Hot carrier effects on jitter performance in CMOS voltage-controlled oscillators

The effects of hot carrier stress on CMOS voltage-controlled oscillators (VCO) are investigated. A model of the threshold voltage degradation in MOSFETs due to hot carrier stress has been used to model jitter in voltage-controlled oscillators. The relation between the stress time which induces the hot carrier effects due to generation of interface traps near the drain of the n-MOSFETs, and the degradation of the VCO performance is presented. The VCO performance degradation takes into consideration decrease in operation frequency and increase in jitter. The experimental circuits have been designed in 0.5 mu m n-well CMOS technology for operation at 3 V. Experimental results show that after four hours hot-carrier stress the jitter is increased by 40 ps for single-ended current starved VCOs.