TRO: An On-Chip Ring Oscillator-Based GHz Transient IR-Drop Monitor

With silicon technology further scaling, the switching activity is getting more intense in modern designs. The large switching activities together with GHz operation frequency can greatly affect the power integrity by generating IR-drop noises. Excessive IR-drop can cause functional failures such as timing failure, abnormal reset and SRAM flipping. Hence, IR-drop needs to be monitored in-field. However, directly measuring transient IR-drop waveform usually involves high design or equipment cost. This paper presents a low-cost on-chip GHz ring oscillator-based transient IR-drop monitor (TRO). TRO is composed of all-digital elements, and can be easily integrated into existing IC design flow with negligible overhead. Different from traditional transient IR-drop monitors, TRO measures IR-drop waveform width and average in-field, while recovers IR-drop peak, and reconstructs the transient noise waveform during data analysis or customer return, which eliminates the need for custom circuits or high frequency sampling clock. Simulation results show that TRO is sensitive to IR-drop with peak and width larger than 100 mV and 1.0 ns, which is suitable for GHz IC monitoring. The IR-drop noise width detection resolution can reach 0.125 ns and higher under the help of the proposed edge detector, with noise peak and width measurement error rate less than 6.8% and 9.0%, for 97% of the Monte Carlo samples considering process variations. According to the results and analyses, TRO is also able to trigger quick adaptation within one clock cycle.