A single chip fluorometer for fluorescence lifetime spectroscopy in 65nm CMOS

This paper presents a low-power CMOS fluorometer that utilizes the frequency-domain fluorescence lifetime spectroscopy for oxygen sensing applications. The proposed fluorometer consists of a P+-buried/N-Well/P-Substrate photodiode for optical sensing, a novel phase readout circuit with integrated zero-crossing detection for extracting the frequency-domain phase-shift into a time-domain delay signal, and a high resolution Time-to-Digital Converter (TDC) for direct digital output generation. A prototype chip has been fabricated in a low-power 65nm CMOS technology and has been characterized via a sequence of oxygen sensing experiments, during which the fluorescence lifetime of a Ruthenium complex based oxygen sensor is measured as a function of the oxygen concentration. With only 370μW power consumption, the proposed fluorometer architecture and its unique phase readout scheme offer an attraction solution for developing low-power, low cost, and highly integrated devices for time-resolved fluorescence spectroscopy.