US 8,749,313 B2 · Correction of low accuracy clock

Abstract

An electronic device has two oscillators, for example a first highly accurate crystal oscillator and a second less accurate low power oscillator. In a normal mode of operation, time is counted based on an output from the crystal oscillator, but in a low power mode of operation, time is counted based on an output from the less accurate oscillator. During the low power mode of operation, a calibration process is performed repeatedly. During a first calibration time period the second oscillator is calibrated against the first oscillator to obtain a first calibration result, and a recalibration is performed during a second calibration time period to obtain a second calibration result. A correction factor is determined from the first and second calibration results, and the correction factor is applied when subsequently counting time based on the output from the second oscillator.

Claims30

Dependent claims

A method of operation of an electronic device, having a first oscillator and a second oscillator, the method comprising:

in a normal mode of operation, counting time based on an output from the first oscillator;
and
in a low power mode of operation, counting time based on an output from the second oscillator;
and further comprising, in the low power mode of operation, repeatedly:
calibrating the second oscillator against the first oscillator during a first calibration time period to obtain a first calibration result,
recalibrating the second oscillator against the first oscillator during a second calibration time period to obtain a second calibration result,
determining a correction factor from the first and second calibration results, and
subsequently applying the correction factor when counting time based on the output from the second oscillator.

5 more elements

A method of operation of an electronic device having a first oscillator and a second oscillator, the method comprising:

switching, at a beginning of a first calibration time period, the first oscillator on and calibrating the second oscillator against the first oscillator during the first calibration time period to obtain a first calibration result representing a first frequency of the second oscillator during the first calibration time period;
and subsequently
switching, at an end of the first calibration time period, the first oscillator off;
and subsequently
counting oscillations from the second oscillator, until a first count is reached;
and subsequently
switching, at a beginning of a second calibration time period, the first oscillator on and calibrating the second oscillator against the first oscillator during the second calibration time period to obtain a second calibration result representing a second frequency of the second oscillator during the second calibration time period;
and
switching, at an end of the second calibration time period, the first oscillator off;
and
providing a time parameter presenting a future point in time and, based on the first and second calibration results and on the first count of oscillations, estimating a second count of oscillations of the second oscillator to count after the end of the second calibration period in order to reach said future point in time;
counting oscillations from the second oscillator, until the second count is reached, and then initiating a first action.

9 more elements

A method of operation of an electronic device having a first oscillator and a second oscillator, the method comprising:

switching, if in a switched off state, at a beginning of a first calibration time period, the first oscillator on and calibrating the second oscillator against the first oscillator during the first calibration time period to obtain a first calibration result representing a first frequency of the second oscillator during the first calibration time period;
and subsequently
switching, at an end of the first calibration time period, the first oscillator off;
and subsequently
counting oscillations from the second oscillator, until a first count is reached;
and subsequently
switching, at a beginning of a second calibration time period, the first oscillator on and calibrating the second oscillator against the first oscillator during the second calibration time period to obtain a second calibration result representing a second frequency of the second oscillator during the second calibration time period;
and
switching, at an end of the second calibration time period, the first oscillator off;
and switching, at a beginning of a third calibration time period, the first oscillator on and calibrating the second oscillator against the first oscillator during the third calibration time period to obtain a third calibration result representing a third frequency of the second oscillator during the third calibration time period;
and subsequently
switching, at an end of the third calibration time period, the first oscillator off;
and
determining, based on difference between the third calibration result and an expected third calibration result derived from the first and second calibration results, a length of a first time to wait until a further calibration time period.

11 more elements

A method of determining a degree of temperature stability of an electronic device having a first oscillator and a second oscillator, the method comprising:

switching, if in a switched off state, at a beginning of a first calibration time period, the first oscillator on and calibrating the second oscillator against the first oscillator during the first calibration time period to obtain a first calibration result representing a first frequency of the second oscillator during the first calibration time period;
and subsequently
switching, at an end of the first calibration time period, the first oscillator off;
and subsequently
counting oscillations from the second oscillator, until a first count is reached;
and subsequently
switching, at a beginning of a second calibration time period, the first oscillator on and calibrating the second oscillator against the first oscillator during the second calibration time period to obtain a second calibration result representing a second frequency of the second oscillator during the second calibration time period;
and
switching, at an end of the second calibration time period, the first oscillator off;
and
switching, at a beginning of a third calibration time period, the first oscillator on and calibrating the second oscillator against the first oscillator during the third calibration time period to obtain a third calibration result representing a third frequency of the second oscillator during the third calibration time period;
and subsequently
switching, at an end of the third calibration time period, the first oscillator off;
and
determining the degree of temperature stability by comparing the first, second and third calibration results.

12 more elements

Dependencies are inferred from the claim text.

Correction of low accuracy clock

Life of this patent

Correction of low accuracy clock

Life of this patent

Abstract

Claims30