Method and Apparatus for MEMS Phase Locked Loop
AssigneeAnalog Devices, Inc.
InventorsAbhinav Kumar Dikshit, Gadam Chetty Deva Phanindra Kumar, Anjan Kumar Krishnaswamy
Life of this patent
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Abstract
The proper operation of a phase locked loop is determined by monitoring certain signals within the loop for their phase relationship or duty cycle. If a malfunction of the loop is detected, proper operation may be imposed or restored by resetting a phase-frequency detector, or by flipping the output of the phase-frequency detector.
Claims20
A method of driving an oscillating member, the method comprising:
- applying a drive signal to the oscillating member, the drive signal having a drive frequency;
- providing a first reference signal indicative of the phase shift imparted on the drive signal by the oscillating member;
- decreasing the drive frequency if the phase shift is less than ninety degrees, and increasing the drive frequency if the phase shift is between ninety and one hundred eighty degrees.
A method of addressing positive feedback in a circuit driving an oscillating member, the method comprising:
- applying a drive signal having a drive frequency to the oscillating member;
- providing a first reference signal to a phase detector, the first reference signal indicative of the phase shift imparted on the drive signal by the oscillating member;
- providing a second reference signal to the phase detector, the second signal having the same frequency as the drive signal, but leading the drive signal by ninety degrees;
- generating a first control signal if a phase detector determines that the first reference signal leads the second reference signal;
- and
- resetting the phase detector if the first control signal is active at a falling edge of the second reference signal.
A method of driving an oscillating member using a phase locked loop, comprising:
- applying a drive signal having a drive frequency to the oscillating member;
- providing a reference signal indicative of the phase shift imparted on the drive signal by the oscillating member;
- comparing the phase of the drive signal to the reference signal in a phase detector;
- generating a first control signal if the reference signal lags the drive signal;
- and
- determining whether the duty cycle of the first control signal exceeds a predetermined percent;
- and
- increasing the frequency of the drive signal if the duty cycle of the first control signal exceeds the predetermined percent.
A method of driving an oscillating member using a driver, wherein the driver provides a drive signal to the oscillating member, the drive signal having a drive frequency, the method comprising:
- determining whether the oscillating member is oscillating above a desired frequency;
- determining whether the driver is increasing the drive frequency;
- and
- resetting the driver if the oscillating member is oscillating above a desired frequency and the driver increasing the drive frequency.
A method of driving an oscillating member using a driver, wherein the driver provides a drive signal to the oscillating member, the drive signal having a drive frequency, the method comprising:
- determining whether the oscillating member is oscillating below a desired frequency;
- determining whether the driver is decreasing the drive frequency;
- and
- resetting the driver if the oscillating member is oscillating above a desired frequency and the driver decreasing the drive frequency.
A circuit for driving an oscillating member, comprising:
- a variable-frequency oscillator having an oscillator output;
- an arrival-time detector having a first arrival-time detector input and a second arrival-time detector input, an up output and a down output, and a reset input, the first arrival-time detector input coupled to the oscillator output;
- a phase shifter having an phase shifter input and a phase shifter output, the phase shifter input coupled to the oscillator output;
- an oscillating member having a member input and a member output, the member input coupled to the phase shifter output, and the member output coupled to the second arrival-time detector input;
- an error detector having a first error detector input coupled to the up output of the arrival-time detector, and a second error detector input coupled to the down output of the arrival-time detector, and an error detector output coupled to the reset input of the arrival-time detector.
A method of driving an oscillating member using a phase locked loop, the method comprising:
- applying a drive signal having a drive frequency to the oscillating member;
- providing a first reference signal to a phase detector, the first reference signal indicative of the phase shift imparted on the drive signal by the oscillating member;
- providing a second reference signal to the phase detector, the second signal having the same frequency as the drive signal, but leading the drive signal by ninety degrees;
- generating a first control signal if a phase detector determines that the first reference signal leads the second reference signal, and generating a second control signal if a phase detector determines that the first reference signal lags the second reference signal;
- and
- transposing at least one of the first control signal and the second control signal is active at a falling edge of the drive signal.
Dependencies are inferred from the claim text.