# US 11,029,373 B2 · Magnetic field sensors having a magnetic anti-aliasing filter > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,029,373 B2 - Document ID: US11029373B2 - Status: Granted - Kind: B2 - Application number: 16/512,680 - Filed: 2019-07-16 - Published: 2021-01-21 - Granted: 2021-06-08 - Earliest claimed: 2019-07-16 - Assignees: Allegro MicroSystems, LLC - Applicants: Allegro MicroSystems, LLC - Inventors: Alexander Latham; Evan Shorman - Web page: https://patentgrep.com/patent/US11029373B2 ## CPC - G01R 33/0029: {Treating the measured signals, e.g. removing offset or noise} - G01R 33/07: Hall effect devices - G01R 15/207: {Constructional details independent of the type of device used} - G01R 33/007: {Environmental aspects, e.g. temperature variations, radiation, stray fields (G01R33/025 takes precedence)} - G01R 33/0076: {Protection, e.g. with housings against stray fields} - H05K 9/0075: {Magnetic shielding materials} - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) - H05K: PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS ## Abstract A magnetic field sensor includes a substrate, a first channel comprising a first magnetic field sensing element supported by the substrate and configured to generate a first magnetic field signal indicative of a first magnetic field experienced by the first magnetic field sensing element, a second channel comprising a second magnetic field sensing element supported by the substrate and configured to generate a second magnetic field signal indicative of a second magnetic field experienced by the second magnetic field sensing element, and at least one shield configured to reduce a bandwidth of the first magnetic field by a first amount and to reduce a bandwidth of the second magnetic field by a second amount. The shield is able to act as a magnetic anti-aliasing filter for the magnetic field sensing elements, which can then be chopped or sampled. ## Claims ### Claim 1 A magnetic field sensor comprising: a substrate; a first channel comprising a first magnetic field sensing element supported by the substrate and configured to generate a first magnetic field signal indicative of a first magnetic field experienced by the first magnetic field sensing element; a second channel comprising a second magnetic field sensing element supported by the substrate and configured to generate a second magnetic field signal indicative of a second magnetic field experienced by the second magnetic field sensing element; and at least one shield configured to reduce a bandwidth of the first magnetic field by a first amount and to reduce a bandwidth of the second magnetic field by a second amount, wherein the second amount by which the at least one shield reduces the bandwidth of the second magnetic field is approximately zero. ### Claim 2 (depends on 1) The magnetic field sensor of claim 1, wherein the first channel further comprises a switching circuit coupled to receive the first magnetic field signal and configured to generate a sampled signal. ### Claim 3 (depends on 2) The magnetic field sensor of claim 2, wherein the at least one shield is configured to reduce aliasing of the sampled signal. ### Claim 4 (depends on 2) The magnetic field sensor of claim 2, wherein the switching circuit comprises a chopping circuit configured to chop the first magnetic field sensing element. ### Claim 5 (depends on 2) The magnetic field sensor of claim 2, wherein the switching circuit comprises an analog-to-digital converter configured to convert the first magnetic field signal into a digital signal. ### Claim 6 (depends on 1) The magnetic field sensor of claim 1, wherein the first channel is further configured to generate a first sensor output signal based on the first magnetic field signal and the second channel is further configured to generate a second sensor output signal based on the second magnetic field signal. ### Claim 7 (depends on 1) The magnetic field sensor of claim 1, further comprising a processor coupled to receive the first magnetic field signal and the second magnetic field signal and configured to generate a combined sensor output signal based on the first magnetic field signal and the second magnetic field signal. ### Claim 8 (depends on 7) The magnetic field sensor of claim 7, further comprising: a first signal path configured to carry a low frequency signal extracted from the second magnetic field signal from the second channel to the first channel; and a second path configured to carry an offset-compensated signal from the first channel to the second channel to compensate for an offset associated with the second magnetic field signal. ### Claim 9 (depends on 1) The magnetic field sensor of claim 1, wherein the magnetic field sensor comprises a current sensor. ### Claim 10 (depends on 1) The magnetic field sensor of claim 1, wherein the magnetic field sensor comprises a linear sensor. ### Claim 11 (depends on 1) The magnetic field sensor of claim 1, further comprising a lead frame supporting the substrate, wherein the at least one shield comprises a die attach pad of the lead frame that is disposed under the first magnetic field sensing element and is not disposed under the second magnetic field sensing element. ### Claim 12 (depends on 1) The magnetic field sensor of claim 1, wherein the at least one shield comprises a conductive layer disposed over the first magnetic field sensing element and not disposed over the second magnetic field sensing element. ### Claim 13 (depends on 12) The magnetic field sensor of claim 12, wherein the at least one shield is a solid or patterned conductive layer. ### Claim 14 A method comprising: generating a first magnetic field signal indicative of a first magnetic field experienced by a first magnetic field sensing element, the first magnetic field sensing element supported by a substrate; generating a second magnetic field signal indicative of a second magnetic field experienced by a second magnetic field sensing element, the second magnetic field sensing element supported by the substrate; reducing a bandwidth of the first magnetic field by a first amount using at least one shield; and reducing a bandwidth of the second magnetic field by a second amount using the at least one shield, wherein the second amount by which the at least one shield reduces the bandwidth of the second magnetic field signal is approximately zero. ### Claim 15 (depends on 14) The method of claim 14, further comprising generating a sampled signal from the first magnetic field signal and reducing aliasing of the sampled signal. ### Claim 16 (depends on 14) The method of claim 14, further comprising chopping the first magnetic field sensing element. ### Claim 17 A magnetic field sensor comprising: a substrate; a first channel comprising a first magnetic field sensing element supported by the substrate and configured to generate a first magnetic field signal indicative of a first magnetic field experienced by the first magnetic field sensing element, wherein the first channel further comprises a switching circuit coupled to receive the first magnetic field signal and configured to generate a sampled signal; a second channel comprising a second magnetic field sensing element supported by the substrate and configured to generate a second magnetic field signal indicative of a second magnetic field experienced by the second magnetic field sensing element; and at least one shield configured to reduce a bandwidth of the first magnetic field by a first amount and to reduce a bandwidth of the second magnetic field by a second amount, wherein the at least one shield is configured to reduce aliasing of the sampled signal. ### Claim 18 (depends on 17) The magnetic field sensor of claim 17, wherein the first channel is further configured to generate a first sensor output signal based on the first magnetic field signal and the second channel is further configured to generate a second sensor output signal based on the second magnetic field signal. ### Claim 19 (depends on 17) The magnetic field sensor of claim 17, further comprising a processor coupled to receive the first magnetic field signal and the second magnetic field signal and configured to generate a combined sensor output signal based on the first magnetic field signal and the second magnetic field signal. ### Claim 20 (depends on 19) The magnetic field sensor of claim 19, further comprising: a first signal path configured to carry a low frequency signal extracted from the second magnetic field signal from the second channel to the first channel; and a second path configured to carry an offset-compensated signal from the first channel to the second channel to compensate for an offset associated with the second magnetic field signal. ### Claim 21 A magnetic field sensor comprising: a substrate; a first channel comprising a first magnetic field sensing element supported by the substrate and configured to generate a first magnetic field signal indicative of a first magnetic field experienced by the first magnetic field sensing element, wherein the first channel further comprises a switching circuit coupled to receive the first magnetic field signal and configured to generate a sampled signal, and wherein the switching circuit comprises a chopping circuit configured to chop the first magnetic field sensing element; a second channel comprising a second magnetic field sensing element supported by the substrate and configured to generate a second magnetic field signal indicative of a second magnetic field experienced by the second magnetic field sensing element; and at least one shield configured to reduce a bandwidth of the first magnetic field by a first amount and to reduce a bandwidth of the second magnetic field by a second amount. ### Claim 22 (depends on 21) The magnetic field sensor of claim 21, wherein the first channel is further configured to generate a first sensor output signal based on the first magnetic field signal and the second channel is further configured to generate a second sensor output signal based on the second magnetic field signal. ### Claim 23 (depends on 21) The magnetic field sensor of claim 21, further comprising a processor coupled to receive the first magnetic field signal and the second magnetic field signal and configured to generate a combined sensor output signal based on the first magnetic field signal and the second magnetic field signal. ### Claim 24 (depends on 23) The magnetic field sensor of claim 23, further comprising: a first signal path configured to carry a low frequency signal extracted from the second magnetic field signal from the second channel to the first channel; and a second path configured to carry an offset-compensated signal from the first channel to the second channel to compensate for an offset associated with the second magnetic field signal. ### Claim 25 A magnetic field sensor comprising: a substrate; a first channel comprising a first magnetic field sensing element supported by the substrate and configured to generate a first magnetic field signal indicative of a first magnetic field experienced by the first magnetic field sensing element, wherein the first channel further comprises a switching circuit coupled to receive the first magnetic field signal and configured to generate a sampled signal, and wherein the switching circuit comprises an analog-to-digital converter configured to convert the first magnetic field signal into a digital signal; a second channel comprising a second magnetic field sensing element supported by the substrate and configured to generate a second magnetic field signal indicative of a second magnetic field experienced by the second magnetic field sensing element; and at least one shield configured to reduce a bandwidth of the first magnetic field by a first amount and to reduce a bandwidth of the second magnetic field by a second amount. ### Claim 26 (depends on 25) The magnetic field sensor of claim 25, wherein the first channel is further configured to generate a first sensor output signal based on the first magnetic field signal and the second channel is further configured to generate a second sensor output signal based on the second magnetic field signal. ### Claim 27 (depends on 25) The magnetic field sensor of claim 25, further comprising a processor coupled to receive the first magnetic field signal and the second magnetic field signal and configured to generate a combined sensor output signal based on the first magnetic field signal and the second magnetic field signal. ### Claim 28 (depends on 27) The magnetic field sensor of claim 27, further comprising: a first signal path configured to carry a low frequency signal extracted from the second magnetic field signal from the second channel to the first channel; and a second path configured to carry an offset-compensated signal from the first channel to the second channel to compensate for an offset associated with the second magnetic field signal. ### Claim 29 A magnetic field sensor comprising: a substrate; a first channel comprising a first magnetic field sensing element supported by the substrate and configured to generate a first magnetic field signal indicative of a first magnetic field experienced by the first magnetic field sensing element; a second channel comprising a second magnetic field sensing element supported by the substrate and configured to generate a second magnetic field signal indicative of a second magnetic field experienced by the second magnetic field sensing element; and at least one shield configured to reduce a bandwidth of the first magnetic field by a first amount and to reduce a bandwidth of the second magnetic field by a second amount; and a lead frame supporting the substrate, wherein the at least one shield comprises a die attach pad of the lead frame that is disposed under the first magnetic field sensing element and is not disposed under the second magnetic field sensing element. ### Claim 30 (depends on 29) The magnetic field sensor of claim 29, wherein the first channel further comprises a switching circuit coupled to receive the first magnetic field signal and configured to generate a sampled signal. ### Claim 31 (depends on 30) The magnetic field sensor of claim 30, wherein the at least one shield is configured to reduce aliasing of the sampled signal. ### Claim 32 (depends on 30) The magnetic field sensor of claim 30, wherein the switching circuit comprises a chopping circuit configured to chop the first magnetic field sensing element. ### Claim 33 (depends on 30) The magnetic field sensor of claim 30, wherein the switching circuit comprises an analog-to-digital converter configured to convert the first magnetic field signal into a digital signal. ### Claim 34 (depends on 29) The magnetic field sensor of claim 29, wherein the first channel is further configured to generate a first sensor output signal based on the first magnetic field signal and the second channel is further configured to generate a second sensor output signal based on the second magnetic field signal. ### Claim 35 (depends on 29) The magnetic field sensor of claim 29, further comprising a processor coupled to receive the first magnetic field signal and the second magnetic field signal and configured to generate a combined sensor output signal based on the first magnetic field signal and the second magnetic field signal. ### Claim 36 (depends on 35) The magnetic field sensor of claim 35, further comprising: a first signal path configured to carry a low frequency signal extracted from the second magnetic field signal from the second channel to the first channel; and a second path configured to carry an offset-compensated signal from the first channel to the second channel to compensate for an offset associated with the second magnetic field signal. ### Claim 37 A magnetic field sensor comprising: a substrate; a first channel comprising a first magnetic field sensing element supported by the substrate and configured to generate a first magnetic field signal indicative of a first magnetic field experienced by the first magnetic field sensing element; a second channel comprising a second magnetic field sensing element supported by the substrate and configured to generate a second magnetic field signal indicative of a second magnetic field experienced by the second magnetic field sensing element; and at least one shield configured to reduce a bandwidth of the first magnetic field by a first amount and to reduce a bandwidth of the second magnetic field by a second amount, wherein the at least one shield comprises a conductive layer disposed over the first magnetic field sensing element and not disposed over the second magnetic field sensing element. ### Claim 38 (depends on 37) The magnetic field sensor of claim 37, wherein the first channel further comprises a switching circuit coupled to receive the first magnetic field signal and configured to generate a sampled signal. ### Claim 39 (depends on 38) The magnetic field sensor of claim 38, wherein the at least one shield is configured to reduce aliasing of the sampled signal. ### Claim 40 (depends on 38) The magnetic field sensor of claim 38, wherein the switching circuit comprises a chopping circuit configured to chop the first magnetic field sensing element. ### Claim 41 (depends on 38) The magnetic field sensor of claim 38, wherein the switching circuit comprises an analog-to-digital converter configured to convert the first magnetic field signal into a digital signal. ### Claim 42 (depends on 37) The magnetic field sensor of claim 37, wherein the first channel is further configured to generate a first sensor output signal based on the first magnetic field signal and the second channel is further configured to generate a second sensor output signal based on the second magnetic field signal. ### Claim 43 (depends on 37) The magnetic field sensor of claim 37, further comprising a processor coupled to receive the first magnetic field signal and the second magnetic field signal and configured to generate a combined sensor output signal based on the first magnetic field signal and the second magnetic field signal. ### Claim 44 (depends on 43) The magnetic field sensor of claim 43, further comprising: a first signal path configured to carry a low frequency signal extracted from the second magnetic field signal from the second channel to the first channel; and a second path configured to carry an offset-compensated signal from the first channel to the second channel to compensate for an offset associated with the second magnetic field signal. ### Claim 45 (depends on 37) The magnetic field sensor of claim 37, wherein the at least one shield is a solid or patterned conductive layer. ### Claim 46 A method comprising: generating a first magnetic field signal indicative of a first magnetic field experienced by a first magnetic field sensing element, the first magnetic field sensing element supported by a substrate; generating a second magnetic field signal indicative of a second magnetic field experienced by a second magnetic field sensing element, the second magnetic field sensing element supported by the substrate; reducing a bandwidth of the first magnetic field by a first amount using at least one shield; reducing a bandwidth of the second magnetic field by a second amount using the at least one shield; and generating a sampled signal from the first magnetic field signal and reducing aliasing of the sampled signal. ### Claim 47 A method comprising: generating a first magnetic field signal indicative of a first magnetic field experienced by a first magnetic field sensing element, the first magnetic field sensing element supported by a substrate; generating a second magnetic field signal indicative of a second magnetic field experienced by a second magnetic field sensing element, the second magnetic field sensing element supported by the substrate; reducing a bandwidth of the first magnetic field by a first amount using at least one shield; reducing a bandwidth of the second magnetic field by a second amount using the at least one shield; and chopping the first magnetic field sensing element.