Quasi-digital front-ends for current measurement in integrated circuits with giant magnetoresistance technology

In this study, the authors report on two different electronic interfaces for low-power integrated circuits electric current monitoring through current-to-frequency (I-f) conversion schemes. This proposal displays the intrinsic advantages of the quasi-digital systems regarding direct interfacing and self-calibrating capabilities. In addition, as current-sensing devices, they have made use of the giant magnetoresistance (GMR) technology because of its high sensitivity and compatibility with standard complementary metal oxide semiconductor processes. Single elements and Wheatstone bridges based on spin-valves and magnetic tunnel junctions have been considered. In this sense, schematic-level simulations for integration in Austria Microsystems 0.35 mu m technology have been corroborated by means of experimental measurements with the help of printed circuit board prototypes and real GMR devices. Tables with relevant parameters (silicon area, power consumption, sensitivity etc.) have been constructed as practical tools for designers. Electric currents down to 2 mu A have been resolved in this way.