Round robin sensing device and method of use
A round-robin sensing device is disclosed. The round-robin sensing device comprises a MEMS device, wherein the MEMS device includes first and second sense electrodes. The round-robin sensing device also comprises a multiplexer coupled to the first and second sense electrodes, at least one sense amplifier coupled to the multiplexer, a demodulator coupled to the at least one sense amplifier, and an integrate and dump circuit coupled to the demodulator. Finally, the round-robin sensing device comprises an analog-to-digital converter (ADC) coupled to the de-multiplexer, wherein the multiplexer, the at least one sense amplifier and the demodulator provide a continuous time sense path during amplification that is resettable and wherein the integrate and dump circuit and the ADC provide a discrete time processing path.
1. A sensing method comprising:
biasing a MEMS device at a fixed voltage;
receiving a first signal and a second signal from the MEMS device, wherein the first signal is associated with a first axis of the MEMS device and wherein the second signal is associated with a second axis of the MEMS device;
resetting a sense amplifier;
selecting the first signal or the second signal for amplification by the sense amplifier, wherein the selecting is concurrent with resetting the sense amplifier;
amplifying the selected signal, wherein a sampled error is added to the selected signal at an output of the sense amplifier to an error signal;
demodulating the error signal to form a demodulated signal; and
averaging the demodulated signal to form an averaged signal, wherein the averaging the demodulated signal substantially cancels the error signal.
2. The sensing method of claim 1 further comprising:
digitizing the averaged signal.
3. The sensing method of claim 2 further comprising:
demultiplexing the averaged signal to identify a first sensed signal associated with the first axis of the MEMS device.
4. The sensing method of claim 1 , wherein the first signal is selected to obtain sensed signal associated with the first axis and wherein the second signal is selected to obtain sensed signal associated with the second axis, and wherein the first signal and the second signal are selected in a round-robin fashion.
5. The sensing method of claim 1 further comprising:
cancelling a substantial portion of a quadrature portion of the selected signal through a feed-through capacitor coupled to the sense amplifier.
6. The sensing method of claim 1 , wherein the MEMS device is a gyroscope.
7. The sensing method of claim 6 , wherein the gyroscope comprises multi-axis sensing and one sensing circuit, wherein each signal associated with an axis of the gyroscope is sensed and read out one at a time and in a round-robin fashion.
8. A method comprising:
biasing a MEMS device at a fixed voltage;
receiving a first signal and a second signal from the MEMS device, wherein the first signal is associated with a first axis of the MEMS device and wherein the second signal is associated with a second axis of the MEMS device;
resetting a sense amplifier;
selecting the first signal concurrent with resetting the sense amplifier;
removing quadrature components of the first signal to form in-phase component of the first signal;
outputting the in-phase component of the first signal;
subsequent to outputting the in-phase component of the first signal, selecting the second signal concurrent with resetting the sense amplifier;
removing quadrature components of the second signal to form in-phase component of the second signal; and
outputting the in-phase component of the second signal.
9. The method of claim 8 , wherein removing quadrature components of the first signal and the second signal to form the in-phase component of the first signal and the second signal comprises:
amplifying the first signal and the second signal through another amplifier configured to cancel quadrature component of the first and the second signals.
10. The method of claim 8 further comprising:
adding a sampled error associated with the first signal to the in-phase component of the first signal to form an error signal;
demodulating the error signal to form a demodulated signal; and
averaging the demodulated signal to form an averaged signal, wherein the averaging the demodulated signal substantially cancels the error signal.
11. The method of claim 10 further comprising:
digitizing the averaged signal.
12. The method of claim 10 further comprising:
demultiplexing the averaged signal to form the in-phase component of the first signal associated with the first axis of the MEMS device.
13. The method of claim 8 further comprising:
adding a sampled error associated with the second signal to the in-phase component of the second signal to form an error signal;
demodulating the error signal to form a demodulated signal; and
averaging the demodulated signal to form an averaged signal, wherein the averaging the demodulated signal substantially cancels the error signal.
14. The method of claim 13 further comprising:
digitizing the averaged signal.
15. The method of claim 13 further comprising:
demultiplexing the averaged signal to form the in-phase component of the second signal associated with the second axis of the MEMS device.
16. The sensing method of claim 8 , wherein removing quadrature components of the first signal and the second signal is through a feed-through capacitor coupled to the sense amplifier.
17. The method of claim 8 , wherein the first signal and the second signal are selected in a round-robin fashion.