A charge-based ultra-low power continuous-time ADC for data driven neural spike processing
The paper presents a novel topology of a continuous-time analogue-to-digital converter (CT-ADC) featuring ultra-low static power consumption, activity-dependent dynamic consumption, and a compact footprint. This is achieved by utilising a novel charge-packet based threshold generation method, that alleviates the requirement for a conventional feedback DAC. The circuit has a static power consumption of 3.75 μW, with dynamic energy of 1.39pJ/conversion level. This type of converter is thus particularly well-suited for biosignals that are generally sparse in nature. The circuit has been optimised for neural spike recording by capturing a 3 kHz bandwidth with 8-bit resolution. For a typical extracellular neural recording the average power consumption is in the order of ∼4 μW. The circuit has been implemented in a commercially available 0.35 μm CMOS technology with core occupying a footprint of 0.12 mm2.