The Necessity of Comparators in Wake-Up Receiver Circuits

Wake-up receivers (WuRxs) playa crucial role in enabling wireless sensor nodes to operate efficiently on battery power while ensuring low-latency communication. Typically, comparators are employed to facilitate the conversion from analog to digital signals. However, some recent proposals opt to exclude the comparator to achieve minimal power consumption. This article delves into the investigation of the shoot-through effect present in CMOS devices. Our measurements reveal that connecting analog signals directly to CMOS devices can lead to a significant increase in power consumption, reaching up to a thousandfold. Analyzing our findings in the context of existing research, we project that the shoot-through effect severely limits the battery life of sensor nodes in real-world applications. To address this challenge, we propose the use of nano-power comparators that do not exhibit shoot-through effects. While our proposed comparator circuit adds additional 175 nA of power consumption, it significantly enhances the reliability of various wake-up receivers.