Sensors find a variety of applications in portable electronics, automotive and biomedical solutions. The demand for low power and high dynamic range makes the design of digital sensor readout circuits quite challenging. Traditionally, these circuits are realized using amplifiers with passive feedback or precision analog comparators which are power hungry and not amenable to technology scaling.
This thesis presents design techniques for a low power, amplifier-free, digital sensor current readout circuit. It is realized using an implicit passive integrator, VCO-based quantizer, and mostly digital circuits. A digital IIR filter is used to increase the loop gain and bias the sensor accurately across a wide range of values. Fabricated in a 0.18μm CMOS process, the prototype readout circuit achieves 900pA accuracy over an input current range of 4μA, consumes a total of 77.8μA current, and occupies an active area of 0.36mm² .