displays a jitter performance of 520 fs with a power dissipation of only 11 mW and an FOM of −235 dB.