A 20µW neural recording tag with supply-current-modulated AFE in 0.13µm CMOS

Perpetual measurement of brain activity in untethered small animal in-vivo experiments requires low power micro-systems incorporating amplification, A/D conversion, and short range wireless transmission. Overall power and communication strategies depend largely on size constraints of the implant site. For extremely small implants, these systems generally call for permanently powering the implanted recording system without the use of a battery. Such systems are primarily based on low frequency and close proximity inductive links for power and communication [1]. Alternatively, in scenarios where the implant site is less constrained, the use of small batteries can provide increased communication range [2]. In this paper, we present a 20µW neural recording tag architecture that can be either remotely powered using a transponder-reader link or operated from a small battery for increased communication range. The key features that enable this increased system flexibility are the use of a supply current modulation strategy, minimizing average power consumption of the analog-front end (AFE) and allocating larger instantaneous power levels for amplification, processing, and communication, and an uplink communication scheme based on far-field backscattering or near-field load modulation with compatibility for both battery and remotely powered systems.