A neuromimetic ultra low-power ADC for bio-sensing applications

A compact 8-bit analog-to-digital converter (ADC) targeted for bio-sensing applications in systems-on-chip is presented. In particular, the design and implementation of the ADC with operation similar to a natural neuron cell in that it produces actions potentials corresponding to a stimulus of sufficient strength is described. An energy-saving buffer by reducing its effective capacitance is proposed to achieve low power consumption, and a specially designed switch and calibration system were incorporated in the design to improve the integral non-linearity (INL) of the ADC. The circuit was implemented in a standard 0.18µm CMOS process technology with a 1.5V supply, and a compact core area of 0.05 mm2. Post layout simulations reveal that for a full scale range input current of 16 µA, the ADC maintains a maximum differential non-linearity (DNL) and INL of less than 0.16 LSB and 0.41 LSB respectively. The ADC achieves an ultra low energy dissipation of 5.46 pJ/cycle when operated at a sampling rate of 500 kS/s. This energy consumption is one of the lowest ever reported to date.