SYSTEM FOR DRIVING AN ARRAY OF MEMS STRUCTURES AND CORRESPONDING DRIVING METHOD

• US 20150344295A1
• Filed: 03/31/2015
• Published: 12/03/2015
• Est. Priority Date: 05/27/2014
• Status: Active Grant

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: GUANZIROLI, Federico, CONFALONIERI, Pierangelo, CATTANI, Alberto, GASPARINI, Alessandro
• Granted Patent: US 9,604,842 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: B81B 2201/0257 Microphones or microspeakers
• CPC Class Codes: B81B 2207/03 Electronic circuits for micromechanical devices which are not application specific, e.g. for controlling, power supplying, testing, protecting
• CPC Class Codes: B81B 2207/053 of movable structures
• CPC Class Codes: B81B 3/00 Devices comprising flexible or deformable elements, e.g. comprising elastic tongues or membranes B81B5/00 takes precedence
• CPC Class Codes: B81B 7/008 MEMS characterised by an electronic circuit specially adapted for controlling or driving the same B81B7/0087 takes precedence; arrangements for starting, regulating, braking, or otherwise controlling an actuator H02N; control arrangements or circuits for visual indicators G09G3/00
• CPC Class Codes: B81B 7/04 Networks or arrays of similar microstructural devices
• CPC Class Codes: H04R 19/005 using semiconductor materials
• CPC Class Codes: H04R 2201/003 Mems transducers or their use of the electrostatic type H04R19/005
• CPC Class Codes: H04R 3/007 Protection circuits for transducers
• CPC Class Codes: H04R 3/12 for distributing signals to two or more loudspeakers specially adapted for hearing aids H04R25/407
• CPC Class Codes: H05K 999/99 dummy group

Abstract

A system for driving a MEMS array having a number of MEMS structures, each defining at least one row terminal and one column terminal, envisages: a number of row driving stages, each for supplying row-biasing signals to the row terminal of each MEMS structure associated to a respective row; a number of column driving stages, each for supplying column-biasing signals to the column terminal of each MEMS structure associated to a respective column; and a control unit, for supplying row-address signals to the row driving stages for generation of the row-biasing signals and for supplying column-address signals to the column driving stages for generation of the column-biasing signals. The control unit further supplies row-deactivation and/or column-deactivation signals to one or more of the row and column driving stages, for causing deactivation of one or more rows and/or columns of the MEMS array.

Claims

1. A system to drive a MEMS array, the system comprising:

a plurality of row driving stages coupled to the MEMS array, the MEMS array having a plurality of MEMS structures that each have a row terminal and a column terminal, each of the plurality of row driving stages being configured to supply row-biasing signals to the row terminal of each MEMS structure associated with a respective row;

a plurality of column driving stages coupled to the MEMS array, each of the plurality of column driving stages being configured to supply column-biasing signals to the column terminal of each MEMS structure associated with a respective column; and

a control unit configured to supply row-address signals to said row driving stages to generate the row-biasing signals and to supply column-address signals to said column driving stages to generate the column-biasing signals,

the control unit being configured to further supply row-deactivation and column-deactivation signals to one or more of said row and column driving stages to cause deactivation of one or more rows and columns of said MEMS array.

2. The system according to claim 1, comprising a plurality of failure-detection stages coupled to the MEMS array and configured to detect at least one failure associated with one or more of said MEMS structures;

and said control unit is coupled to said failure-detection stages and is configured to identify a position of the failure at the one or more of said MEMS structures and to cause deactivation of the one or more rows and columns of said MEMS array that correspond to said position, the control use being configured to enable the respective row-deactivation and column-deactivation signals associated with the position of the failure.

3. The system according to claim 1 wherein said MEMS array comprises one or more redundancy rows and columns;

and said control unit is configured to activate one or more of said redundancy rows and columns upon deactivation of the one or more rows and columns of said MEMS array.

4. The system according to claim 1 wherein said row and column driving stages are configured, upon reception of the respective row-deactivation or column-deactivation signal to bring into a floating state the associated row terminal or column terminal.

5. The system according to claim 4 wherein each of said row driving stages and column driving stages comprises:

a respective high-side transistor, coupled between the associated row terminal or column terminal and a respective high-voltage supply terminal configured to receive a high supply voltage; and

a respective low-side transistor coupled between the associated row terminal or column terminal and a respective low-voltage supply terminal configured to receive a low supply voltage; and

a control block configured to receive the respective row-deactivation or column-deactivation signal and to supply control signals to the respective high-side transistors and low-side transistors to switch off both said respective high-side transistors and low-side transistors and to bring into the floating state the associated row terminal or column terminal.

6. The system according to claim 5 wherein column driving stage includes a first unidirectional-conduction element, set between the associated column terminal and the respective high-side transistor and a recirculation circuit branch includes a second unidirectional current-conduction element in series with a recirculation transistor, which are coupled between the associated column terminal and the associated high-voltage supply terminal.

7. The system according to claim 5 wherein the row driving stage includes a first unidirectional-conduction element, set between the associated row terminal and the respective low-side transistor and a recirculation circuit branch includes a second unidirectional current-conduction element in series with a recirculation transistor, which are coupled between the associated row terminal and the associated low-voltage supply terminal.

8. The system according to claim 1 wherein the row and column driving stages associated with at least a same MEMS structure are configured, upon reception of the respective row-deactivation or column-deactivation signal to bring to a same voltage value the associated row terminal and column terminal in order to cause a zero potential difference at said MEMS structure.

9. The system according to claim 8 wherein said control unit is configured to enable the row-deactivation and column-deactivation signals associated with all the row and column driving stages during a condition of power-down of said MEMS array.

10. The system according to claim 8 wherein each of said row driving stages and column driving stages comprises:

a respective high-side transistor coupled between the associated row terminal or column terminal and a respective high-voltage supply terminal that is configured to receive a high supply voltage;

a respective low-side transistor coupled between the associated row terminal or column terminal and a respective low-voltage supply terminal that is configured to receive a low supply voltage; and

a control block configured to receive the respective row-deactivation or column-deactivation signal to supply control signals to the respective high-side transistors and low-side transistors; and

one between the row driving stage and column driving stage associated with a same MEMS structure further includes a deactivation stage, configured to be controlled to couple the associated row terminal or column terminal to the high-voltage supply terminal or low-voltage supply terminal of the other column driving stage or row driving stage.

11. The system according to claim 1, comprising a plurality of failure-detection stages, each associated with a respective one of said row driving stages and column driving stages and configured to detect and identify a presence of at least one failure associated with the corresponding MEMS structure.

12. The system according to claim 1 wherein:

said row driving stages are coupled to a high-voltage supply terminal configured to receive a high supply voltage and to a low-voltage supply terminal configured to receive a low supply voltage; and

said column driving stages are coupled to a respective high-voltage supply terminal configured to receive a respective high supply voltage and to a respective low-voltage supply terminal configured to receive a respective low supply voltage; and

a plurality of failure-detection stages coupled to said high-voltage supply terminals and low-voltage supply terminals and configured to detect a passage of a failure current associated with said terminals that indicates a condition of failure of one or more of the MEMS structures of said MEMS array.

13. The system according to claim 12 wherein said control unit, upon detection of said failure current by said failure-detection stages, is configured to:

supply the row-deactivation and column-deactivation signals to the respective row and column driving stages to deactivate the rows and columns of the MEMS array to cause interruption of the failure current; and

implement a procedure of identification of a position of the failure at said one or more of the MEMS structures of said MEMS array;

said identification procedure includes selective activation of each combination of row and column and identification of the position of the failure at the row and column combination that causes passage of the failure current.

14. The system according to claim 12 wherein each of said failure-detection stages includes:

a resistive detection element coupled to a respective high-voltage supply terminal or low-voltage supply terminal and is configured to be traversed by the failure current; and

a comparator block coupled to the resistive detection element and configured to compare a detection voltage indicating a voltage across said resistive detection element with a threshold voltage configured to supply a failure-detection signal.

15. The system according to claim 14 wherein said threshold voltage has an adjustable value;

and each of said failure-detection stages further includes a resistive adjustment element coupled in parallel to said resistive detection element and having a variable value of resistance;

said detection voltage is the voltage on an adjustment terminal of said resistive detection element.

16. The system according to claim 14 wherein said comparator block is configured to receive from said control unit a masking signal, configured to inhibit a corresponding comparison operation for a given time interval subsequent to a switch of said row-address or column-address signals.

17. The system according to claim 12 wherein said failure-detection stages are four in number and include:

a first failure-detection stage coupled in series to the current path towards the high-voltage supply terminal associated with said row driving stages and is configured to detect a failure current coming from said high-voltage supply terminal;

a second failure-detection stage coupled in series to the current path towards the low-voltage supply terminal associated with said row driving stages and is configured to detect a failure current coming from said low-voltage supply terminal;

a third failure-detection stage coupled in series to the current path towards the respective high-voltage supply terminal associated with said column driving stages and is configured to detect a failure current coming from said respective high-voltage supply terminal; and

a fourth failure-detection stage coupled in series to the current path towards the low-voltage supply terminal associated with said column driving stages and is configured to detect a failure current supplied to said respective low-voltage supply terminal.

18. A method for driving a MEMS array including a plurality of MEMS structures, each defining at least one row terminal and one column terminal, said method comprising:

supplying, by a plurality of row driving stages associated with said MEMS array, row-biasing signals to the row terminal of each MEMS structure associated with a respective row;

supplying, by a plurality of column driving stages associated with said MEMS array, column-biasing signals to the column terminal of each MEMS structure associated with a respective column; and

generating the row-biasing signals and column-address signals to the column driving stages for generation of the column-biasing signals by supplying, by a control unit, row-address signals to said row driving stages; and

causing deactivation of one or more rows and/or columns of said MEMS array by supplying row-deactivation or column-deactivation signals to one or more of said row and column driving stages.

19. The method according to claim 18, further comprising:

detecting a presence of at least one failure associated with one or more of said MEMS structures;

identifying a position of the failure at one or more of said MEMS structures; and

causing deactivation of the one or more rows or columns of said MEMS array corresponding to the position by enabling the respective row-deactivation or column-deactivation signals.

20. The method according to claim 18 wherein said MEMS array includes one or more redundancy rows and columns and activating one or more of said redundancy rows and columns occurs upon deactivation of the one or more rows and columns of said MEMS array.

21. The method according to claim 18 wherein causing deactivation comprises, by said row and column driving stages, following upon reception of the respective row-deactivation or column-deactivation signal, bringing the associated row terminal or column terminal into a floating state.

22. The method according to claim 19 wherein causing deactivation includes, by the row and column driving stages associated with at least a same MEMS structure, following upon reception of the respective row-deactivation or column-deactivation signal, causing a zero potential difference on said MEMS structure by bringing the associated row terminal and column terminal to a same voltage value.

23. The method according to claim 22 wherein causing deactivation includes enabling the row-deactivation and column-deactivation signals associated with all the row and column driving stages during a condition of power-down of said MEMS array.

24. The method according to claim 18 wherein said row driving stages are coupled to a high-voltage supply terminal configured to receive a high supply voltage and to a low-voltage supply terminal, configured to receive a low supply voltage;

and said column driving stages are coupled to a respective high-voltage supply terminal configured to receive a respective high supply voltage and to a respective low-voltage supply terminal configured to receive a respective low supply voltage; and

detecting a passage of a failure current associated with said high-voltage supply terminals or low-voltage supply terminals, indicating a condition of failure of one or more of the MEMS structures of said MEMS array.

25. The method according to claim 24, further comprising, following upon detecting of said failure current:

deactivating the rows and columns of the MEMS array by supplying row-deactivation and column-deactivation signals to the respective row and column driving stages, thus causing interruption of the failure current; and

implementing a procedure of identification of a position of the failure at said one or more of the MEMS structures of said MEMS array;

said identification procedure including selectively activating each combination of rows and columns and identifying the position of the failure at the row and column combination that causes passage of the failure current.