Sprague Electric Company

Allegro Microsystems, LLC

Jacob K Higgs

Ravi Vig

Grant D Avery

Hideki Kawaji

John Humenick

Barbara L Gibson

There is added to a conventional magnetic-field detector, which includes a magnetic-field-to-voltage transducer such as a Hall element connected to a Schmitt trigger circuit, a DC voltage monitor circuit to produce a high binary monitor signal only when the DC supply voltage is within a predetermined normal band, and a logic circuit having one input connected to the output of the monitor circuit and a second input connected to the output of the Schmitt trigger circuit. During periods when the binary-Schmitt-output voltage remains high, corresponding for example to a high ambient magnetic field, noise spikes on the DC line can cause an anomalous change in the binary-Schmitt-output voltage of a magnetic-field detector from a high level to a low level. The logic circuit is such that during an enabling period in which the output signal from the DC supply voltage monitor is continuously of the one type, the logic output produces a binary logic output-signal transition from a first binary level to the second binary level only following a transition in the Schmitt output signal from the high level to the low level, so that in the presence of noise spikes of either polarity that momentarily cause the DC supply voltage to exit the predetermined normal DC supply voltage band, the binary logic output signal essentially mirrors the Schmitt output signal with noise removed.

Magnetic field detector with noise blanking

A proximity detector includes a magnet having steel or iron pole piece plates mounted at front and rear pole ends of the magnet, and a silicon integrated circuit mounted to the outer surface of the front pole piece centered about at the magnet pole axis. The integrated circuit includes two essentially identical Hall elements having outputs connected series opposing, i.e. differentially rather than aiding, so that distortion of the magnet field ambient to the integrated circuit caused by a ferromagnetic article passing by results in a gradient field between the Hall elements producing a differential output signal. The dual Hall element integrated circuit leads to a low differential composite offset voltage while the front pole piece renders the magnetic flux density much more uniform further reducing this dual-Hall-element composite offset voltage.

Proximity selectro with integral magnet, pole-piece plate and pair of

An integrated circuit switch including a Hall element, a Hall-voltage amplifier having an output to which the inputs of two Schmitt trigger circuits are connected may be mounted between stator windings in a brushless D.C. motor as a rotor position detector and motor commutator circuit. The outputs of the respective Schmitt trigger circuit may be connected to excite a pair of the stator windings. The two binary exciting signals are mutually complimentary except for having non-simultaneous changes from one binary state to the other. Integrated circuits of this invention eliminate acoustic noise that is caused by such overlapping stator currents that were unwittingly present in commutation circuits of the prior art.

Dual trigger Hall effect I.C. switch

An integrated circuit voltage regulator is of the kind having a pass transistor connected collector-to-emitter between the input V.sub.CC conductor and the regulated-voltage output conductor, a current source circuit supplying a base bias current to the pass transistor and a voltage reference and feedback regulator circuit connected between the output voltage conductor and the base of the pass transistor. A protective circuit against high voltage transients adding to V.sub.CC voltage comprises a transistor connected collector-to-emitter between the pass-transistor base and ground has a resistor paralleling the base-emitter junction, which resistor is resistively coupled to the input V.sub.CC line to shunt away the pass-transistor bias current whenever the V.sub.CC voltage level exceeds a value just under the latch-back breakdown voltage of the pass transistor. A zener diode directly connected across the DC input voltage conduction renders the regulator even more tolerant of high voltage transients.

Integrated voltage regulator circuit with transient voltage protection

An integrated circuit includes an epitaxial layer. In a near central region thereof is formed a symmetrical array of four equal sized Hall cells that are connected in parallel to form one Hall element. A moat surrounds the Hall element consisting of two concentric isolation walls separated by a band of opposite conductivity epitaxial material. The output of the Hall element is connected to the input of an adjacent differential amplifier that has two extraordinarily large amplifying transistors with emitter areas each equal to about a half of a Hall area, for achieving much better control over the relative dimensions of these emitters and thus over the amplifier offset voltage from chip to chip. The emitter resistors are likewise made very wide and both pairs of components are physically arranged to have balanced thermal coupling to the Hall element for further enhancing control of offset voltage.

Integrated Hall element and amplifier with controlled offset voltage

A silicon integrated circuit has a Hall-element, a differential amplifier and a Schmitt trigger circuit connected in tandem to form a Hall switch. It is demonstrated that only one set of component parameters, e.g. resistor values, exists that provides an optimally smooth temperature coefficient (TC) of Hall-switch operate-point. It is further shown that by adding an adjustable resistor from the Schmitt trigger circuit ground, which resistor has the same resistivity and TC as does the Hall element, adjustment of the operate-point to another particular operate-point is accomplished without substantially altering the above-noted optimum TC. Operate-point adjustment, e.g. by blowing fuse links, during manufacturing, at probe, can be effected to yield a narrow distribution of operate-points conforming to a customer specification.

Integrated circuit hall switch with adjustable operate point

A silicon integrated circuit includes a centrally located Hall element having an annular moat region surrounding the Hall element to isolate it from built in stresses in adjacent parts of the integrated circuit. The moat comprises at least one annular isolation wall, but preferably two concentric isolation walls. This moat construction also leads to a reduction in dependency of Hall element symmetry upon process variables.

Integrated circuit with stress isolated Hall element

A strong magnet is bonded to a conventional Hall element package. A bias current is introduced at one of the output terminals of the Hall element in the direction to cause a reduction in the magnet-bias-induced output voltage. This output voltage is easily reduced by this means to zero. The resulting Hall-element detector is shrouded by a large magnetic biasing field while presenting a low or zero DC output component upon which the signal voltage will be superimposed.

Hall element with bucking current and magnet biases

An integrated circuit including a Hall element and a threshold detector is encased in a plastic housing with the plane of the Hall element parallel with a face of the housing, providing a two-state Hall element proximity sensor. A light emitting diode (L.E.D.) is mounted in the housing and is connected to the output of the detector, providing visual indication of the state of the sensor. A kit includes the sensor and a compatible magnet to provide to users of little skill, proximity sensor parts that are easily assembled and made immediately effective in use.

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Salisbury, NH, United States of America

Jacob K Higgs