Ultra low power processor operates at near threshold voltage

The processor is designed to deliver clock speeds up to 1MHz at voltages down to 0.4V. In tests based on a Fast Fourier Transform use case, it was said to consume just 79µW. The device has been customised for biomedical applications such as ECG and EEG monitoring, and was realised by creating an interface architecture around a general purpose processor core. One of the key developments, according to the researchers, was the ability to reduce the operating voltage while delivering enough performance to meet application needs, and maintaining that performance over a range of operating voltages and temperatures. This was achieved by forward biasing the transistors within the processor, allowing it to operate at voltages just above the threshold for the cmos process used. The researchers say the operating voltage can be adjusted between the processor's nominal voltage of 1.1V and a minimum voltage of 0.4V depending on the current performance requirements. To ensure reliability, the team connected canary flip-flops to the most timing critical parts of the processor. These are designed to fail before the processor's circuits do and can be monitored – allowing the operating voltage to be scaled up before noise affects the processor. To reduce energy consumption even further, the researchers enabled the interface to control the state of individual components on the chip separately, for example turning off the processor core or reducing the voltage in the memory when these components were not required.