Low power low noise integrated circuit for sensing and driving AMR-based three axis magnetometers

The relentless miniaturization of microelectronic technologies is leading to drastically reduce power consumption thus making possible the design of sensor nodes for distributed sensing or the integration of multiple sensing systems in portable, consumer electronic devices. In these systems, low-power low-noise front-ends have to acquire, digitize and transmit information. To improve energy efficiency design solutions should be found to keep power consumption as low as possible and improving the efficiency of all the circuit blocks. To meet the recent trends of consumer and in general portable electronic applications, an earth magnetic field sensing system to support the development of indoor navigation systems is presented in this work. The 3-axis AMR magnetic field sensing readout integrated circuit was designed in CMOS 0.35µm to provide the signal amplification, digitalization and offset correction. The AMR sensing system is designed to achieve 3mGa resolution, a full scale range of 20Ga drawing only 170µW per-axis from a 1.8V power supply and it is currently under measurements. In order to correct offsets by means of Set/Reset procedure, a logical block is designed and presented. To reduce the complexity and simplifying the measurements, the final measured data will be serialized and sent to the Labview software interface in order to processing the data. Moreover, to provide enough current to drive Set/Reset coils of AMR Sensor, an analog circuit is designed which is currently under measurement.