Allegro Microsystems, LLC

Other

Teri L Tu

Ravi Vig

Jay M Towne

Kristann L Moody

P Karl Scheller

Paul W Latham, Ii

Alberto Bilotti

Raymond W Engel

Terry R Clapp

Peter J Gilbert

A magnetic-field-to-voltage transducer includes a Hall element and a digitally gain-controlled Hall-voltage amplifier that produces an analog voltage Vsig having excursions of one polarity corresponding to the passing of magnetic articles. Vsig is applied to the input of a peak-referenced-threshold signal detector that generates a binary proximity-detector output voltage, Vout, having transitions of one direction upon approaches of gear teeth down to zero speed. A digitally gain-controlled amplifier is connected to the Hall element. A comparator circuit generates a binary signal Vbig (or V,) that changes from one to another binary level each time that Vsig exceeds a DC target voltage, V,. The AGC circuit incrementally changes the transducer gain in the direction to bring the peaks in Vsig to just below the target value T,. Reference voltages V,and V,are generated that are equal respectively to the most recent peak positive and negative going excursion in Vsig. DC off-set-limit voltages V,and V,are provided that are respectively above and below the center of the dynamic voltage range of the detector, and the entire signal Vsig at the output of the amplifier is biased in a negative direction when the median value, Vos, of Vsig is greater than V,and moving the entire signal Vsig in a less positive direction when Vos is less than V,to keep Vos within the range from V,to V,.

Centering a signal within the dynamic range of a peak detecting proximity detector

A detector for detecting passing magnetic articles including a magnetic-field-to-voltage transducer having an output at which an analog voltage Vsig is generated, with the Vsig voltage being commensurate to the strength of the ambient magnetic field and having at least one peak. An analog-to-digital converter coupled to the output of the transducer is operative to convert to a corresponding digital signal at least a portion of the Vsig voltage, which portion includes the peak and a circuit coupled to the analog-to-digital converter is operative to generate an output signal indicative of the occurrence of the times t.sub.xpk when the difference between Vsig and said peak of Vsig has exceeded a predetermined amount.

Detection of passing magnetic articles with a peak referenced threshold

A Hall-effect sensor is presented which is adapted to sense a ferromagnetic object, including an integrated circuit chip having a planar Hall element which is positioned in, parallel to, and defines a sensor plane having a front side and a back side, and which element is normal to and centered on a sensor axis, and a magnet structure having an N pole and an S pole, the magnet structure being positioned behind the sensor plane and positioned so that an S pole and an N pole are adjacent each other and both are adjacent the element.

Hall-effect ferromagnetic-article-proximity sensor

In a proximity-detector, a Hall transducer produces a signal Vsig. Two counters, P-counter and N-counter count pulses from a clock and produce count signals respectively to two DACs, PDAC and NDAC. The DACs output signals track and hold, respectively, the positive pulses and negative pulses in Vsig. These output signals are compared with Vsig to produce a proximity-detector binary output voltage Vout that becomes high when a tracking voltage V.sub.DAC-P produced by PDAC rises to each peak positive voltage V.sub.pk in Vsig, and that becomes low when a tracking voltage V.sub.DAC-P falls to each peak negative voltage in Vsig. The peak V.sub.DAC-P is held until Vsig drops by a fixed amount below V.sub.pk to produce an output pulse that resets the counter connected to PDAC at a time shortly following the actual peak in Vsig. Similarly, the peak V.sub.DAC-N is held until Vsig rises a fixed amount above V.sub.DAC-N to produce an output pulse that resets the counter connected to NDAC. The N-counter is reset at t.sub.npk by the negative-peak indicating signal V.sub.Ncomp and is enabled at t.sub.ppk by the positive-peak indicating signal V.sub.Pcomp, while the P-counter reset by the positive peak indicating signal V.sub.Pcomp and enabled by V.sub.Ncomp. This proximity detector detects articles passing at rates down to zero.

Tracking and holding in a DAC the peaks in the field-proportional

A magnetic-field-to-voltage transducer includes a Hall element and a digitally gain-controlled Hall-voltage amplifier that produces an analog voltage Vsig having excursions of one polarity corresponding to the passing of magnetic articles. Vsig is applied to the input of a signal-manipulating circuit that generates a proximity- detector binary output voltage, Vout, having transitions of one direction each time a predetermined point is reached in Vsig. A digitally gain-controlled gain amplifier is connected to the Hall element. A comparator circuit generates a binary signal Vbig (or V.sub.toobig) that changes from one to another binary level each time that Vsig exceeds a DC target voltage, V.sub.TG. The AGC circuit senses and counts gain counter excursions of one polarity in Vsig, and produces a binary count output signal at the input of the gain amplifier at each of the counted excursions in Vsig, incrementally changing the transducer gain in the direction to bring the peaks in Vsig to just below the target value T.sub.TG. This AGC feature prevents saturating the amplifier and quickly renders a Vsig of essentially constant amplitude so that either the peak excursion values or predetermined threshold levels in Vsig, at which transitions in the proximity detector output voltage Vout are caused to occur, provide greater accuracy and stability in the correlation between detection-approach and -withdrawal distances and transitions in Vout.

Detector of passing magnetic articles with automatic gain control

A two-terminal integrated circuit magnetic-field detector, for use in detecting a low level of a liquid in a vehicle, has a Hall element, a Schmitt type comparator, an anti-sloshing accumulator such as an up-down counter, and a latching driver all connected in tandem. The anti-sloshing accumulator is for producing a signal that is the integral as a function of time of the binary comparator output signal. During sloshing, when the average liquid level is near that at which a low-level warning signal is desired, the accumulator signal climbs in a vacillating manner. The latching driver is connected across the two integrated circuit (I.C.) terminals and latches on when the accumulator signal reaches a predetermined value, dropping the impedance across the two I.C terminals. A liquid level indicating lamp is connected in series with a source of DC voltage and the two I.C. terminals, so that when the average position of the floating magnet approaches that of the I.C. detector, the driver latches on and the low-level indicating lamp is also turned on and cannot be turned off except by removing the DC energizing voltage. The accumulator may be an up-down counter with means for preventing counting in the over-flow mode, and also for preventing counting in an under-flow mode, namely downward counting below zero count.

Two terminal I.C. magnetic-field detector for use in a liquid level

A Hall transducer produces a signal Vsig. Threshold voltages V.sub.Pth and V.sub.Nth are generated at the beginning, t.sub.update, of each of a succession of update time intervals, of 64 pulses in Vsig, to be fixed percentages respectively of the peak to peak voltage in Vsig. A proximity-detector binary output voltage is high when Vsig exceeds threshold voltage V.sub.Pth and low when Vsig is below threshold voltage V.sub.Nth. Signals V.sub.Pold and V.sub.Nold, generated by first and second DACs, are equal to the first positive and negative peaks in Vsig after each time t.sub.update initiating the start of a successive interval. Signals V.sub.Pnew and V.sub.Nnew, simultaneously generated by third and fourth DACs, are equal to the greatest positive and negative peak voltages in Vsig during the interval ending at t.sub.update. Counters present their count to the first and second DACs that count pulses from a clock for tracking and holding +/- peaks in Vsig. After each time t.sub.update, a pulse in a signal Vupdt is generated if at time t.sub.update V.sub.Nnew lies outside the range. V.sub.Nold -v to V.sub.Nold +v of if V.sub.Nnew lies outside the range V.sub.Nold -v to V.sub.Nold +v, where v is an incremental DC bias voltage. Vupdt resets the counters so that during the succeeding update time interval the threshold voltages V.sub.Pth and V.sub.Nth have the fixed percentages of the updated threshold voltages V.sub.Pnew -V.sub.Nnew.

Detection of passing magnetic articles while periodically adapting

A low power magnetic-field detector, of the kind for detecting an ambient magnetic field that is greater than a predetermined field strength, is comprised of a Hail element, a transducer-voltage amplifier, and a zero-crossing comparator, all connected in tandem. A clock and switch are used to chop the energizing current to the Hall element. Alternatively, the amplifier and comparator are also chopped to further reduce power consumption. A clockable flip flop is synchronously enabled for an instant at the end of each period of energizing the Hall element. The comparator output signal is transferred to the flip flop Q output and held there during each period of not energizing the Hall element. A Positive-feedback hysteresis circuit adds a bias voltage to the amplified Hall voltage and is applied to the comparator input to effect comparator hysteresis with memory covering clock-period portions when the Hall element is not energized. The comparator is thus transformed into a Schmitt trigger circuit having hysteresis memory, making it possible to chop the Hall element to substantially reduce the detector power consumption without loosing the hysteresis feature.

Chopped low power magnetic-field detector with hysteresis memory

This invention is a magnetic-field sensor assembly comprising a preformed housing shell having a first end which includes an opening, and a second end which includes a window and having a cylindrical shape with a flattened portion to produce a truncated circular cross-section, a sensor package including an integrated-circuit magnetic-field-sensor chip encapsulated in a protective body with first and second opposite and mutually parallel faces and a plurality of integral conductive leads, each lead having a proximal portion, a distal portion, and a central portion, the proximal portion of each of said plurality of leads extending from said body, the central portion of said plurality of leads extending away from the body and positioned substantially normal the faces of the body, said sensor-package body being positioned in said housing shell part way through said window with said one body face extending outwardly from said housing shell and with said lead distal portions extending from said housing shell through said opening, a magnet having a first end and a second end and positioned in said housing shell with said first end adjacent to said second sensor-package body face, and an endcap adapted to close said opening in said housing shell.

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Bow, NH, United States of America

Teri L Tu