Magnetic inertial sensor and method for operating the same

Patent metadata

Field	Value
Publication number	US-9322839-B2
Application number	US-201313854782-A
Country	US
Kind code	B2
Filing date	Apr 1, 2013
Priority date	Apr 2, 2012
Publication date	Apr 26, 2016
Grant date	Apr 26, 2016

Abstract

An inertial sensor having a body with an excitation coil and a first sensing coil extending along a first axis. A suspended mass includes a magnetic-field concentrator, in a position corresponding to the excitation coil, and configured for displacing by inertia in a plane along the first axis. A supply and sensing circuit is electrically coupled to the excitation coil and to the first sensing coil, and is configured for generating a time-variable flow of electric current that flows in the excitation coil so as to generate a magnetic field that interacts with the magnetic-field concentrator to induce a voltage/current in the sensing coil. The integrated circuit is configured for measuring a value of the voltage/current induced in the first sensing coil so as to detect a quantity associated to the displacement of the suspended mass along the first axis.

First claim

The invention claimed is:

1. An inertial sensor, comprising:
a body of semiconductor material, having a first surface and a second surface, the body including:
an excitation coil;
a first sensing coil extending at a first distance from the excitation coil along a first axis;

a suspended mass including a magnetic-field concentrator, the suspended mass extending above the first surface and being magnetically coupled to the excitation coil and to the first sensing coil, and configured to be displaced by way of inertia; and
a supply and sensing circuit electrically coupled to the excitation coil and to the first sensing coil, and configured to generate a time-variable flow of electric current through the excitation coil to generate a magnetic field that, in use, interacts with said magnetic-field concentrator to induce an electrical quantity in the first sensing coil, the supply and sensing circuit being configured to measure a value of said electrical quantity induced in the first sensing coil to detect a quantity associated with a displacement of the suspended mass, the supply and sensing circuit is further configured to:
acquire an effective frequency of variation in time of the flow of electric current and an effective wavelength associated with said effective frequency;
measure an apparent frequency of variation in time of said electrical quantity induced in the first sensing coil and obtaining an apparent wavelength associated to said apparent frequency;
compute, on the basis of the values of the effective wavelength and of the apparent wavelength, a value of velocity at which the suspended mass moves; and
determine a time derivative of the value of velocity to obtain a value of acceleration of the suspended mass.

2. The inertial sensor according to claim 1 wherein the electrical quantity induced in the sensing coil is a voltage or an electric current, and said value to be measured is a peak value or a root-mean-square value of the electrical quantity.

3. The inertial sensor according to claim 1 wherein the variation of the electrical quantity induced in the first sensing coil is due to a variation of reluctance of the magnetic circuit between the excitation coil and the first sensing coil, said magnetic circuit including the suspended mass provided with the magnetic-field concentrator.

4. The inertial sensor according to claim 1 wherein the quantity associated to the displacement of the suspended mass includes at least one of a direction and a sense of displacement of the suspended mass, a velocity of displacement of the suspended mass, and an acceleration of the suspended mass.

5. The inertial sensor according to claim 1 wherein the suspended mass is configured to be displaced along a first plane parallel to the first axis.

6. The inertial sensor according to claim 1 wherein the suspended mass is configured to be displaced in a second plane transverse to the first axis.

7. The inertial sensor according to claim 1 wherein the amount of the displacement of the suspended mass is measured according to the intensity of the magnetic field supplied by the magnetic-field concentrator to the first sensing coil.

8. The inertial sensor according to claim 1 wherein the flow of electric current is a time-variable signal with a frequency of from 1 Hz to 300 GHz.

9. The inertial sensor according to claim 1 wherein the magnetic-field concentrator is a layer of magnetic material.

10. The inertial sensor according to claim 1 wherein the excitation coil and the first sensing coil are planar windings extending parallel to the first surface of the body.

11. The inertial sensor according to claim 1 wherein said supply and sensing circuit includes: a current generator configured to generate the flow of electric current; and a current-sensing circuit, configured to detect a value associated with the current induced in the first sensing coil.

12. The inertial sensor according to claim 1 wherein the suspended mass includes a structural portion that includes the magnetic-field concentrator, said suspended mass being supported by one or more springs adapted to enable a movement of the suspended mass in a direction transverse to the first axis.

13. The inertial sensor according to claim 12 wherein the suspended mass is housed in a package having perimetral walls configured to surround the suspended mass at least partially, said one or more springs extending between the perimetral walls and the suspended mass, fixed with respect to the perimetral walls and to the structural portion of the suspended mass.

14. The inertial sensor according to claim 1 wherein the body includes a second sensing coil extending at a second distance from the excitation coil along a second axis coplanar and transverse to the first axis, the suspended mass being further configured to move along the second axis, the supply and sensing circuit being electrically coupled to the second sensing coil, and configured to measure, in use, a value of an electrical quantity induced in the second sensing coil to detect a quantity associated with a displacement of the suspended mass along the second axis.

15. The inertial sensor according to claim 14 wherein the amount of the displacement of the suspended mass along the second axis is measured according to the intensity of the magnetic field supplied by the magnetic-field concentrator to the second sensing coil.

16. The inertial sensor according to claim 14 wherein the body includes a third sensing coil, coplanar to, and extending at a third distance from, the excitation coil along the first axis, on the opposite side of the first sensing coil with respect to the excitation coil, the supply and sensing circuit being electrically coupled to the third sensing coil, and configured to measure, in use, a value of an electrical quantity induced in the third sensing coil to detect a quantity associated with the displacement of the suspended mass along the first axis with respect to the first and third sensing coils.

17. A portable system, comprising:
a processor;
an inertial sensor coupled to the processor, the inertial sensor including:
a body of semiconductor material having a first surface and a second surface, the body including:
an excitation coil;
a first sensing coil extending at a first distance from the excitation coil along a first axis;

a suspended mass including a magnetic-field concentrator, the suspended mass extending above the first surface and being magnetically coupled to the excitation coil and to the first sensing coil, and configured to displace by way of inertia; and

a supply and sensing circuit, electrically coupled to the excitation coil and to the first sensing coil, and configured to generate a time-variable flow of electric current through the excitation coil to generate a magnetic field that, in use, interacts with said magnetic-field concentrator to induce an electrical quantity in the first sensing coil, the supply and sensing circuit being configured to measure a value of said electrical quantity induced in the first sensing coil to detect a quantity associated to the displacement of the suspended mass, the supply and sensing circuit is further configured to:
acquire an effective frequency of variation in time of the flow of electric current and an effective wavelength associated with said effective frequency;
measure an apparent frequency of variation in time of said electrical quantity induced in the first sensing coil and obtaining an apparent wavelength associated to said apparent frequency;
compute, on the basis of the values of the eff

Assignees

• St Microelectronics Srl

Inventors

• Ricotti Giulio
• Pagani Alberto
• Fontana Fulvio Vittorio
• Mastromatteo Ubaldo

Classifications

• H10W90/754

  between a chip and a stacked insulating package substrate, interposer or RDL · CPC title

• H10W90/724

  between a chip and a stacked insulating package substrate, interposer or RDL · CPC title

• G01P15/11 Primary

  by inductive pick-up · CPC title

• G01P15/105 Primary

  by magnetically sensitive devices · CPC title

• B81B2201/025

  Inertial sensors not provided for in B81B2201/0235 - B81B2201/0242 · CPC title