Abstract
A multi-function microelectromechanical system (MEMS) with a three-axis magnetometer (MAG) and three-axis accelerometer (ACC) function was implemented with an application-specific integrated circuit (ASIC)-compatible complementary metal-oxide-semiconductor (CMOS) 0.18 μm process. The readout circuit used the nested chopper, correlated double-sampling (CDS), noise reduction method; the frequency division multiplexing method; the time-division multiplexing method; and the calibration method. Sensing was performed by exciting the MEMS three-axis magnetometer at X/Y/Z axes mechanical resonant frequencies of 3.77/7.05/7.47 kHz, respectively. A modest die-level vacuum packaging resulted in in-plane and out-of-plane mechanical quality factors of 471–500 and 971–1000, respectively. The sensitivities of both the three-axis magnetometer with 2 mA driving current and the three-axis accelerometer were 7.1–10.7 uV/uT and 58.37–88.87 uV/ug. The resolutions of both the three-axis magnetometer with 2 mA driving current and three-axis accelerometer resolution were 44.06–87.46 nT/√Hz and 5.043–7.5 ng/√Hz. The resolution was limited by circuit noise equivalent acceleration (CNEM) and Brownian noise equivalent magnetic field (BNEM).
Highlights
To further reduce hardware cost, this paper proposes that a three-axis magnetometer and a three-axis accelerometer (ACC) share one microelectromechanical system (MEMS) structure
We studied microelectromechanical systems (MEMS) with multi-functions including a three-axis MAG, a three-axis ACC, and backend circuitry
Two solutions for curvature have been presented: The first solution is that the readout circuit uses noise reduction technology, the frequency division multiplexing method, and the time-division multiplexing method
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The magnetic sensor measures change in the three-axis geomagnetism with a mobile device and simulate the angular movement of the gyroscope through algorithms. Are done well, and the MEMS gyroscope can be replaced by a three-axis MAG. To further reduce hardware cost, this paper proposes that a three-axis magnetometer and a three-axis accelerometer (ACC) share one microelectromechanical system (MEMS) structure. A single-structure three-axis Lorentz force MAG had a 30 nT/ HZ resolution in Reference [2]. The ACC readout circuit used a low-frequency noise reduction technique in Reference [3]. Development of a multi-axis complementary metal-oxidesemiconductor (CMOS)–MEMS resonant magnetic sensor Lorentz and electromagnetic forces were presented in Reference [4]. Z-axis MAGs for MEMS inertial measurement units using an industrial process are presented in Reference [5]. An area-efficient three-axis MEMS Lorentz force MAG was the smallest Lorentz force sensor [7]
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