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US 6,356,741 B1Granted
Magnetic pole insensitive switch circuit
AssigneeAllegro MicroSystems, LLC
InventorsAlberto Bilotti, Glenn A. Forrest, Ravi Vig
Life of this patent
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Abstract
A switch which is magnetic pole insensitive is described. The switch includes a Hall effect sensor coupled to a threshold circuit which provides an output signal indicative of the proximity of a magnet, and hence a magnetic field, to the Hall effect sensor regardless of the orientation of the magnet to the Hall effect sensor.
Claims26
A circuit comprising:
- a sensor having at least one output port at which a first signal voltage is provided in response to the presence of a magnetic field of a first polarity and at which a second signal voltage is provided in response to the presence of magnetic field of a second polarity;
- and
- a detector having at least one input port coupled to the at least one output port of the sensor and an output port at which an output signal is provided, the output signal being indicative of the presence of said magnetic field of said first polarity and the presence of said magnetic field of said second polarity, said detector comprising a first circuit for comparing said first signal voltage to a first threshold level and a second circuit for comparing said second signal voltage to a second threshold level, wherein said first and second threshold levels are adjustable with a common adjustment mechanism.
In a wireless communication device, a switching system for providing a signal in response to an article which provides a magnetic field, the switching system comprising:
- (a) a sensor for sensing the magnetic field of the magnetic article, said sensor for generating a first signal voltage having a signal voltage level which is proportional to a magnetic field having a first polarity and a second signal voltage having a signal voltage level that is proportional to a magnetic field having a second different polarity;
- and
- (b) a threshold detection circuit coupled to the sensor to receive the first and second signal voltages and responsive to a supply voltage to provide an output signal having a first value when said magnetic article is within a predetermined distance of the sensor regardless of the polarity of the magnetic field, said threshold detection circuit comprising a first circuit for comparing said first signal voltage to a first threshold level and a second circuit for comparing said second signal voltage to a second threshold level, wherein said first and second threshold levels are substantially constant in response to variations in said supply voltage.
A switching system for providing a signal in response to an article which provides a magnetic field, the switching system comprising:
- (a) a sensor for sensing the magnetic field of the magnetic article, said sensor for generating a first signal voltage having a signal voltage level which is proportional to a magnetic field having a first polarity and a second signal voltage having a signal voltage level that is proportional to a magnetic field having a second different polarity, wherein said sensor is a Hall element circuit;
- (b) a threshold detection circuit coupled to the Hall element circuit to receive the first and second signal voltages and responsive to a supply voltage to provide an output signal having a first value when said magnetic article is within a predetermined distance of the sensor regardless of the polarity of the magnetic field with respect to said Hall element circuit, said threshold detection circuit comprising a first circuit for comparing said first signal voltage to a first threshold level and a second circuit for comparing said second signal voltage to a second threshold level, wherein said first and second threshold levels are substantially constant in response to variations in said supply voltage, wherein said threshold detection circuit is a window comparator comprising first and second differential pair circuits, each having an input terminal coupled to one of a pair of outputs from said Hall element circuit and an output terminal coupled to an output terminal of said comparator;
- and
- (c) a filter and level shifter circuit coupled between said Hall element circuit and said comparator.
1 more element
A switching system for providing a signal in response to an article which provides a magnetic field, the switching system comprising:
- (a) a sensor for sensing the magnetic field of the magnetic article, said sensor for generating a first signal voltage having a signal voltage level which is proportional to a magnetic field having a first polarity and a second signal voltage having a signal voltage level that is proportional to a magnetic field having a second different polarity, wherein said sensor is a Hall element circuit;
- (b) a threshold detection circuit coupled to the Hall element circuit to receive the first and second signal voltages and responsive to a supply voltage to provide an output signal having a first value when said magnetic article is within a predetermined distance of the sensor regardless of the polarity of the magnetic field with respect to said Hall element circuit, said threshold detection circuit comprising a first circuit for comparing said first signal voltage to a first threshold level and a second circuit for comparing said second signal voltage to a second threshold level, wherein said first and second threshold levels are substantially constant in response to variations in said supply voltage, wherein said threshold detection circuit is a window comparator comprising it and second differential pair circuits, each having an input terminal coupled to one of a pair of outputs from said Hall element circuit and an output terminal coupled to an output terminal of said comparator;
- (c) first and second output amplifier stages, each of the output amplifier stages coupled between a respective one of the output terminals of the first and second differential pair circuits and the output terminal of said comparator;
- and
- (d) an output/buffer amplifier stage having an in put terminal coupled to the output terminal of each of said first and second output amplifier stages and having an output terminal coupled to the output terminal of said comparator.
2 more elements
A cellular telephone comprising:
- a base;
- a cover having a first end movably coupled to said base and a second end;
- a magnetic article disposed in the second end of said cover, said magnetic article having a first pole and a second pole;
- and
- a switch disposed in said base, said switch comprising:
- a sensor for sensing the magnetic field of the magnetic article, said sensor for generating a first signal voltage having a signal voltage level which is proportional to a magnetic field having a first polarity and a second opposite signal voltage having an opposite signal voltage level that is proportional to a magnetic field having a second different polarity;
- and
- a comparator coupled to the sensor to receive the first and second signal voltages and to provide an output signal having a first value when said magnetic article is within a predetermined distance of the sensor regardless of the polarity of the magnetic field.
5 more elements
A method of switching in a wireless communication device comprising the steps of:
- (a) sensing with a magnetic field sensing element a magnetic field provided by a magnetic article having a first pole region and a second pole region wherein said magnetic article has first magnetic field polarity at the first pole region and a second different magnetic field polarity at the second pole region;
- (b) generating a sensor output signal having a signal level which is proportional to the magnetic field sensed in step (a), wherein the sensor output signal has a first signal direction when said first pole region is proximate said magnetic field sensing element and a second opposite signal direction when said second pole region is proximate said magnetic field sensing element;
- (c) comprising the sensor output signal to one of first and second threshold signal levels;
- and
- (d) in response to the sensor output signal level reaching or exceeding the one of the first and second threshold signal levels, providing an output signal having a first signal level regardless of the direction of the sensor output signal.
2 more elements
Dependencies are inferred from the claim text.