A Ring Oscillator based reliability structure for duty-cycle measurement under BTI stresses

The static BTI stress (DC stress) have a significant influence on duty cycle of Ring Oscillators, low power SRAMs and dynamic register files because of its asymmetrical gradation. A ring oscillator based structure is proposed to measure the duty cycle of an inverter chain based ring oscillator. The proposed structure can measure the duty cycle shifts conveniently and accurately. Simulating results shows that benefiting from the continuous accumulation, the duty-cycle of the inverter chain can be measured accurately.