A 77.8-dB DR, 114.2 fJ/Step Amplifier-Less Current-to-Digital Converter

A charge-recycled amplifier-less current-to-digital converter (CDC) is presented in this paper. The highly digital CDC is based on ultra-low-power subthreshold operation, amplifier-free design, scalable current range, and high-resolution digital circuits. It is realized using a mixed-signal approach by utilizing an analog comparator, 6-bits current steering DAC, an implicit passive integrator, and digital signal conditioning circuits. The proposed converter can be operated in tri-modes to support multiple current sensing applications, i.e. Mode1: current range (CR) from 10nA to 400nA, Mode 2: CR from 0.5μA to 5μA, and Mode3: CR from 2.5μA to 42.5μA. The proposed CDC is implemented in 180nm CMOS process with an active area of 0.54 mm
²
while consuming 11.2μW. It achieves a 77.8dB dynamic range at a bandwidth of 300Hz from 1V supply with an FoM of 114.2fJ/step.