13.8 A 32kb SRAM for error-free and error-tolerant applications with dynamic energy-quality management in 28nm CMOS

Voltage scaling is widely used to improve SRAM energy efficiency [1-2], particularly in mobile systems with tight power budgets. The resulting energy benefits are limited by the minimum voltage ensuring error-free operation, Vmin, which has stagnated due to growing process variation in advanced technology nodes [3]. Error-tolerant applications and systems (e.g., multimedia) allow more aggressive voltage scaling by operating below Vmin, which is acceptable if errors due to bitcell write/read failures do not perceptibly reduce application quality (e.g., image quality). Unfortunately, in traditional SRAMs bit error rate degrades rapidly for VDD <; Vmin [4], limiting energy gains. Under a given quality target, further energy reduction is possible through application-specific methods that exploit the features of data stored in a given application [4-5]. However, these approaches are not reusable across applications, and further the energy-quality trade-off is fixed at design time, which degrades energy savings in applications with lower quality targets and in chips near typical corner.