Hybrid Hall microsystem for high dynamic range/large bandwidth magnetometry applications

We have developed a hybrid magnetometer combining a high performance III-V semiconductor based Hall sensor with a purposely developed specific IC using a mixed-mode 0.35 mum CMOS process. The ASIC fulfills several functions: analog signal processing (4-phase spinning current modulation) providing an efficient low-frequency noise reduction, reference voltage generation, Sigma-Delta based AD conversion and demodulation, digital filter blocks and serial output management. The signal bandwidth can be set between 1 and 1500 Hz. The equivalent input noise is practically flat (i.e. free from 1/f noise) in the 0.1 Hz-1.5 kHz frequency range, and amounts to 100-150 nT/radicHz. A large dynamic has been demonstrated, the total error being less than 0.2% of the measured value in 3.5 decades of signal amplitude. This study exemplifies the interest of hybrid technology for sensing in general, featuring integrated functionalities in standard low cost CMOS IC with high performance non silicon sensors.