Clock generator with dual-path temperature compensation
In a timing signal generator having a resonator, one or more temperature-sense circuits generate an analog temperature signal and a digital temperature signal indicative of temperature of the resonator. First and second temperature compensation signal generators to generate, respectively, an analog temperature compensation signal according to the analog temperature signal and a digital temperature compensation signal according to the digital temperature signal. Clock generating circuitry drives the resonator into mechanically resonant motion and generates a temperature-compensated output timing signal based on the mechanically resonant motion, the analog temperature compensation signal and the digital temperature compensation signal.
1. A timing signal generator comprising:
a microelectromechanical systems (MEMS) resonator, wherein the MEMS resonator is to vibrate at a resonant frequency having a temperature dependent variation;
temperature sensing circuitry, including at least one temperature sensor, the temperature sensing circuitry to generate each of an analog temperature-dependent signal and a digital temperature-dependent signal;
circuitry to control a frequency of operation of the MEMS resonator as a function of sensed temperature using a first one of the analog temperature-dependent signal and the digital temperature-dependent signal; and
locked-loop circuitry to receive a signal representing a resonance frequency of the MEMS resonator and to control generation a timing signal therefrom, for output by the timing signal generator, using a second one of the analog temperature-dependent signal and the digital temperature-dependent signal.
2. The timing signal generator of claim 1 wherein the at least one temperature sensor comprises a thermistor.
3. The timing signal generator of claim 1 wherein the at least one temperature sensor comprises two MEMS resonators, and wherein the temperature sensing circuitry is to generate the digital temperature-dependent signal as a function of divergence of respective sensed resonance frequencies of the two MEMS resonators.
4. The timing signal generator of claim 1 wherein the circuitry to control the frequency of operation is to generate a bias voltage to be applied to the MEMS resonator as a function of the first one of the analog temperature-dependent signal and the digital temperature-dependent signal.
5. The timing signal generator of claim 4 wherein the first one is the digital temperature-dependent signal.
6. The timing signal generator of claim 4 wherein the first one is the analog temperature-dependent signal.
7. The timing signal generator of claim 4 wherein the timing signal generator further comprises a memory, wherein the memory is to store programmed polynomial coefficients for frequency correction, and wherein the circuitry to control the frequency of operation is to generate the bias voltage to be applied to the MEMS resonator using the programmed polynomial coefficients.
8. The timing signal generator of claim 7 wherein the circuitry to control the frequency of operation comprises an analog multiplier and wherein the circuitry to control the frequency of operation is to configure the analog multiplier to apply the programmed polynomial coefficients.
9. The timing signal generator of claim 4 wherein the timing signal generator comprises a first die and a second die, wherein the MEMS resonator is on the first die, wherein the circuitry to control the frequency of operation and the locked-loop circuitry are on the second die, and wherein the first die comprises a pin which is to receive the bias voltage as an input to the first die.
10. The timing signal generator of claim 1 wherein the locked-loop circuitry comprises a divider in a feedback path provided by the locked-loop circuitry and wherein the locked-loop circuitry is to control the divider as a function of the second one of the analog temperature-dependent signal and the digital temperature-dependent signal.
11. The timing signal generator of claim 10 wherein the divider is a fractional divider and wherein the second one is the digital temperature-dependent signal.
12. The timing signal generator of claim 10 wherein the second one is the analog temperature-dependent signal.
13. The timing signal generator of claim 1 wherein the locked-loop circuitry comprises a gain element and wherein the locked-loop circuitry is to control an amount of gain generated by the gain element as a function of the second one of the analog temperature-dependent signal and the digital temperature-dependent signal.
14. The timing signal generator of claim 1 wherein the circuitry to control the frequency of operation comprises a varactor diode and wherein the circuitry to control the frequency of operation is to control the varactor diode using the first one of the analog temperature-dependent signal and the digital temperature-dependent signal.
15. The timing signal generator of claim 1 wherein the temperature sensing circuitry comprises an analog-to-digital converter, and wherein temperature sensing circuitry is to generate the digital temperature-dependent signal from an analog signal.
16. The timing signal generator of claim 1 wherein the locked-loop circuitry comprises a phase-locked loop that is to be controlled using the second one of the analog temperature-dependent signal and the digital temperature-dependent signal.
17. The timing signal generator of claim 1 wherein the locked-loop circuitry comprises a delay-locked loop that is to be controlled using the second one of the analog temperature-dependent signal and the digital temperature-dependent signal.
18. A timing signal generator comprising:
a microelectromechanical systems (MEMS) resonator, wherein the MEMS resonator is to vibrate at a resonant frequency having a temperature dependent variation;
temperature sensing circuitry, including at least one temperature sensor, the temperature sensing circuitry to generate each of an analog temperature-dependent signal and a digital temperature-dependent signal;
bias voltage circuitry, to control a bias voltage supplied to the MEMS resonator as a function of sensed temperature, and thereby control a frequency of operation of the MEMS resonator, using a first one of the analog temperature-dependent signal and the digital temperature-dependent signal; and
locked-loop circuitry to receive a signal representing a resonance frequency of the MEMS resonator and to control generation a timing signal therefrom, for output by the timing signal generator, wherein the locked-loop circuitry comprises at least one of a gain element, an integer divider, a fractional divider, or a variably controlled delay line, which is controlled using a second one of the analog temperature-dependent signal and the digital temperature-dependent signal.
19. The timing signal generator of claim 18 wherein the first one is the digital temperature-dependent signal.
20. The timing signal generator of claim 18 wherein the first one is the analog temperature-dependent signal.