All-Digital Ring-Oscillator-Based Macro for Sensing Dynamic Supply Noise Waveform

This paper proposes an all-digital measurement circuit called a ldquogated oscillatorrdquo to capture the waveforms of dynamic power supply noise. An improved gated oscillator with a power-gating structure is also proposed. The gated oscillator is constructed using standard cells, and thus is easily embedded in SoCs. Its performance was evaluated using test chips fabricated in a 90 nm process. The gated oscillator achieved 5.3-5.9 Gsample/s with an area of 10.08 times 6.72 mum
²
, and the improved power gating structure achieved 6.6-8.3 Gsample/s in a 90 nm process. The characteristics of the gated oscillator and related design issues are also discussed. These characteristics were verified on silicon. We evaluated the effect of the decoupling capacitance based on measurement results obtained using the gated oscillator, and demonstrated that it could be used to verify power integrity.