Management system for MEMS inertial sensors

• US 8,220,329 B2
• Filed: 03/20/2009
• Issued: 07/17/2012
• Est. Priority Date: 03/21/2008
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Analog Devices, Inc.
• Inventors: Lee, James M.
• Primary Examiner(s): Caputo, Lisa
• Assistant Examiner(s): HERNANDEZ-PREWIT, ROGER
• Application Number:
  US12/408,536
• Publication Number:
  US 20090293615A1
• Time in Patent Office: 1,215 Days
• Field of Search: 735/140.1
• US Class Current: 73/514.01
• CPC Class Codes: G01P 1/127 for acceleration values
• CPC Class Codes: G01P 15/0891 with indication of predetermined acceleration values G01P15/135 takes precedence
• CPC Class Codes: G01P 15/18 in two or more dimensions
• CPC Class Codes: G11B 19/043 by detecting a free-fall condition

Abstract

A MEMS system includes an inertial sensor having sensor circuitry and management circuitry implemented with the sensor circuitry. The management circuitry includes a detection module that detects a condition of the system and a management module that coordinates the functionality of the inertial sensor and the detection module based on the detected condition.

Claims

1. A MEMS system that interacts with a microprocessor, the MEMS system comprising:

a MEMS inertial sensor configured to detect motion and produce data values related to the detected motion;

memory operatively coupled with the MEMS inertial sensor, the memory being configured to receive and store the data values from the MEMS inertial sensor;

a detection module operatively coupled with the MEMS inertial sensor and the memory, the detection module being configured to process the data values and to detect an inertial state of the MEMS inertial sensor based on the processed data values, the inertial state including an active state and an inactive state, the MEMS system configured to store the data values, the processed data values, or both in the memory in both the active state and the inactive state, the detection module being configured to detect an amount of data stored in the memory; and

a management module operatively coupled with the detection module and the memory, the management module being configured to receive the detected inertial state of the MEMS inertial sensor from the detection module, the management module being configured to signal the microprocessor to read the data values stored in the memory based on the inertial state and/or the amount of the data stored in the memory.

2. The system of claim 1, further comprising the microprocessor in communication with the management module and the memory.

3. The system of claim 1, wherein the memory stores the data values received by the inertial sensor in a first-in-first-out buffer type of configuration, a stream buffer type of configuration, or both.

4. The system of claim 1, wherein the inertial state further includes free fall detection, tap detection, double tap detection, and change in orientation detection.

5. The system of claim 4, wherein the memory stores the data values in a stream buffer type of configuration when in one inertial state, and the memory stores the data values in a first-in-first-out buffer type of configuration when in another inertial state.

6. The system of claim 1, wherein the detection module detects the active state by calculating a change in acceleration and comparing the change in acceleration to a threshold, wherein the change in acceleration is determined using an acceleration bias captured by the inertial sensor and a measured acceleration produced by the inertial sensor.

7. The system of claim 6, wherein the measured acceleration produced by the inertial sensor is measured at a sample rate, and the management module modifies the sample rate when the active state is detected.

8. The system of claim 1, wherein the detection module detects the inactive state by calculating a change in acceleration, comparing the change in acceleration to a threshold, determining if the change in acceleration is less than the threshold, and if the change in acceleration is less than the threshold, determining if a predetermined period of time has elapsed, wherein the change in acceleration is determined using an acceleration bias captured by the inertial sensor and a measured acceleration produced by the inertial sensor.

9. The system of claim 8, wherein the measured acceleration produced by the inertial sensor is measured at a sample rate, and the management module modifies the sample rate when the inactive state is detected.

10. The system of claim 1, wherein the inertial sensor is formed on a die and the management module is formed on or in the die.

11. The system of claim 1, wherein the management module is formed on or in a first die, and the MEMS inertial sensor is formed on or in a second die that is in communication with the first die.

12. The system of claim 1, wherein the inertial sensor is an accelerometer.

13. The system of claim 1, wherein the inertial sensor is a gyroscope.

14. A management system for a MEMS inertial sensor, the system comprising:

memory configured to receive and store data values from the MEMS inertial sensor;

a detection module operatively coupled with the memory, the detection module being configured to process the data values and to detect an inertial state of the MEMS inertial sensor based on the processed data values, the inertial state including an active state and an inactive state, the management system configured to store the data values, the processed data values, or both in the memory in both the active state and the inactive state, the detection module being configured to detect an amount of data stored in the memory; and

a management module operatively coupled with the detection module and the memory, the management module being configured to receive the detected inertial state of the MEMS inertial sensor from the detection module and to modify a configuration of the memory based on the detected inertial state.

15. The management system of claim 14, wherein the management module is further configured to signal a microprocessor to read the data values stored in the memory based on the inertial state and/or the amount of the data stored in the memory.

16. The management system of claim 14, wherein the configuration of the memory is a first-in-first-out buffer type of configuration, a stream buffer type of configuration, or both.

17. The management system of claim 14, wherein the inertial state further includes free fall detection, tap detection, double tap detection, and change in orientation detection.

18. The management system of claim 17, wherein the management module modifies the configuration of the memory to a stream buffer type of configuration when in one inertial state, and modifies the configuration of the memory to a first-in-first-out type of configuration when in another inertial state.

19. The management system of claim 14, wherein the MEMS inertial sensor is an accelerometer.

20. The management system of claim 14, wherein the MEMS inertial sensor is a gyroscope.