A Wireless FSCV Monitoring IC With Analog Background Subtraction and UWB Telemetry

A 30- $\mu {\rm W}$ wireless fast-scan cyclic voltammetry monitoring integrated circuit for ultra-wideband (UWB) transmission of dopamine release events in freely-behaving small animals is presented. On-chip integration of analog background subtraction and UWB telemetry yields a 32-fold increase in resolution versus standard Nyquist-rate conversion alone, near a four-fold decrease in the volume of uplink data versus single-bit, third-order, delta-sigma modulation, and more than a 20-fold reduction in transmit power versus narrowband transmission for low data rates. The 1.5- ${\rm mm}^{2}$ chip, which was fabricated in 65-nm CMOS technology, consists of a low-noise potentiostat frontend, a two-step analog-to-digital converter (ADC), and an impulse-radio UWB transmitter (TX). The duty-cycled frontend and ADC/UWB-TX blocks draw 4 $\mu {\rm A}$ and 15 $\mu {\rm A}$ from 3-V and 1.2-V supplies, respectively. The chip achieves an input-referred current noise of 92 ${\rm pA}_{\rm rms}$ and an input current range of $\pm {430}~{\rm nA}$ at a conversion rate of 10 kHz. The packaged device operates from a 3-V coin-cell battery, measures 4.7 $\,\times\,$ 1.9 ${\rm cm}^{2}$ , weighs 4.3 g (including the battery and antenna), and can be carried by small animals. The system was validated by wirelessly recording flow-injection of dopamine with concentrations in the range of 250 nM to 1 $\mu {\rm M}$ with a carbon-fiber microelectrode (CFM) using 300-V/s FSCV.