Current sensing in software for electronic fuse applications : Analysis of two different current measurement implementations

Abstract: Relays and fuses are used in a multitude of applications to deliver and control current to its consumers. To improve the controllability of both the fuse and relay function, they can be moved to software. This will not only increase the number of available features but can also give live feedback of the systems current state. For an electronic fuse to work the software needs to be able to measure the amount of current flowing through the circuit. For this a voltage drop can be measured across a series resistor. This can be implemented in several ways and will because of this utilize the resources of the controlling microcontroller differently. This thesis focuses on the software implementation of two current measuring circuits and will characterize the behavior of these in terms of making it simple to compare their advantages and disadvantages. Any hardware related aspect found to have an impact on the result will be taken into account as well. Two implementations, using two different integrated circuits, are tested against each other. MAX4172 is fully analog while the INA226 is half digital. A shorter study of current sensing in general is made but the foundation of the study is the datasheets and characteristics of the components chosen. In this thesis, both the hardware and the software is designed and built which end with gathering data in two different electronic fuse scenarios. The thesis concludes that the two implementations as electronic fuse is at least a factor of 10 faster than the traditional breaking fuse. It also concludes that both implementations have their advantages and either may be the right solution depending on the intended end application. The fully analog solution is generally faster but is more susceptible to external noise and bad hardware design whereas the half digital is slower but more forgiving and thus shows of more precise measurements out of the box.