Short word length NULL convention logic FIR filter for low power applications

This paper presents an asynchronous single bit Delta Sigma FIR-like filter designed using NULL Convention Logic (NCL) that can be operated near the threshold region of its transistor components aimed at low power, low bandwidth applications such as ECG signal acquisition. The proposed design is compared against an equivalent synchronous single bit filter designed using conventional Boolean logic in terms of power, performance and area. The circuit exhibits correct operation even within the variability-prone near/sub-threshold region. As a result it is able to operate with greatly reduced supply voltages to achieve a low value of power-delay product. The example implementation using 130nm technology achieves a power reduction of 5X, compared to a traditional synchronous filter design with similar performance targets.