A current controlled oscillator based readout front-end for neurochemical sensing in 65nm CMOS technology

This paper presents the design of an integrated current-controlled oscillator (CCO) based readout front-end for neurochemical sensing applications. The readout front-end chip is implemented in 65 nm CMOS technology and occupies an area of 0.059 mm2. The proposed design supports an input current range of 1.2 μA (±600 nA) and can also be configured to support wider current range. The CCO-based structure utilized in this design results in noise averaging of the detected neurochemical input signal due to its inherent ΔΣfirst-order noise shaping and anti-alias filtering characteristics. Thus, the prototype chip achieves a current resolution of 100 pA and can detect dopamine concentrations as small as 10 μMol based on measured data from novel diamond-like carbon electrodes. In addition, the digital codes obtained from the readout front-end attain a signal-to-noise (SNR) of 82 dB and linearity limited effective-number-of-bits (ENOB) of 8 at full current range input, without employing any calibration or linearization techniques. The proposed read-out front-end consumes 33.7 μW of power in continuous operation.