Embeddable Circuit for Orientation Independent Processing in Ultra Low-Power Tri-axial Inertial Sensors

In this work, a new custom circuit is proposed to make the acquisitions of low-power tri-axial accelerometers independent from the spatial orientation of the sensors. For the purpose, a new vector rotation algorithm has been developed in order to reduce the overall computational effort and the complexity of the resulting circuit. The modularity of the computational scheme and the specific design choices have limited the area occupancy and the power dissipation of the circuit to negligible values with respect to the circuitry embedded in typical low-power accelerometers. The design has been prototyped with a Xilinx Artix-7 FPGA, where it achieves a maximum throughput of 81.2 kHz. Synthesis using a 65 nm CMOS standard cells library provides a maximum throughput of 223 kHz and an occupied area of 0.024 mm2. By setting the sample rate of the sensor to 25 Hz used as reference in many motion sensing applications, the standard cells power dissipation is about 1 W. Comparisons with the state-of-the-art in the literature show a maximum area and power reduction of 40% and 55%, respectively.