DSC-TRCP: Dynamically Self-Calibrating Tunable Replica Critical Paths Based Timing Monitoring for Variation Resilient Circuits

In situ timing monitoring of critical paths (CPs) can help eliminate the excess timing margin but suffer from miss detection risk because the CPs might not be activated. However, indirect monitoring methods encounter discrepancies between the replica circuit and the actual circuit due to calibration challenges in the replica circuit. We propose a dynamically self-calibrating tunable replica CP (DSC-TRCP)-based adaptive voltage scaling (AVS), which integrates the advantages of both in situ and indirect monitoring methods while overcoming their disadvantages. Our TRCP is dynamically calibrated to follow the selected CPs. We also propose a low-overhead, low-latency timing monitor (called Mini-Razor) inserted at the half-path point to cooperate with TRCP to monitor the timing of the main circuit. Applied on a binary neural network (BNN) accelerator and implemented in a 28-nm CMOS technology, the maximum calibration error between DSC-TRCP and actual CPs does not exceed 2.1% under different process, voltage, and temperature (PVT) variations. Operating at 31 MHz and 0.55 V, the chip provides a 58% reduction in power consumption with only a 0.65% increase in area cost and offers up to 232% frequency gain in the near-threshold region. Our DSC-TRCP achieves high AVS gains with low costs and ensures the effectiveness of monitoring.