Temperature-adaptive dynamic voltage scaling for high temperature energy efficiency in subthreshold memory banks

Static random access memory (SRAM) circuits optimized for minimum energy consumption typically operate in the subthreshold regime with ultra-low power-supply-voltages. Both the read and the write propagation delays of a subthreshold memory circuit are significantly reduced with an increase in the die temperature. The excessive timing slack observed in the clock period of constant-frequency subthreshold memory circuits at elevated temperatures provides new opportunities to lower the active mode energy consumption. Temperature-adaptive dynamic supply voltage tuning technique is proposed in this paper to reduce the high temperature energy consumption of ultra-low-voltage subthreshold SRAM arrays. Results with a 64-bit times 64-bit memory array in the TSMC 180 nm CMOS technology indicate that the energy consumption can be lowered by up to 32.8% by dynamically scaling the supply voltage at elevated temperatures.