Abstract: Systems and methods for sensing angular motion using a microelectromechanical system (MEMS) gyroscope are described. These systems and methods may be useful for sensing angular motion in the presence of low-frequency noise, which may be noise below 1 KHz. In a system for sensing angular motion, low-frequency noise may give rise to duty cycle jitter, which may affect the demodulation of the sense signal and cause errors in angular motion estimates. The systems and methods described herein address this problem by relying on double-edge phase detection technique that involves sensing when the rising and falling edges of the resonator signal deviate from their expected values in the idealized 50% duty cycle scenario. To prevent the formation of ripples in the double-edge phase detection that may otherwise affect the demodulation of the sense signal, a switch may be used. The switch may be maintained in a non-conductive state when a ripple is received.

Abstract: A method for detecting frequency mismatch in microelectromechanical systems (MEMS) gyroscopes is described. Detection of the frequency mismatch between a drive signal and a sense signal may be performed by generating an output signal whose spectrum reflects the physical characteristics of the gyroscope, and using the output signal to determine the frequency fC of the sense signal. The output signal may be generated by cross-correlating a random or pseudo-random noise signal with a response signal, where the response signal can be obtained by allowing the noise signal to pass through a system designed to have a noise transfer function that mimics the frequency response of the gyroscope. Since the noise signal is random or pseudo-random, cross-correlating the noise signal with the response signal reveals spectral characteristics of the gyroscope. To improve computational efficiency, the cross-correlation can be performed on demodulated versions of the noise signal and the response signal.

Abstract: Circuits and methods for compensating microelectromechanical system (MEMS) gyroscopes for quality factor variations are described. Quality factor variations arise when mechanical losses are introduced in the gyroscope's resonator, for example due to thermoelastic damping or squeeze-film damping, which may hinder the gyroscope's ability to accurately sense angular velocity. Quality factor compensation may be performed by generating a compensation signal having a time decay rate that depends on the quality factor of resonator. In this way, artifacts that may otherwise arise in gyroscope's output are limited. Additionally, or alternatively, quality factor compensation may be performed by controlling the force with which the gyroscope's resonator is driven. This may be achieved, for example, by controlling the average value of the drive signal.

Abstract: Systems and methods for sensing angular motion using a microelectromechanical system (MEMS) gyroscope are described. These systems and methods may be useful for sensing angular motion in the presence of low-frequency noise, which may be noise below 1 KHz. In a system for sensing angular motion, low-frequency noise may give rise to duty cycle jitter, which may affect the demodulation of the sense signal and cause errors in angular motion estimates. The systems and methods described herein address this problem by relying on double-edge phase detection technique that involves sensing when the rising and falling edges of the resonator signal deviate from their expected values in the idealized 50% duty cycle scenario. To prevent the formation of ripples in the double-edge phase detection that may otherwise affect the demodulation of the sense signal, a switch may be used. The switch may be maintained in a non-conductive state when a ripple is received.

Abstract: Circuits and methods for compensating microelectromechanical system (MEMS) gyroscopes for quality factor variations are described. Quality factor variations arise when mechanical losses are introduced in the gyroscope's resonator, for example due to thermoelastic damping or squeeze-film damping, which may hinder the gyroscope's ability to accurately sense angular velocity. Quality factor compensation may be performed by generating a compensation signal having a time decay rate that depends on the quality factor of resonator. In this way, artifacts that may otherwise arise in gyroscope's output are limited. Additionally, or alternatively, quality factor compensation may be performed by controlling the force with which the gyroscope's resonator is driven. This may be achieved, for example, by controlling the average value of the drive signal.

Abstract: Systems and techniques are described for matching the resonance frequencies of multiple resonators. In some embodiments, a resonator generates an output signal reflecting the resonator's response to an input drive signal and an input noise signal. The output signal is then compared to the noise signal to derive a signal representative of the resonance frequency of the resonator. Comparing that signal to the output signal of a second resonator gives an indication of whether there is a difference between the resonance frequencies of the two resonators. If there is, one or both of the resonators may be adjusted. In this manner, the resonance frequencies of resonators may be matched during normal operation of the resonators.

Abstract: A method for detecting frequency mismatch in microelectromechanical systems (MEMS) gyroscopes is described. Detection of the frequency mismatch between a drive signal and a sense signal may be performed by generating an output signal whose spectrum reflects the physical characteristics of the gyroscope, and using the output signal to determine the frequency fC of the sense signal. The output signal may be generated by cross-correlating a random or pseudo-random noise signal with a response signal, where the response signal can be obtained by allowing the noise signal to pass through a system designed to have a noise transfer function that mimics the frequency response of the gyroscope. Since the noise signal is random or pseudo-random, cross-correlating the noise signal with the response signal reveals spectral characteristics of the gyroscope. To improve computational efficiency, the cross-correlation can be performed on demodulated versions of the noise signal and the response signal.

Abstract: Systems and techniques are described for matching the resonance frequencies of multiple resonators. In some embodiments, a resonator generates an output signal reflecting the resonator's response to an input drive signal and an input noise signal. The output signal is then compared to the noise signal to derive a signal representative of the resonance frequency of the resonator. Comparing that signal to the output signal of a second resonator gives an indication of whether there is a difference between the resonance frequencies of the two resonators. If there is, one or both of the resonators may be adjusted. In this manner, the resonance frequencies of resonators may be matched during normal operation of the resonators.

Abstract: In one aspect, a method of reducing power consumption in a circuit by adaptive bias current generation of a bias current configured to bias, at least in part, at least one amplifier of the circuit is provided. The method comprises establishing the bias current based, at least in part, on a reference frequency of a reference clock providing a clock signal to at least one component of the circuit, and changing the bias current in response to a change in the reference frequency of the at least one reference clock, the bias current being change non-linearly with respect to the change in the reference frequency of the at least one reference clock. In another aspect, the method comprises establishing the bias current based, at least in part, on a capacitance of a reference capacitor, and changing the bias current in response to a change in the capacitance of the reference capacitor such that the bias current is changed non-linearly with respect to changes in the capacitance of the reference capacitor.

Abstract: An apparatus and method for inter-channel data exchange in multi-channel data acquisition systems is disclosed. A multi-channel data acquisition system may include a data exchange layer coupling two or more channels of the data acquisition system. Data may be transmitted via the data exchange layer between the channels, enabling data from one channel to be processed and output by another channel. The data exchange layer may include a serial exchange layer or a parallel exchange layer.

Abstract: In one aspect, a method of reducing power consumption in a circuit by adaptive bias current generation of a bias current configured to bias, at least in part, at least one amplifier of the circuit is provided. The method comprises establishing the bias current based, at least in part, on a reference frequency of a reference clock providing a clock signal to at least one component of the circuit, and changing the bias current in response to a change in the reference frequency of the at least one reference clock, the bias current being change non-linearly with respect to the change in the reference frequency of the at least one reference clock. In another aspect, the method comprises establishing the bias current based, at least in part, on a capacitance of a reference capacitor, and changing the bias current in response to a change in the capacitance of the reference capacitor such that the bias current is changed non-linearly with respect to changes in the capacitance of the reference capacitor.

Abstract: In one aspect, a method of reducing power consumption in a circuit by adaptive bias current generation of a bias current configured to bias, at least in part, at least one amplifier of the circuit is provided. The method comprises establishing the bias current based, at least in part, on a reference frequency of a reference clock providing a clock signal to at least one component of the circuit, and changing the bias current in response to a change in the reference frequency of the at least one reference clock, the bias current being change non-linearly with respect to the change in the reference frequency of the at least one reference clock. In another aspect, the method comprises establishing the bias current based, at least in part, on a capacitance of a reference capacitor, and changing the bias current in response to a change in the capacitance of the reference capacitor such that the bias current is changed non-linearly with respect to changes in the capacitance of the reference capacitor.

Abstract: The invention is directed to an interface circuit for bridging voltage domains. The interface circuit receives an input signal, having a larger voltage domain, and safely provides the signal to an electronic device which has a smaller voltage domain. The interface circuit may include a transistor configured as a source follow so that an output of the transistor follows the input of the transistor. A blocking voltage may be provided at the input of the transistor to provide a voltage bias, blocking a range of input voltages to the transistor. The transistor may also have a blocking voltage at a drain terminal of the transistor, to block any output voltage above the blocking voltage.

Abstract: Two or more buffers may configured and arranged such that a quiescent current that flows through and biases a first buffer also flows through and biases a second buffer. The first and second buffers may, for example, be source followers used as reference buffers that drive inputs of a switched-capacitor circuit.

Abstract: In one aspect, a resistor process invariant transconductor is provided. The transconductor comprises a voltage input configured to receive at least one voltage signal, a current output configured to provide at least one current signal, wherein a ratio between the at least one voltage signal and the least one current signal forms a total transconductance for the transconductor, and a circuit including at least one integrated resistor connected between the voltage input and the current output, the circuit adapted to maintain the total transconductance substantially constant across variation of the at least one integrated resistor.

Abstract: The invention is directed to an interface circuit for bridging voltage domains. The interface circuit receives an input signal, having a larger voltage domain, and safely provides the signal to an electronic device which has a smaller voltage domain. The interface circuit may include a transistor configured as a source follow so that an output of the transistor follows the input of the transistor. A blocking voltage may be provided at the input of the transistor to provide a voltage bias, blocking a range of input voltages to the transistor. The transistor may also have a blocking voltage at a drain terminal of the transistor, to block any output voltage above the blocking voltage.

Abstract: An apparatus and method for inter-channel data exchange in multi-channel data acquisition systems is disclosed. A multi-channel data acquisition system may include a data exchange layer coupling two or more channels of the data acquisition system. Data may be transmitted via the data exchange layer between the channels, enabling data from one channel to be processed and output by another channel. The data exchange layer may include serial or parallel communication means.

Abstract: In one embodiment, a circuit comprises at least first and second circuit stages, at least one level shifting circuit, and a control circuit. The first circuit stage is configured and arranged to produce a reference voltage at the at least one first output during each first phase of at least first and second phases, and to produce an output signal at the at least one first output that is responsive to an input signal at the at least one first input during each second phase of the at least first and second phases. The at least one level shifting circuit comprises at least one capacitor and at least one switch and is coupled between the first circuit stage and the second circuit stage.

Abstract: In one aspect, a method of reducing power consumption in a circuit by adaptive bias current generation of a bias current configured to bias, at least in part, at least one amplifier of the circuit is provided. The method comprises establishing the bias current based, at least in part, on a reference frequency of a reference clock providing a clock signal to at least one component of the circuit, and changing the bias current in response to a change in the reference frequency of the at least one reference clock, the bias current being change non-linearly with respect to the change in the reference frequency of the at least one reference clock. In another aspect, the method comprises establishing the bias current based, at least in part, on a capacitance of a reference capacitor, and changing the bias current in response to a change in the capacitance of the reference capacitor such that the bias current is changed non-linearly with respect to changes in the capacitance of the reference capacitor.

Abstract: Methods and apparatus for reducing the thermal noise integrated on a storage element are disclosed. One embodiment of the invention is directed to a sampling circuit comprising a sampling capacitor to store a charge, the sampling capacitor being exposed to an ambient temperature. The sampling circuit further comprises circuitry to sample the charge onto the capacitor, wherein thermal noise is also sampled onto the capacitor, and wherein the circuitry is constructed such that the power of the thermal noise sampled onto the capacitor is less than the product of the ambient temperature and Boltzmann's constant divided by a capacitance of the sampling capacitor. Another embodiment of the invention is directed to a method of controlling thermal noise sampled onto a capacitor. The method comprises an act of independently controlling the spectral density of the thermal noise and/or the bandwidth of the thermal noise.