# US 8,542,011 B2 · Apparatus and method for reducing a transient signal in a magnetic field sensor > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,542,011 B2 - Document ID: US8542011B2 - Status: Granted - Kind: B2 - Application number: 13/855,279 - Filed: 2013-04-02 - Published: 2013-08-22 - Granted: 2013-09-24 - Earliest claimed: 2010-10-08 - Assignees: Allegro MicroSystems, LLC - Applicants: Allegro Microsystems, LLC - Inventors: Weihua Chen; Michael G. Ward - Web page: https://patentgrep.com/patent/US8542011B2 ## CPC - G01R 33/07: Hall effect devices - G01R 33/0029: {Treating the measured signals, e.g. removing offset or noise} - G01R 33/09: Magnetoresistive devices - H10D 48/40: Devices controlled by magnetic fields - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) - H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES ## Abstract A magnetic field sensor includes a compensation loop coupled in series with normal circuit couplings in order to reduce a transient signal that would otherwise be generated when the magnetic field sensor experiences a high rate of change of magnetic field. In some embodiments, the magnetic field sensor is a current sensor responsive to a magnetic field generated by a current-carrying conductor. ## Claims ### Claim 1 A magnetic field sensor, comprising: a lead frame comprising: a base plate, a ground pin coupled to the base plate, and a signal output pin; a circuit die disposed upon the base plate, the circuit die comprising one or more circuit conductive traces coupled in series between the ground pin and the signal output pin; a circuit loop comprising a conductive path between the ground pin and the signal output pin, wherein the conductive path comprises the one or more circuit conductive traces, wherein the circuit loop has a circuit loop interior area; a compensated signal output node coupled to the signal output pin; and a conductive structure, comprising: a compensation loop coupled in a series arrangement with the circuit loop, wherein the compensation loop has a compensation loop interior area, wherein the compensation loop interior area is selected to be related to the interior area of the circuit loop, wherein a path traversing the circuit loop in a direction from a first end of the series arrangement to a second end of the series arrangement has a circuit loop rotation direction opposite from a compensation loop rotation direction traversing the compensation loop along the same path, and wherein the compensation loop interior area and the compensation loop rotation direction are selected to result in a reduction of an overshoot or an undershoot of an output signal at the compensated signal output node resulting from the circuit loop experiencing a rapid change in flux of the magnetic field. ### Claim 2 (depends on 1) The magnetic field sensor of claim 1, further comprising a circuit board within the magnetic field sensor, the circuit board disposed over the lead frame and proximate to the circuit die, the circuit board comprising a conductive trace disposed thereon, wherein the compensation loop comprises the conductive trace disposed upon the circuit board. ### Claim 3 (depends on 1) The magnetic field sensor of claim 1, wherein the compensation loop interior area is selected to be approximately the same as the interior area of the circuit loop. ### Claim 4 (depends on 1) The magnetic field sensor of claim 1, wherein the compensation loop comprises a conductive trace formed in one or more metal layers of the circuit die, and wherein the compensated signal output node corresponds to the signal output pin. ### Claim 5 (depends on 4) The magnetic field sensor of claim 4, wherein the conductive structure further comprises a wire bond coupled between the circuit die and the signal output pin. ### Claim 6 (depends on 4) The magnetic field sensor of claim 4, wherein the conductive structure further comprises a selected one of a solder ball, a copper pillar, a gold bump, a eutectic and high lead solder bump, a no-lead solder bump, a gold stud bump, a polymeric conductive bump, an anisotropic conductive paste, or a conductive film coupled between the circuit die and the signal output pin. ### Claim 7 (depends on 1) The magnetic field sensor of claim 1, wherein the compensation loop is comprised of a portion of the lead frame, and wherein the compensated signal output node corresponds to the signal output pin. ### Claim 8 (depends on 1) The magnetic field sensor of claim 1, further comprising a circuit board, wherein the compensation loop comprises a conductive trace formed on the circuit board. ### Claim 9 (depends on 8) The magnetic field sensor of claim 8, wherein the circuit board is disposed such that a major surface of the circuit board is proximate to a major surface of the circuit die. ### Claim 10 (depends on 8) The magnetic field sensor of claim 8, wherein circuit board comprises a current-carrying conductive trace configured to carry a current, wherein the magnetic field is generated in response to the current. ### Claim 11 (depends on 1) The magnetic field sensor of claim 1, wherein the circuit die further comprises an amplifier disposed thereon, wherein the circuit loop further comprises a conductive path through the amplifier. ### Claim 12 (depends on 1) The magnetic field sensor of claim 1, further comprising a flux concentrator disposed proximate to the circuit die. ### Claim 13 (depends on 12) The magnetic field sensor of claim 12, wherein the flux concentrator comprises a donut shape having a notch in which the circuit die is disposed. ### Claim 14 (depends on 13) The magnetic field sensor of claim 13, wherein the donut shape has in internal diameter selected to accept a current-carrying conductor configured to carry a current, wherein the magnetic field is generated in response to the current. ### Claim 15 (depends on 1) The magnetic field sensor of claim 1, further comprising a current-carrying conductor configured to carry a current, wherein the magnetic field is generated in response to the current. ### Claim 16 (depends on 15) The magnetic field sensor of claim 15, further comprising a flux concentrator disposed proximate to the circuit die and proximate to the current-carrying conductor. ### Claim 17 (depends on 15) The magnetic field sensor of claim 15, further comprising a U-shaped flux concentrator comprising two legs and an end region joining the two legs, wherein the circuit die and the current-carrying conductor are disposed between the two legs of the U-shaped flux concentrator. ### Claim 18 (depends on 17) The magnetic field sensor of claim 17, further comprising a molded package surrounding the circuit die, wherein the current-carrying conductor comprises first and second major surface and first and second opposing joining surfaces at edges between the first and second major surfaces, wherein the current-carrying conductor comprises a first notch in the first joining surface and a second notch in the second joining surface, wherein the molded package is disposed in a close fit arrangement within the first notch providing relative alignment of the circuit die to the current-carrying conductor, and wherein the end region of the U-shaped flux concentrator is disposed within the second notch in a close fit arrangement providing relative alignment of the U-shaped flux concentrator to the current-carrying conductor and to the circuit die. ### Claim 19 A method of compensating an output signal in a magnetic field sensor responsive to a magnetic field, the magnetic field sensor comprising a lead frame having a ground pin and a signal output pin, the magnetic field sensor also comprising a circuit die disposed upon the base plate, the circuit die comprising one or more circuit conductive traces coupled in series between the ground pin and the signal output pin, the method comprising: identifying a circuit loop in the magnetic field sensor comprised of a conductive path between the ground pin and the signal output pin, wherein the conductive path comprises the one or more circuit conductive traces, wherein the circuit loop comprises a circuit loop interior area; providing a compensated signal output node coupled to the signal output pin; and providing a conductive structure, comprising: providing a compensation loop coupled in a series arrangement with the circuit loop, wherein the compensation loop has a compensation loop interior area, wherein the compensation loop interior area is selected to be related to the interior area of the circuit loop, wherein a path traversing the circuit loop in a direction from a first end of the series arrangement to a second end of the series arrangement has a circuit loop rotation direction opposite from a compensation loop rotation direction traversing the compensation loop along the same path, and wherein the compensation loop interior area and the compensation loop rotation direction are selected to result in a reduction of an overshoot or an undershoot of an output signal at the compensated signal output node resulting from the circuit loop experiencing a rapid change in flux of the magnetic field. ### Claim 20 (depends on 19) The method of claim 19, further comprising providing a circuit board within the magnetic field sensor, the circuit board disposed over the lead frame and proximate to the circuit die, the circuit board comprising a conductive trace disposed thereon, wherein the compensation loop comprises the conductive trace disposed upon the circuit board. ### Claim 21 (depends on 19) The method of claim 19, wherein the compensation loop interior area is selected to be approximately the same as the interior area of the circuit loop. ### Claim 22 (depends on 19) The method of claim 19, wherein the compensation loop comprises a conductive trace formed in one or more metal layers of the circuit die, and wherein the compensated signal output node corresponds to the signal output pin. ### Claim 23 (depends on 19) The method of claim 19, wherein the compensation loop is comprised of a portion of the lead frame, and wherein the compensated signal output node corresponds to the signal output pin. ### Claim 24 (depends on 19) The method of claim 19, wherein the compensation loop comprises a conductive trace formed on a circuit board. ### Claim 25 (depends on 24) The method of claim 24, wherein the circuit board is disposed such that a major surface of the circuit board is proximate to a major surface of the circuit die. ### Claim 26 (depends on 24) The method of claim 24, wherein circuit board comprises a current-carrying conductive trace configured to carry a current, wherein the magnetic field is generated in response to the current. ### Claim 27 (depends on 19) The method of claim 19, wherein the circuit die further comprises an amplifier disposed thereon, wherein the circuit loop further comprises a conductive path through the amplifier. ### Claim 28 (depends on 19) The method of claim 19, further comprising placing a flux concentrator proximate to the circuit die. ### Claim 29 (depends on 28) The method of claim 28, wherein the flux concentrator comprises a donut shape having a notch in which the circuit die is disposed. ### Claim 30 (depends on 19) The method of claim 19, wherein the donut shape has in internal diameter selected to accept a current-carrying conductor configured to carry a current, wherein the magnetic field is generated in response to the current. ### Claim 31 (depends on 19) The method of claim 19, further comprising placing a current-coming conductor configured to carry a current proximate to the circuit die, wherein the magnetic field is generated in response to the current. ### Claim 32 (depends on 31) The method of claim 31, further comprising placing a flux concentrator proximate to the circuit die and proximate to the current-carrying conductor. ### Claim 33 (depends on 31) The method claim 31, further comprising placing a U-shaped flux concentrator proximate to the circuit die, the U-Shaped flux concentrator comprising two legs and an end region joining the two legs, wherein the circuit die and the current-carrying conductor are disposed between the two legs of the U-shaped flux concentrator. ### Claim 34 (depends on 33) The method of claim 33, further comprising molding a molded package surrounding the circuit die, wherein the current-carrying conductor comprises first and second major surface and first and second opposing joining surfaces at edges between the first and second major surfaces, wherein the current-carrying conductor comprises a first notch in the first joining surface and a second notch in the second joining surface, wherein the molded package is disposed in a close fit arrangement within the first notch providing relative alignment of the circuit die to the current-carrying conductor, and wherein the end region of the U-shaped flux concentrator is disposed within the second notch in a close fit arrangement providing relative alignment of the U-shaped flux concentrator to the current-carrying conductor and to the circuit die.