Ultra low power all-digital CMOS sensor read out circuit for optically powered biomedical systems

In this paper, an ultra low power all digital sensor read out circuit architecture which requires very low power is proposed. The proposed circuit is targeted for optically powered biomedical applications. The read-out circuit is utilized for the measurement of capacitive and resistive type of transducers. The measurement method is based on the fact that both capacitive and resistive sensors can be utilized to introduce delay in the signal transmission path. The proposed circuit architecture is composed of entirely digital components and it measures the introduced delay using only single input clock signal. The proposed architecture is implemented on UMC 180 nm CMOS technology and simulation results are presented. The proposed circuit operates with 1.2 V supply that is generated by the optical power harvesting and charge pump unit, while consuming 70.4 mW. The results confirm that the proposed circuit can be utilized in optically powered biomedical applications for carrying out capacitive and resistive sensor measurements.