TDPRO: Time-Domain-Based Computing-in Memory Engine for Ultra-Low Power ECG Processor

For the wearable biomedical signal detection, both high accuracy and low-power consumption are critical requirements. Various works have employed the neural network to improve the detecting accuracy and develop the biomedical processor. However, the biomedical processor with neural network engine contains massive data movements and large data buffers. One solution is the computing-in memory (CIM) architecture, which locates more data near the computing engine to reduce data movements. In traditional CIM-based solution, the detecting accuracy and power consumption is difficult to be optimized simultaneously, where the accuracy should be satisfied for the detection. To date, the time-domain computing engine have been developed to employ both digital and time domain computation. In this work, we present a high-precision time-domain engine to perform 8-bit multiplication and addition operation for the biomedical signal detection. With the high precision time-domain engine, we develop a CIM-based neural-network processor, namely TDPRO, to perform the detection of arrhythmia. In addition, we develop TD-zero-jumping (TDJ) and idle-shutdown (ISD) techniques according to signal features and data mapping strategy, further optimizing the power consumption. Based on our evaluation, the TD-based 8-bit mulitply-accumulation operation is robust, without declining the accuracy of biomedical signal detection. We design a ECG processor with the proposed TDPRO architecture, which obtains 98.60% high accuracy and 75.7% power saving compared to the recent the state-of-the-art study.