A 1MHz 256kb Ultra Low Power Memory Macro for Biomedical Recording Applications in 22nm FD-SOI Using FECC to Enable Data Retention Down to 170mV Supply Voltage

In biomedical sensor platforms, low energy consumption is of utmost importance to extend battery life. A dominant contributor in the energy budget of such platforms is the always-on recording memory. Hence, a low energy memory is required. This paper implements such a memory with aggressive voltage scaling to run the memory in the sub-threshold region during retention. Fine grained forward error correction is a key enabler for this. It allows operation of the memory beyond the point of first failure and acts similar to EDAC techniques for timing failure detection in voltage-scaled microcontrollers. The memory is embedded in a RISC-V microcontroller and fabricated in a 22nm FDSOI technology. Measurements show an always-on retention voltage down to 170mV, which results in a total average power of only 5.11uW, a 70% reduction compared to the signoff point. The memory is extensively tested with memtest and found to be fully functional up to 1.2 MHz.