A 0.4 V 298 nJ/op Neural Signal Spectral Feature Extraction Module With Novel Approximate MACs and Custom Compressors

Ultra low-power and high energy-efficient digital FIR filters and magnitude summation circuit are the key modules in spectral feature extraction (SFE) of portable thin-battery neural signal processing chips. A tailored SFE module design is presented in this brief. By adopting custom appropriate multiply-accumulate (MAC) circuits and novel ratioed logic style in custom standard cells’ design, the proposed SFE design is simplified with shorter logical path and faster subthreshold logic complex gates. Accuracy analysis is carried out to optimize the circuit structure with acceptable calculated results. Fabricated in 90 nm CMOS technology, the design has achieved 30% reduction of silicon area and 0.2 V lower supply voltage (hence over 50% elimination of power dissipation) in measurement, while compared to other regular works by standard design method. And the accuracy lost is within tolerant range.