Low-power activation circuit with motion sensor
First Claim
1. An activation circuit, comprising:
- a motion sensor configured to output a signal comprising a differential signal proportional to a measured quantity;
a comparator configured to receive the differential signal from the motion sensor and to generate a comparator signal from the differential signal;
a digital logic element coupled to an output of the comparator and configured to generate a digital signal from the comparator signal;
a digital storage element configured to store one or more previous digital signals;
a difference detector, wherein in an operating phase the difference detector is configured to measure a difference between the digital signal from the digital logic element and a previous digital signal from the digital storage element and to output a difference signal comprising information concerning a magnitude of the difference, wherein if the difference is larger than a digital reference level, the difference detector causes an activation signal generator to generate an activation signal that awakens a system from a sleep; and
wherein in a low power standby phase, digital signals are stored in the digital storage element.
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Abstract
One embodiment of the present invention relates to a method and apparatus to perform a low power activation of a system by measuring the slope of a digital signal corresponding to a motion sensor measurement value. In one embodiment, a low power activation circuit is coupled to magnetic motion sensor configured to output a magnetic signal proportional to a measured magnetic field. The low power activation circuit may comprise a digital tracking circuit configured to provide a digital signal that tracks the magnetic field and a difference detector configured to detect a difference between a current digital signal and a prior digital signal stored in a digital storage means. If the detected difference is larger than a digital reference level, an activation signal is output to awaken a system from a sleep mode.
24 Citations
20 Claims
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1. An activation circuit, comprising:
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a motion sensor configured to output a signal comprising a differential signal proportional to a measured quantity; a comparator configured to receive the differential signal from the motion sensor and to generate a comparator signal from the differential signal; a digital logic element coupled to an output of the comparator and configured to generate a digital signal from the comparator signal; a digital storage element configured to store one or more previous digital signals; a difference detector, wherein in an operating phase the difference detector is configured to measure a difference between the digital signal from the digital logic element and a previous digital signal from the digital storage element and to output a difference signal comprising information concerning a magnitude of the difference, wherein if the difference is larger than a digital reference level, the difference detector causes an activation signal generator to generate an activation signal that awakens a system from a sleep; and wherein in a low power standby phase, digital signals are stored in the digital storage element. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A method for activating a system from a sleep, comprising:
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generating a digital signal proportional to a measured motion sensor signal; performing offset compensation to remove a non-zero offset that is present in the digital signal; detecting a difference between an offset compensated current digital signal and offset compensated previous digital signals, that are stored in a digital storage element; and comparing the detected difference to a digital reference level, wherein if the difference is larger than a digital reference level an activation signal awakens a system from a sleep mode. - View Dependent Claims (15)
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16. An activation circuit, comprising:
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a motion sensor configured to output a signal proportional to a measured quantity; a digital difference detection circuit configured to operate in a low power standby phase and an operating phase, a low power oscillator configured to provide a first plurality of clock signals to an activation signal generator in the low power standby phase; a fast oscillator configured to provide a second plurality of clock signals to the digital difference detection circuit in the operating phase; wherein in the low power standby phase, digital signals are stored in a digital storage element; and wherein in the operating phase the digital difference detection circuit compares a current digital signal to previous digital signals stored in the digital storage element, and causes the activation signal generator to generate an activation signal that awakens a system from a sleep if a difference between the current digital signal and the previous digital signals is larger than a non-zero digital reference level. - View Dependent Claims (17, 18, 19, 20)
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Specification