Digital sample clock generator, a vibration gyroscope circuitry comprising such digital sample clock generator, an associated apparatus, an associated semiconductor device and associated methods
A digital sample clock generator for generating a sample clock signal from an input signal derived from a drive measurement voltage signal of a vibrating MEMS gyroscope is provided.
1. A digital sample clock generator for generating a sample clock signal from an input signal derived from a drive measurement voltage signal of a vibrating MEMS gyroscope, the sample clock generator comprising:
an oscillator arranged to generate a master clock with a master clock period;
a synchronization unit arranged to detect a start of an input signal period of the input signal and to, upon detecting the start, generate a synchronization pulse in synchronization with the master clock;
a counter unit arrange to count master clock periods between subsequent synchronization pulses to obtain the number of master clock between subsequent synchronization pulses as a number count;
a multiplier arranged to multiply the number count with a pre-determined phase shift fraction to obtain a number of trim periods; and
a delay unit arranged to generate the sample clock signal with a clock signal period corresponding to the number count and with a delay relative to the synchronization pulse corresponding to the number of trim periods.
2. A digital sample clock generator according to claim 1 , the synchronization unit, the counter unit, the multiplier and the delay unit arranged to be clocked with the master clock.
3. A digital sample clock generator according to claim 2 , further comprising a count register arranged to store the number count, the count register comprising a latch input for receiving the synchronization pulse for latching the number count as stored in the count register to the multiplier upon receiving the synchronization pulse.
4. A digital sample clock generator according to claim 3 , the counter unit comprising a reset input for receiving the synchronization pulse, the counter unit being arranged to reset a counter upon receiving the synchronization pulse, to increment the counter at each master clock period and to store the counter in the count register.
5. A digital sample clock generator according to claim 1 , the multiplier being arranged to receive the pre-determined phase shift fraction from a user.
6. A digital sample clock generator according to claim 1 , the master clock having a master clock frequency in a range of 50-1000 times the frequency of the input signal.
7. A digital sample clock generator according to claim 6 , the frequency of the input signal being in a range of 1 kHz-100 kHz.
8. A vibration gyroscope circuitry comprising a first capacitance-to-voltage unit, a threshold detector, and a digital sample clock generator according to claim 1 , wherein
the first capacitance-to-voltage unit being arranged to provide a drive measurement voltage signal indicative of a displacement of a gyroscope mass along a drive axis of a vibrating MEMS gyroscope;
the threshold detector arranged to perform a threshold detection on the drive measurement voltage signal to obtain a digital signal; and
the digital sample clock generator arranged to receive the digital signal as the input signal and to generate the sample clock in dependence on a pre-determined in-phase phase shift fraction as an in-phase sample clock so as to obtain the in-phase sample clock in-phase with the drive measurement voltage signal.
9. A drive-mode vibration gyroscope circuitry comprising a vibration gyroscope circuitry according to claim 8 , a drive measurement signal sampler, a subtractor, an integrator and a variable gain amplifier, wherein
the drive measurement signal sampler being arranged to sample the drive measurement voltage signal with the in-phase sample clock to obtain envelope sample values;
the subtractor being arranged to subtract the envelope sample values from a pre-determined reference envelope amplitude to obtain a gain factor;
the integrator being arranged to integrate the drive measurement voltage signal to obtain an integrated drive measurement voltage signal; and
the variable gain amplifier being arranged to amplify the integrated drive measurement voltage signal with the gain factor to obtain a drive actuation voltage signal and to provide the a drive actuation voltage signal to a drive actuation unit of the vibration gyroscope.
10. A drive-mode vibration gyroscope circuitry according to claim 9 , the subtractor being arranged to receive the pre-determined reference envelope amplitude from a user.
11. A sense-mode vibration gyroscope circuitry comprising a vibration gyroscope circuitry according to claim 8 , a first sampler, a second capacitance-to-voltage unit and a sample processor, wherein
the second capacitance-to-voltage unit being arranged to provide a sense measurement voltage signal indicative of a displacement of the gyroscope mass along a sense axis, the sense axis being at a sense angle relative to the drive axis;
the first sampler being arranged to sample the sense measurement voltage signal with the in-phase sample clock to obtain in-phase sense sample values; and
a sample processor arranged to receive and process at least the in-phase sense sample values, the sample processor arranged to determine a measure of an angular rate in dependence on the in-phase sense sample values.
12. A sense-mode vibration gyroscope circuitry according to claim 11 , the sense-mode vibration gyroscope circuitry further comprising:
a second sampler, wherein
the second sampler being arranged to receive the digital signal as a quadrature sample clock and to sample the sense measurement voltage signal with the quadrature sample clock to obtain quadrature sense sample values, and
the sample processor arranged to receive and process the in-phase sense sample values and the quadrature sense sample values, the sample processor comprising a sample combiner arranged to determine the measure of an angular rate in dependence on the in-phase sense sample values and the quadrature sense sample values.
13. A sense-mode vibration gyroscope circuitry according to claim 11 , the sense-mode vibration gyroscope circuitry (VSCIRC) further comprising:
a further digital sample clock generator and a second sampler, wherein
the further digital sample clock generator arranged to receive the digital signal as the input signal and to generate the sample clock as an quadrature sample clock in dependence on a pre-determined quadrature phase shift fraction, the quadrature sample clock having a pre-determined quadrature phase shift relative to the drive measurement voltage signal, and
the second sampler being arranged to sample the sense measurement voltage signal with the quadrature sample clock to obtain quadrature sense sample values, and
the sample processor arranged to receive and process the in-phase sense sample values and the quadrature sense sample values, the sample processor comprising a sample combiner arranged to determine a measure of an angular rate in dependence on the in-phase sense sample values and the quadrature sense sample values.
14. A vibration gyroscope device comprising a vibration MEMS gyroscope and a vibration gyroscope circuitry comprising a drive-mode vibration gyroscope circuitry according to claim 9 .
15. A vibration gyroscope device according to claim 14 , the vibration MEMS gyroscope having a resonance frequency in a range of 1 kHz-100 kHz.
16. A semiconductor device comprising a digital sample clock generator according to claim 1 .
17. A method of generating a sample clock signal from an input signal, the method comprising:
generating a master clock with a master clock period,
generating a synchronization pulse from detecting a start of an input signal period of the input signal and, upon detecting the start, generating the synchronization pulse in synchronization with the master clock,
counting master clock periods between subsequent synchronization pulses to obtain the number of master clock periods between subsequent synchronization pulses as a number count,
determining a number of trim periods from multiplying the number count with a pre-determined phase shift fraction, and
generating the sample clock signal with a clock signal period corresponding to the number count and with a delay relative to the synchronization pulse corresponding to the number of trim periods.
18. The method according to claim 17 , further comprising:
obtaining a drive measurement voltage signal indicative of a displacement of a gyroscope mass along a drive axis of a vibrating MEMS gyroscope; and
performing a threshold detection on the drive measurement voltage signal to obtain a digital signal as the input signal.
19. A method of driving a vibration MEMS gyroscope, the method comprising:
generating a sample clock with a method as claimed in claim 18 using a pre-determined in-phase phase shift fraction as the pre-determined phase shift fraction;
sampling the drive measurement voltage signal with the in-phase sample clock to obtain envelope sample values;
subtracting the envelope sample values from a pre-determined reference envelope amplitude to obtain a gain factor;
integrating the drive measurement voltage signal to obtain an integrated drive measurement voltage signal; and
amplifying the integrated drive measurement voltage signal with the gain factor to obtain a drive actuation voltage signal and to provide the drive actuation voltage signal to a drive actuation unit of the vibration gyroscope.
20. A method of determining a measure of an angular rotation rate using a vibration MEMS gyroscope, the method comprising:
generating an in-phase sample clock using a method as claimed in claim 18 using a pre-determined in-phase phase shift fraction as the pre-determined phase shift fraction;
obtaining a sense measurement voltage signal indicative of a displacement of the gyroscope mass along a sense axis, the sense axis being at a sense angle relative to the drive axis;
sampling the sense measurement voltage signal with the in-phase sample clock to obtain in-phase sense sample values; and
determining the measure of the angular rate from at least the in-phase sense sample values.