A Compact Low-Power Bidirectional Two-Wire Interface for Digital Neural Probes

Interfacing high-density neural probes, that integrate all the circuitry needed to digitize brain activity in situ, requires a thin and conformal cable. Such wiring must be constrained in size to minimize tissue damage during insertion or due to micro motions when operated in a chronic setting. Reducing the number of traces required to connect these devices leads to thinner and more flexible cables or allows to enhance the data rate by allocating wider traces. A lower number of contacts is also less prone to reliability issues in long-term applications. In this paper, a two-wire bidirectional interface for neural probes is presented that minimizes data overhead for configuration and readout. Moreover, the implemented handshaking protocol is designed to adapt to varying line delays that may occur due to different cable lengths or time-varying environmental effects. The interface has been validated in a prototype ASIC fabricated with a 180 nm CMOS technology and a supply voltage of 1.2 V.