OSCILLATOR DEVICE

• US 20110193449A1
• Filed: 10/08/2009
• Published: 08/11/2011
• Est. Priority Date: 10/08/2008
• Status: Active Grant

• Current Assignee: NXP B.V. (NXP Semiconductors NV)
• Original Assignee: NXP B.V. (NXP Semiconductors NV)
• Inventors: Van Beek, Jozef Thomas Martinus, Phan Le, Kim, Steeneken, Peter Gerard
• Granted Patent: US 8,717,111 B2
• Time in Patent Office: Days
• US Class Current: 310/317
• CPC Class Codes: G01C 19/56 Turn-sensitive devices using vibrating masses, e.g. vibratory angular rate sensors based on Coriolis forces
• CPC Class Codes: H03B 5/30 with frequency-determining element being electromechanical resonator

Abstract

An oscillator device comprises a resonator mass which is connected by a spring arrangement to a substrate and a feedback element for controlling oscillation of the resonator mass, which comprises a piezoresistive element connected between the resonator mass and the substrate. The invention provides an oscillator device in which the two parts (resonator and circuit to close the oscillation loop) are combined inside one single oscillator device, which can be a MEMS device.

Claims

1. An oscillator device, comprising:

a resonator mass connected by a spring arrangement to a substrate;

a feedback element for controlling oscillation of the resonator mass, which comprises a piezoresistive element connected to the resonator mass and which is arranged such that strain in the piezoresistive element varies in response to movement of the resonator mass, and a change in strain in the piezoresistive element causes a change in electrical resistance;

a driver for driving a current through the feedback element; and

an actuator for controlling the oscillation which includes terminals for driving the current through the feedback element.

2. An oscillator device as claimed in claim 1, wherein the driver comprises one of a current source and a voltage source for supplying, respectively, one of a current and a voltage to the piezoresistive element.

3. An oscillator device as claimed in claim 1, wherein the resonator mass is connected to the substrate by at least two arms which together form the spring arrangement, wherein a first arm comprises the piezoresistive element and a second arm comprises a current return path for the piezoresistive element.

4. An oscillator device as claimed in claim 3, further comprising two said resonator masses coupled together by the at least two arms, with a mid point of each arm being coupled to the substrate.

5. An oscillator device as claimed in claim 3, wherein the first, piezoresistive element arm is doped with a first doping level, and the second arm is doped with a second, higher doping level.

6. An oscillator device as claimed in claim 3, wherein the first, piezoresistive element arm is smaller in cross section than the second arm.

7. An oscillator device as claimed in claim 1, further comprising two said resonator masses coupled together by the feedback element which is in the form of a first arm, wherein each resonator mass has a respective second arm (136), one of which comprises a current input arm and the other of which comprises a current output arm.

8. An oscillator device as claimed in claim 1, wherein the resonator mass has rotational symmetry, with at least first and second feedback elements in the form of arms connecting the resonator mass to the substrate, at different angular positions around the resonator mass.

9. An oscillator device as claimed in claim 1, wherein the feedback element comprises at least two arms.

10. An oscillator device as claimed in claim 1, further comprising at least one output arm extending from the resonator mass, for providing an output voltage.

11. An oscillator device as claimed in claim 1, wherein the feedback element comprises a single arm arranged to bend, wherein opposite edges of the arm define a pair of piezoresistive elements.

12. An oscillator device as claimed in claim 1, wherein the resonator mass and the feedback element are at least a part of a single body.

13. An oscillator device as claimed in claim 1, wherein the resonator mass and the spring arrangement are at least a part of a single body.

14. An oscillator device as claimed in claim 1, wherein the resonator mass is a silicon body.

15. A method of generating an oscillating signal, comprising:

driving a current through a piezoresistive element using terminals which function as an actuator controlling oscillation;

controlling oscillation of a resonator mass using the piezoresistive element, which is arranged such that strain in the piezoresistive element varies in response to movement of the resonator mass, and a change in strain in the piezoresistive element causes a change in electrical resistance; and

sensing the a movement of the resonator mass to derive the oscillating signal.