Low-voltage fluxgate magnetic current sensor interface circuit with digital output for portable applications

In this paper we present a complete low-voltage, low-power and high linearity CMOS interface circuit for fluxgate magnetic sensors for current measurement applications. The integrated circuit provides the correct excitation signal to the fluxgate sensors and reads-out the sensor signals from the sensing coils. The proposed circuit allows us to deal with sensors featuring different values of the excitation coil resistance and to process the sensing coil signals with a power consumption lower than 1 mW. The interface circuit consists of three different modules, namely a timing block, an excitation block and a read-out chain. The interface circuit, has been implemented with two different excitation circuits, operating at 5 V and 3.3 V, respectively, without any high-voltage process options. The read-out chain performs a synchronous demodulation of the even harmonics, in order to extract the value of the external magnetic field. Furthermore, it is possible to switch-on a 13 bit ADC, to provide at the output the demodulated signal as a digital word.