Variable capacitance electronic device and microelectromechanical device incorporating such electronic device

• US 8,667,842 B2
• Filed: 12/06/2012
• Issued: 03/11/2014
• Est. Priority Date: 12/11/2008
• Status: Active Grant

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Prandi, Luciano
• Primary Examiner(s): KWOK, HELEN C
• Application Number:
  US13/707,389
• Publication Number:
  US 20130170091A1
• Time in Patent Office: 460 Days
• Field of Search: 735/041.2, 735/041.4, 735/040.2, 735/040.4, 735/143.2, 735/040.8
• US Class Current: 73/504.12
• CPC Class Codes: G01C 19/5726 Signal processing
• CPC Class Codes: G01C 19/5755 the devices having a single sensing mass
• CPC Class Codes: H01G 7/06 having a dielectric selected for the variation of its permittivity with applied voltage, i.e. ferroelectric capacitors electrets H01G7/02
• CPC Class Codes: Y10T 29/49826 Assembling or joining

Abstract

An electronic device includes a capacitive component with variable capacitance coupled to a control stage that controls the capacitance, based on a reference signal, with a reference frequency, and an excitation signal, that is a multiple of the reference frequency. The capacitive component includes a variable capacitive network having a plurality of switched capacitors, each being switchable between a first configuration, where it is connected between connection terminals of the capacitive component, and a second configuration, where it is connected at most to one of the connection terminals. The control stage includes a logic module, coupled to the variable capacitive network for switching periodically each capacitor between the first configuration and the second configuration. A sign circuit, coupled to the capacitive component supplies a control signal having edges concordant with the excitation signal in one half-period of each cycle of the reference signal and discordant edges in the other half-period.

Claims

1. A method, comprising:

retrieving a first calibration signal and a second calibration signal from a storage device in a control stage of a micro-electromechanical system, the system including a sensor having a first output and a second output, the control stage being coupled to the first and second outputs of the sensor;

providing the first calibration signal to a first calibration network in the control stage and providing the second calibration signal to a second calibration network in the control stage;

providing a first compensation drive signal to the first calibration network and providing a second compensation drive signal to the second calibration network;

generating a first differential compensation charge packet from the first calibration network and generating a second differential compensation charge packet from the second calibration network; and

compensating for quadrature errors in the system with the first and second differential compensation charge packets.

2. The method of claim 1, further comprising:

generating the first compensation drive signal from an excitation signal and generating the second compensation drive signal from the excitation signal.

3. The method of claim 2, further comprising:

generating a first sign-control signal in the control stage and generating a second sign-control signal in the control stage;

generating the first compensation drive signal from the excitation signal and the first sign-control signal and generating the second compensation drive signal from the excitation signal and the second sign-control signal.

4. The method of claim 1 wherein the compensating for quadrature errors further includes injecting the first differential compensation charge packet into the first output of the sensor and extracting the second differential compensation charge packet from the second output of the sensor.

5. The method of claim 1, further comprising:

receiving a reference signal in the control stage, the reference signal having a reference frequency;

generating an excitation signal in the control stage, the excitation signal having an excitation frequency that is a multiple of the reference frequency; and

generating the first compensation drive signal from the excitation signal and generating the second compensation drive signal from the excitation signal.

6. A micro-electromechanical system, comprising:

a sensor having an input and a first and a second output;

a control stage coupled to the first and the second output of the sensor, the control stage including;

a storage module configured to store and provide a first calibration signal and a second calibration signal;

a first capacitive network coupled to the first output of the sensor, the first capacitive network configured to receive the first calibration signal and to generate a first compensation charge packet, the first compensation charge packet being configured to cancel quadrature errors associated with the first output;

a second capacitive network coupled to the second output of the sensor, the second capacitive network being configured to receive the second calibration signal and to generate a second compensation charge packet, the second compensation charge packet being configured to cancel quadrature errors associated with the second output.

7. The system of claim 6 wherein the control stage includes:

a generator module configured to generate an excitation signal from a reference signal, the reference signal having a reference frequency and the excitation signal having an excitation frequency that is a multiple of the reference frequency;

a first sign circuit configured to generate a first compensation drive signal from the excitation signal and a first sign-control signal, the first capacitive network being configured to receive the first compensation drive signal; and

a second sign circuit configured to generate a second compensation drive signal from the excitation signal and a second sign-control signal, the second capacitive network being configured to receive the second compensation drive signal.

8. The system of claim 7, further comprising a charge amplifier module having a first input and a second input, the first input of the charge amplifier being coupled to the first input of the sensor and the second input of the charge amplifier being coupled to the second input of the sensor.

9. The system of claim 8 wherein the charge amplifier module includes a third input, the first and the second capacitive network being coupled to the third input.

10. The system of claim 9 wherein the charge amplifier module includes:

a first capacitor coupled between the first input and a first output of the charge amplifier module; and

a second capacitor coupled between the second input and a second output of the charge amplifier module.