Free fall detector device and free fall detection method

• US 7,802,476 B2
• Filed: 01/19/2007
• Issued: 09/28/2010
• Est. Priority Date: 01/20/2006
• Status: Active Grant

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Lasalandra, Ernesto, Ungaretti, Tommaso
• Primary Examiner(s): Chapman; John E
• Application Number:
  US11/625,124
• Publication Number:
  US 20070188969A1
• Time in Patent Office: 1,348 Days
• Field of Search: 735/10, 735/141.8, 735/143.2, 702/141, 360/75, 324/661
• US Class Current: 73/514.32
• CPC Class Codes: G01P 15/0891 with indication of predetermined acceleration values G01P15/135 takes precedence
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 15/131 with electrostatic counterbalancing means
• CPC Class Codes: G01P 15/18 in two or more dimensions
• CPC Class Codes: G11B 19/043 by detecting a free-fall condition
• CPC Class Codes: G11B 21/12 Raising and lowering; Back-spacing or forward-spacing along track; Returning to starting position otherwise than during transducing operation

Abstract

A free-fall detector device includes an inertial sensor, a detection circuit associated to the inertial sensor, and a signal source for supplying a read signal to the inertial sensor. The device moreover includes: a storage element, selectively connectable to the detection circuit for storing a feedback signal generated by the detection circuit in response to the read signal supplied to the inertial sensor; and a feedback circuit coupled to the storage element for supplying the feedback signal to the inertial sensor so that the detection circuit generates at least one detection signal in response to the feedback signal supplied to the inertial sensor.

Claims

1. A free-fall detector device, comprising:

an inertial sensor;

an integrated charge circuit coupled to said inertial sensor;

a signal source, configured to supply a read signal to said inertial sensor;

a storage element, selectively connectable to an output of said integrated charge circuit and configured to store a feedback signal generated by said integrated charge circuit in response to said read signal supplied to said inertial sensor; and

a feedback circuit coupled to said storage element and configured to supply said feedback signal to said inertial sensor, said integrated charge circuit configured to generate at least one detection signal in response to said feedback signal supplied to said inertial sensor.

2. The device according to claim 1, wherein said inertial sensor comprises first, second, and third detection elements responding to loads oriented, respectively, according to first, second, and third independent detection axes, and said integrated charge circuit is selectively connectable to said first, second, and third detection elements for generating first, second, and third detection signal, respectively correlated to loads oriented, respectively, according to the first, second, and third detection axes.

3. The device according to claim 2, comprising an adder circuit for adding said first, second, and third detection signal.

4. The device according to claim 3, comprising a comparator, associated to said adder circuit for comparing an addition signal, generated by said adder circuit, with a reference signal.

5. The device according to claim 1, comprising at least one hold selective-connection element and at least one feedback selective-connection element controlled so as to connect said storage element to said integrated charge circuit in a first operating configuration and to said inertial sensor in a second operating configuration.

6. The device according to claim 1, wherein said storage element comprises at least one capacitor.

7. The device according to claim 1, wherein said integrated charge circuit comprises a charge-voltage converter.

8. The device according to claim 7, wherein said charge-voltage converter comprises a charge integrator.

9. The device according to claim 8, wherein said charge integrator is a selectively connectable capacitive feedback charge integrator.

10. The device according to claim 8, wherein said charge integrator is fully differential.

11. The device according to claim 1, wherein said read signal comprises a step voltage.

12. A free-fall detection method, comprising:

supplying a read signal to an inertial sensor;

storing a differentially integrated feedback signal, generated by said inertial sensor in cooperation with an integrated charge circuit in response to said read signal;

supplying said feedback signal to said inertial sensor; and

generating at least one detection signal by said inertial sensor in cooperation with the integrated charge circuit in response to said feedback signal.

13. The method according to claim 12, comprising generating first, second, and third detection signals, respectively correlated to loads, oriented, respectively, according to first, second, and third detection axes.

14. The method according to claim 13, comprising adding said first, second, and third detection signals together.

15. The method according to claim 14, comprising comparing a sum of said first, second, and third detection signals with a reference value.

16. The method according to claim 12, wherein said step of storing comprises coupling a storage element to at least one output of said inertial sensor.

17. The method according to claim 16, wherein said step of supplying said feedback signal comprises coupling said storage element to at least one drive terminal of said inertial sensor.

18. The method according to claim 12, wherein said read signal comprises a step voltage.

19. The method according to claim 12, further comprising converting the feedback signal generated by the inertial sensor from a charge to a voltage signal prior to storing the feedback signal.

20. The method according to claim 12, wherein said storing includes storing the feedback signal in a storage element during a first phase during which the storage element is disconnected from an input of the inertial sensor and the step of supplying the feedback signal includes supplying the feedback signal during a second phase during which the storage element is disconnected from an output of the inertial sensor.

21. A portable electronic device, comprising:

a control unit structured to control the portable electronic device; and

a free-fall detector device coupled to the control unit and including;

an inertial sensor;

an integrated charge circuit associated to said inertial sensor;

a signal source, configured to supply a read signal to said inertial sensor;

a storage element, selectively connectable to an output of said integrated charge circuit and configured to store a feedback signal generated by said integrated charge circuit in response to said read signal supplied to said inertial sensor; and

a feedback circuit coupled to said storage element and configured to supply said feedback signal to said inertial sensor, so that said integrated charge circuit generates at least one detection signal in response to said feedback signal supplied to said inertial sensor.

22. The portable electronic device according to claim 21, wherein said inertial sensor comprises first, second, and third detection elements responding to loads oriented, respectively, according to first, second, and third independent detection axes, and said integrated charge circuit is selectively connectable to said first, second, and third detection elements for generating first, second, and third detection signal, respectively correlated to loads oriented, respectively, according to the first, second, and third detection axes.

23. The portable electronic device according to claim 22, wherein the free-fall detector device includes an adder circuit for adding said first, second, and third detection signal.

24. The portable electronic device according to claim 23, wherein the free-fall detector device includes a comparator, associated to said adder circuit for comparing an addition signal, generated by said adder circuit, with a reference signal.

25. The portable electronic device according to claim 21, wherein the free-fall detector device includes at least one hold selective-connection element and at least one feedback selective-connection element controlled so as to connect said storage element to said integrated charge circuit in a first operating configuration and to said inertial sensor in a second operating configuration.

26. The portable electronic device according to claim 21, wherein said storage element comprises at least one capacitor.

27. The portable electronic device according to claim 21, wherein said integrated charge circuit comprises a charge-voltage converter.

28. The portable electronic device according to claim 21, wherein said read signal comprises a step voltage.

29. The portable electronic device according to claim 21, further comprising an operative element sensitive to free-falling, wherein the control unit is structured to suspend operation of the operative element in response to receiving, from the free-fall detector device, a free-fall signal indicating that the device is free-falling.