Capacitance detector for accelerometer and gyroscope and accelerometer and gyroscope with capacitance detector

Abstract

A capacitance-to-frequency converter is configured to convert a difference between first and second capacitances produced of a teeter-totter capacitive transducer as a result of a rotational force being applied to the teeter-totter capacitive transducer to a first signal having a first frequency that is a function of the rotational force, and to convert a sum of the first and second capacitances produced as a result of an acceleration force to a second signal having a second frequency that is a function of the acceleration force. The capacitance-to-frequency converter includes a first oscillator having a first oscillator frequency that changes in response to a change in the first capacitance; a second oscillator having a second oscillator frequency that changes in response to a change in the second capacitance; and a mixer having first and second mixer inputs connected outputs of the first and

1 . A method, comprising:
 providing a device, comprising:
 a first input configured to be connected to a first capacitor of a teeter-totter capacitive transducer, the first capacitor having a first capacitance, and 
 a second input configured to be connected to a second capacitor of the teeter-totter capacitive transducer, the second capacitor having a second capacitance; 
   converting a difference between the first and second capacitances produced as a result of a rotational force being applied to the teeter-totter capacitive transducer to a first signal having a first frequency that is a function of the rotational force; and   converting a sum of the first and second capacitances produced as a result of an acceleration force being applied to the teeter-totter capacitive transducer to a second signal having a second frequency that is a function of the acceleration force.   
     
     
         2 . The method of  claim 1 , wherein converting the difference between the first and second capacitances to the first signal, and converting the sum of the first and second capacitances to the second signal, comprises:
 connecting the first input of the device to a first oscillator, including a first acoustic resonator, such that a first oscillator frequency of the first oscillator changes in response to a change in the first capacitance;   connecting the second input of the device to a second oscillator, including a second acoustic resonator, such that a second oscillator frequency of the second oscillator changes in response to a change in the second capacitance; and   generating the first signal having the first frequency as a difference between the second oscillator frequency and the first oscillator frequency.   
     
     
         3 . The method of  claim 2 , further comprising producing the second signal having the second frequency as a sum of the second oscillator frequency and the first oscillator frequency. 
     
     
         4 . The method of  claim 3 , further comprising mixing the second signal with an output signal of a third oscillator to produce a third signal having a third frequency that is a function of the acceleration force. 
     
     
         5 . The method of  claim 2 , further comprising providing the first oscillator including the first acoustic resonator and the second oscillator including the second acoustic resonator in a packaged device, the packaged device comprising:
 a base substrate having a first bonding pad and a peripheral pad provided thereon, the peripheral pad encompassing the first bonding pad;   a lid substrate having a bonding pad seal and a peripheral pad seal provided thereon, the bonding pad seal bonding around the perimeter of the first bonding pad and the peripheral pad seal bonding with the peripheral pad to define a hermetically sealed volume between the lid substrate and the base substrate, the lid substrate defining a through hole therein positioned over the first bonding pad, the through hole providing access for an electrical connection to the first bonding pad; and   electronic circuitry provided on a portion of a first surface of the lid substrate within the hermetically sealed volume,   wherein the first acoustic resonator and the second acoustic resonator are disposed on the base substrate, and   wherein electronic circuitry includes:
 first oscillator circuitry electrically connected with the first acoustic resonator to form the first oscillator, and 
 second oscillator circuitry electrically connected with the second acoustic resonator to form the second oscillator. 
   
     
     
         6 . A device, comprising:
 a first input configured to be connected to a first capacitor of a teeter-totter capacitive transducer, the first capacitor having a first capacitance;   a second input configured to be connected to a second capacitor of the teeter-totter capacitive transducer, the second capacitor having a second capacitance; and   a capacitance-to-frequency converter configured to convert a difference between the first and second capacitances produced as a result of a rotational force being applied to the teeter-totter capacitive transducer to a first signal having a first frequency that is a function of the rotational force, and to convert a sum of the first and second capacitances produced as a result of an acceleration force being applied to the teeter-totter capacitive transducer to a second signal having a second frequency that is a function of the acceleration force.   
     
     
         7 . The device of  claim 6 , wherein the capacitance-to-frequency converter comprises:
 a first oscillator having a first oscillator frequency that changes in response to a change in the first capacitance;   a second oscillator having a second oscillator frequency that changes in response to a change in the second capacitance;   a mixer having first and second mixer inputs connected respectively to an output of the first oscillator and to an output of the second oscillator; and   a diplexer having an input connected to an output of the mixer and having first and second diplexer outputs, wherein the first diplexer output provides the first signal having the first frequency, and wherein the second diplexer output provides the second signal having the second frequency.   
     
     
         8 . The device of  claim 7 , further comprising:
 a packaged device, comprising:
 a base substrate having a first bonding pad and a peripheral pad provided thereon the peripheral pad encompassing the first bonding pad; 
 a lid substrate having a bonding, pad seal and a peripheral pad seal provided thereon, the bonding pad seal bonding around the perimeter of the first bonding pad and the peripheral pad seal bonding with the peripheral pad to define a hermetically sealed volume between the lid substrate and the base substrate, the lid substrate defining a through hole therein positioned over the first bonding pad, the through hole providing access for an electrical connection to the first bonding pad; 
 a first acoustic resonator and a second acoustic resonator disposed on the base substrate; and 
 electronic circuitry provided on a portion of a first surface of the lid substrate within the hermetically sealed volume, the electronic circuitry including:
 first oscillator circuitry electrically connected with the first acoustic resonator to form the first oscillator, 
 second oscillator circuitry electrically connected with the second acoustic resonator to form the second oscillator, and 
 the mixer. 
 
   
     
     
         9 . The device of  claim 7 , wherein the capacitance-to-frequency converter further comprises:
 a third oscillator;   a second mixer having a first input connected to an output of the third oscillator, a second input connected to the second diplexer output, and an output; and   a low pass filter having an input connected to the output of the second mixer and outputting a third signal having a third frequency that is a function of the rotational force applied to the device.   
     
     
         10 . The device of  claim 6 , further comprising:
 a third input configured to be connected to a first capacitor of a second teeter-totter capacitive transducer, the first capacitor of the second teeter-totter capacitive transducer having a third capacitance;   a fourth input configured to be connected to a second capacitor of the second teeter-totter capacitive transducer, the second capacitor of the second teeter-totter capacitive transducer having a fourth capacitance;   a fifth input configured to be connected to a first capacitor of a third teeter-totter capacitive transducer, the first capacitor of the third teeter-totter capacitive transducer having a fifth capacitance;   a sixth input configured to be connected to a second capacitor of the third teeter-totter capacitive transducer, the second capacitor of the third teeter-totter capacitive transducer having a sixth capacitance;   a second capacitance-to-frequency converter configured to convert, a difference between the third and fourth capacitances produced as a result of a second rotational force being applied to the teeter-totter capacitive transducer to a third signal having a third frequency that is a function of the second rotational force; and   a third capacitance-to-frequency converter configured to convert a difference between the fifth and sixth capacitances produced as a result of a third rotational force being applied to the teeter-totter capacitive transducer to a fourth signal having a fourth frequency that is a function of the third rotational force,   wherein the capacitance-to-frequency converter, the second capacitance-to-frequency converter, and the third capacitance-to-frequency converter are configured to detect the rotational force, the second rotational force, and the third rotational force applied in three mutually orthogonal planes.   
     
     
         11 . The device of  claim 8 , the lid substrate comprising a semiconductor material, wherein the portion of first surface of the lid substrate has a substantially lower resistivity that a resistivity of the semiconductor material. 
     
     
         12 . A device, comprising:
 a first input configured to be connected to a first capacitor of a teeter-totter capacitive transducer, the first capacitor having a first capacitance;   a second input configured to be connected to a second capacitor of the teeter-totter capacitive transducer, the second capacitor having a second capacitance;   a capacitance-to-frequency converter configured to convert a difference between the first and second capacitances produced as a result of a rotational force being applied to the teeter-totter capacitive transducer to a first signal having a first frequency that is a function of the rotational force, and to convert a sum of the first and second capacitances produced as a result of an acceleration force being applied to the teeter-totter capacitive transducer to a second signal having a second frequency that is a function of the acceleration force; and   a frequency detection block configured to detect the first and second frequencies of the first and second signals.   
     
     
         13 . The device of  claim 12 , wherein the frequency detection block is configured to provide a rotational force detection signal that indicates the rotational force being applied to the teeter-totter capacitive transducer. 
     
     
         14 . The device of  claim 12 , wherein the teeter-totter capacitive transducer comprises a microelectromechanical system (MEMs) device. 
     
     
         15 . The device of  claim 12 , wherein the frequency detection block comprises a frequency counter for each of the first and second signals. 
     
     
         16 . The device of  claim 12 , wherein the frequency detection block comprises frequency detector. 
     
     
         17 . The device of  claim 16 , wherein the frequency detector comprises a frequency discriminator, or a phase-lock loop (PLL) frequency detector 
     
     
         18 . The device of  claim 16 , wherein the device comprises:
 a packaged device, comprising:
 a base substrate having a first bonding pad and a peripheral pad provided thereon, the peripheral pad encompassing the first bonding pad; 
 a lid substrate having a bonding pad seal and a peripheral pad seal provided thereon, the bonding pad seal bonding around the perimeter of the first bonding pad and the peripheral pad seal bonding with the peripheral pad to define a hermetically sealed volume between the lid substrate and the base substrate, the lid substrate defining a through hole therein positioned over the first bonding pad, the through hole providing access for an electrical connection to the first bonding pad; 
 a bulk acoustic wave (BAW) resonator disposed over the base substrate; and 
 electronic circuitry provided on a portion of a first surface of the lid substrate within the hermetically sealed volume. 
   
     
     
         19 . The device of  claim 18 , further comprising a second BAW resonator, wherein a first oscillator comprises the first BAW resonator and a second oscillator comprises the second BAW resonator. 
     
     
         20 . The device of  claim 19 , wherein the first and second BAW resonators are one of a film bulk acoustic resonator (FBAR) or a surface mounted resonator (SMR). 
     
     
         21 . The device of  claim 18 , wherein the base substrate comprises a recessed region configured to receive a pedestal disposed over the lid substrate, the pedestal comprising the electrical circuitry. 
     
     
         22 . The device of  claim 18 , the lid substrate comprising a semiconductor material, the lid substrate further comprising a low-resistivity material layer region disposed over the lid substrate, the low-resistivity material layer region comprising a resistivity that is substantially lower than a resistivity of the semiconductor material. 
     
     
         23 . The device of  claim 22 , wherein the electronic circuitry is disposed in the low-resistivity material layer region, or over the low-resistivity material layer region, or both. 
     
     
         24 . The device of  claim 22 , the lid substrate further comprising an electrically insulating material disposed to substantially electrically isolate the from an electrically conductive layer in contact with a bonding pad seal. 
     
     
         25 . The device of  claim 22 , wherein the BAW resonator is electrically connected to the electronic circuitry. 
     
     
         26 . A packaged device, comprising:
 a base substrate having a first bonding pad and a peripheral pad provided thereon, the peripheral pad encompassing the first bonding pad;   a lid substrate having a bonding pad seal and a peripheral pad seal provided thereon, the bonding pad seal bonding around the perimeter of the first bonding pad and the peripheral pad seal bonding with the peripheral pad to define a hermetically sealed volume between the lid substrate and the base substrate, the lid substrate defining a through hole therein positioned over the first bonding pad, the through hole providing access for an electrical connection to the first bonding pad;   a bulk acoustic wave (BAW) resonator disposed over the base substrate; and   electronic circuitry provided on a portion of a first surface of the lid substrate within the hermetically sealed volume.   
     
     
         27 . The packaged device of  claim 26 , wherein the base substrate comprises a recessed region configured to receive a pedestal disposed over the lid substrate, the pedestal comprising the electrical circuitry. 
     
     
         28 . The packaged device of  claim 26 , the lid substrate comprising a semiconductor material, the lid substrate further comprising a low-resistivity material layer region disposed over the lid substrate, the low-resistivity material layer region comprising a resistivity that is substantially lower than a resistivity of the semiconductor material. 
     
     
         29 . The packaged device of  claim 28 , wherein the electronic circuitry is disposed in the low-resistivity material layer region, or over the low-resistivity material layer region, or both. 
     
     
         30 . The packaged device of  claim 28 , the lid substrate further comprising an electrically insulating material disposed to substantially electrically isolate the from electrically conductive layer in contact with a bonding pad seal. 
     
     
         31 . The packaged device of  claim 28  wherein the BAW resonator is electrically connected to the electronic circuitry.