Canary Replica Feedback for Near-DRV Standby VDD Scaling in a 90nm SRAM

Canary bitcells act as online monitors in a feedback architecture to sense the proximity to the data retention voltage (DRV) for core SRAM bitcells during standby voltage scaling. This approach implements aggressive standby V_DD scaling by tracking PVT variations and gives the flexibility to tradeoff between the safety of data and decreased leakage power. A 90 nm 128 Kb SRAM test chip confirms that the canary cells track changes in temperature and V_DD and that they provide a reliable mechanism for protecting core cells in a closed loop V_DD scaling system. Power savings improve by up to 30times compared with the conventional guard-banding approach.