0.08mm2 128nW MFCC Engine for Ultra-low Power, Always-on Smart Sensing Applications

Mel frequency cepstral coefficient (MFCC) features are widely used in applications such as keyword spotting, bearing fault detection and heart sound classification. This work proposes a low power MFCC engine that enables its use for battery-powered edge applications. Three hardware algorithm co-optimizations were adopted to achieve energy efficient MFCC hardware implementation. The approximated MFCC features due to the optimizations still allows good accuracy when deployed in several applications such as keyword spotting and bearing fault detection, reporting negligible accuracy drop of $\le 1.5$%. The proposed MFCC hardware consumes only 128nW at 0.3V supply and occupies only 0.08mm
²
in 40nm CMOS technology, which are $5 \times $ and $2.75 \times $ power and area reduction respectively when compared to the prior arts.