Temperature- and aging-resistant inverter for robust and reliable time to digital circuit designs in a 65nm bulk CMOS process

Inverters are one of the most basic logic blocks and 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 oscillators and time to digital converters, both temperature dependencies have to be considered. This work introduces a circuit design for a robust and resilient inverter and an analysis on its temperature-dependent aging characteristic. The implemented inverter is driven by a common-source amplifier to achieve high robustness against temperature variation and aging effects. Based on this, circuit designs for a ring oscillator and an inverter-based delay line for a time to digital converter has been implemented. The results show that the deviation of the delay for an inverter can be minimized from 13.2% for conventional inverter design to less than 2% for the temperature-and aging-resistant design over a wide temperature range from -40° C to 150° C and a stress time of ten years.