Self-test architecture for mems accelerometer: humidity-proof, fully differential design and full mass control

Abstract

An accelerometer includes first and second stator-electrodes associated with a first-rotor, third and fourth stator-electrodes associated with a second-rotor, a first capacitance formed between the first-rotor and first stator-electrode, a second capacitance formed between the first-rotor and second stator-electrode, a third capacitance formed between the second-rotor and third stator-electrode, and a fourth capacitance formed between the second-rotor and fourth stator-electrode. A drive-circuit generates first and second periodic anti-phase stator drive-signals, and third and fourth periodic anti-phase stator drive-signals. To self-test, the drive-circuit applies the first, second, third, and fourth stator drive-signals to the first, second, third, and fourth stator-electrodes, and drives the first and second stator drive-signals with different voltage-swings but drives the third and fourth stator drive-signals with a same voltage-swing. A capacitance-to-voltage converter has a first-input coupled to the first and second capacitances, and a second-input coupled to the third and fourth capacitances.