Effects of technology scaling on the SET sensitivity of RF CMOS voltage-controlled oscillators

We analyze single-event transient (SET) effects in a high-speed voltage-controlled oscillator (VCO) design that is applicable to mixed-signal RF operations. Our study shows that the sensitivity of this type of circuit topologies exhibits a strong correlation to: the minimum feature size of the technology in use, the range of oscillating frequencies that the circuit is designed to achieve and the frequency at which the VCO is operating. We also determine that current-starved VCOs have an optimal functional range for improved radiation tolerance, located at the upper segment of their voltage-to-frequency transfer characteristic, where exposition to low LET ions become of no consequence on the operation of the circuit. More importantly, we show that derating the frequency of such VCO designed in a state-of-the-art technology does not compensate for the increased radiation vulnerability at that node. If not properly accounted for, the performance overhead that the newer technology provides is shown to severely penalize the radiation hardness of the circuit.