Single-Event Effects Characterization of LC-VCO PLLs in a 28-nm CMOS Technology

Two-photon absorption laser experiments are conducted on a low-jitter tunable hybrid analog-digital LC-tank phase-locked loop (PLL) in a 28-nm bulk CMOS technology. The single-event effect (SEE) sensitivities for different blocks as well as the effect of varying circuit parameters are analyzed. The analog loop filter and the inductor-varactor area in the voltage-controlled oscillator (VCO) LC tank are identified as the most sensitive areas of the PLL, which generally agrees with previous studies. The VCO tail common-mode node, which was previously shown to be highly sensitive to SEE, exhibits very good robustness, thanks to the proposed second-order harmonic LC tail filter added in this design. The laser experiments show that a lower PLL bandwidth tends to reduce the SEE sensitivities of the PLL, while the results on the effect of the VCO frequency are mixed and need further study.