Degradation and Temperature Analysis of Voltage-Controlled Ring Oscillators for Robust and Reliable Oscillator Designs in a 65nm Bulk CMOS Process

K. Tscherkaschin, T. Hillebrand, M. Taddiken, S. Paul, D. Peters-Drolshagen (Univ. Bremen, Germany)

Ring oscillators exhibit a strong temperature dependency. Additionally, degradation in CMOS transistors affects the performance of circuits over time and is strongly dependent on temperature during circuit operation. In order to design robust and reliable ring oscillator-based circuits, both temperature dependencies have to be considered. This work introduces systematic analyses on temperature dependencies for different voltage-controlled ring oscillators, which are based on current-starved inverters, and its temperature-dependent aging characteristics. The current-starved inverters are driven either by a common-source amplifier with non-linear control characteristic of the oscillation frequency with regard to input voltage or by a transconductance amplifier with linear control characteristic. The results show that the designer has to prioritise robustness and reliability over linear control characteristic or vice versa.