LOW-POWER SYSTEM CLOCK CALIBRATION BASED ON A HIGH- ACCURACY REFERENCE CLOCK
First Claim
1. An implantable medical device (IMD) comprising:
- a processor;
a system clock that comprises a low power oscillator, according to which the processor operates the IMD;
a reference clock that comprises a high accuracy oscillator; and
a clock calibrator that periodically performs a calibration routine to calibrate the system clock based on the reference clock, wherein the system clock is continuously powered and the reference clock is powered during the calibration routine.
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Abstract
Various techniques are described for periodically performing a calibration routine to calibrate a low-power system clock within an implantable medical device (IMD) based on a high accuracy reference clock also included in the IMD. The system clock is powered continuously, and the reference clock is only powered on during the calibration routine. The techniques include determining a clock error of the system clock based on a difference between frequencies of the system clock and the reference clock over a fixed number of clock cycles, and adjusting a trim value of the system clock to compensate for the clock error. Calibrating the system clock with a delta-sigma loop, for example, reduces the clock error over time. This allows accurate adjustment of the system clock to compensate for errors due to trim resolution, circuit noise and temperature.
130 Citations
36 Claims
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1. An implantable medical device (IMD) comprising:
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a processor; a system clock that comprises a low power oscillator, according to which the processor operates the IMD; a reference clock that comprises a high accuracy oscillator; and a clock calibrator that periodically performs a calibration routine to calibrate the system clock based on the reference clock, wherein the system clock is continuously powered and the reference clock is powered during the calibration routine. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method comprising:
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operating an implantable medical device (IMD) in accordance with a system clock that comprises a low power oscillator clock included in the IMD; and periodically performing a calibration routine to calibrate the system clock based on the reference clock, wherein the system clock is continuously powered and the reference clock is powered during the calibration routine. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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19. An implantable medical device (IMD) comprising:
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a system clock that comprises a low power oscillator; a reference clock that comprises a high accuracy oscillator; means for operating the IMD in accordance with the system clock; and means for periodically performing a calibration routine to calibrate the system clock based on the reference clock, wherein the system clock is continuously powered and the reference clock is powered during the calibration routine. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27)
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28. A computer-readable storage medium comprising instructions that, when executed, cause a programmable processor to:
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operate an implantable medical device (IMD) in accordance with a system clock that comprises a low power oscillator clock included in the IMD; and periodically perform a calibration routine to calibrate the system clock based on the reference clock, wherein the system clock is continuously powered and the reference clock is powered during the calibration routine. - View Dependent Claims (29, 30, 31, 32, 33, 34, 35, 36)
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Specification