Micromechanical apparatus with limited actuation bandwidth

United States Patent m

Lewis

[54] MICROMECHANICAL APPARATUS WITH LIMITED ACTUATION BANDWIDTH

[75] Inventor: Stephen R. Lewis, Reading, Mass.

[73] Assignee: Analog Devices, Inc., Norwood, Mass.

[21] Appl. No.: 359,520
[22] Filed: Dec. 20,1994

[51] Int. CI.6 G01P 15/00

[52] U.S. CI 73/514.18; 73/1 DV; 73/862.61;

73/514.32

[58] Field of Search 73/517 B, 517 R,

73/862.61, 701, 1 D, 1 DV, 514.18, 514.32; 324/661, 662, 678; 361/280, 283.1

[56] References Cited

U.S. PATENT DOCUMENTS

3,120,622 2/1964 Dranetz et al 310/8.4

4,922,756 5/1990 Henrion 73/517

5,060,504 10/1991 White et al 73/1 D

5,103,667 4/1992 Allen et al 73/1 D

5,253,510 10/1993 Allen et al 73/1 D

5,314,572 5/1994 Core et al 156/643

5,326,726 7/1994 Tsang et al 437/228

5,345,824 9/1994 Sherman et al 73/517 B

5,364,497 11/1994 Chau et al 156/645

5,433,101 7/1995 Spangler et al 73/1 D

5,445,006 8/1995 Allen et al 73/1 D

5,447,051 9/1995 Hanks et al 73/1 D

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US005583290A [ii] Patent Number: 5,583,290 [45] Date of Patent: Dec. 10,1996

5,465,604 11/1995 Sherman 73/1 DV

5,492,020 2/1996 Okada 73/862.626

FOREIGN PATENT DOCUMENTS

59-95266 6/1984 Japan .
63-85461 4/1988 Japan .

Primary Examiner—Hezxon E. Williams
Assistant Examiner—Richard A. Moller
Attorney, Agent, or Firm—Wolf, Greenfield & Sacks, P.C.

[57] ABSTRACT

A micromechanical sensing apparatus includes a micromechanical sensor having a stationary element and a movable element which are electrically conductive, and a sensing circuit responsive to the micromechanical sensor for generating an output indicative of a sensed quantity. The sensing circuit may have a closed loop configuration or an open loop configuration. The sensing apparatus further includes an actuation circuit for applying to the micromechanical sensor an actuation signal, such as a test signal, for electrostatically deflecting the movable element relative to stationary element. The actuation circuit includes circuitry for limiting the bandwidth of the actuation signal such that the deflection of the movable element does not exceed maximum deflection limits. In the closed loop configuration, the bandwidth of the actuation signal is preferably limited to less than or equal to the closed loop bandwidth of the sensing circuit. As a result, electrostatic capture and/or contact between the movable element and the stationary element is prevented.

26 Claims, 4 Drawing Sheets