Low-power activation circuit with magnetic motion sensor
First Claim
1. A circuit, comprising:
- a motion sensor element configured to output a motion sensor output signal corresponding to a detected motion to a digital difference detection circuit;
wherein the digital difference detection circuit comprises;
a digital measurement element configured to track the motion sensor output signal and generate a digital signal;
a digital storage element configured to store one or more previous digital signals corresponding to the motion sensor output signal generated over time; and
a difference detector configured to detect a difference between a current digital signal and the previous digital signals, 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 mode; and
a bi-phase operating element configured to enable the difference detector to operate according to an operating phase during which the difference detector measures the difference, and a low power standby phase during which the difference detector is unpowered.
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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.
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Citations
17 Claims
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1. A circuit, comprising:
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a motion sensor element configured to output a motion sensor output signal corresponding to a detected motion to a digital difference detection circuit; wherein the digital difference detection circuit comprises; a digital measurement element configured to track the motion sensor output signal and generate a digital signal; a digital storage element configured to store one or more previous digital signals corresponding to the motion sensor output signal generated over time; and a difference detector configured to detect a difference between a current digital signal and the previous digital signals, 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 mode; and a bi-phase operating element configured to enable the difference detector to operate according to an operating phase during which the difference detector measures the difference, and a low power standby phase during which the difference detector is unpowered. - View Dependent Claims (2, 3, 4, 5, 6)
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7. An activation circuit, comprising:
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a magnetic motion sensor configured to output a magnetic signal proportional to a measured magnetic field; a digital difference detection circuit, comprising; an analog-to-digital converter configured to receive the magnetic signal and to track the measured magnetic field by converting the magnetic signal to a digital signal which corresponds to the measured magnetic field; a difference detector configured to measure a difference by detecting a continual upward or downward change for a time, wherein if the time of the continual upward or downward change is larger than a digital reference level the difference detection circuit causes an activation signal generator to generate an activation signal that awakens a system from a sleep. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A method for activating a system from a sleep mode, comprising:
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generating a current digital signal proportional to a current magnetic field measured by a magnetic motion sensor; performing offset compensation to remove a non-zero offset present in the current digital signal in an absence of a magnetic field, by calculating a difference between offset values of the magnetic motion sensor, and generating a chopping signal having a modulated amplitude which is based upon the difference between offset values; detecting a difference between a current offset compensated digital signal and a previous offset compensated digital signal proportional to a previous magnetic field previously measured by the magnetic motion sensor and stored in a digital storage element; and comparing the detected difference to a digital reference level, wherein if the difference is larger than the digital reference level an activation signal awakens a system from a sleep mode.
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Specification