Low-power system clock calibration based on a high-accuracy reference clock

摘要

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.

主权项

1. A method comprising:
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, wherein the reference clock comprises a crystal oscillator.