A VCO-based current-to-digital converter for sensor applications

摘要

A current sensing VCO based ADC architecture is realized using a passive integrator, VCO-based quantizer, and mostly digital circuits. A digital IIR filter is used instead of an analog loop filter to tackle VCO non-linearity in a power efficient and scaling friendly manner. The prototype circuit designed for an ambient light sensor application achieves 900pA accuracy over an input current range of 4μA, consumes a total of 77.8μA current, and occupies an active area of 0.36mm in 0.18μm CMOS process.