Source: http://www.google.com/patents/US8080994?dq=6,373,753
Timestamp: 2014-08-21 18:45:16
Document Index: 470308283

Matched Legal Cases: ['art 1', 'art 2', 'art 1', 'art 2', 'art 3', 'art 4', 'art 5', 'art 6', 'art 7', 'art 8']

Patent US8080994 - Integrated current sensor - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign in<nobr>Advanced Patent Search</nobr>PatentsAn integrated current sensor includes a current conductor, a magnetic field transducer, and an electromagnetic shield. The magnetic field transducer includes a sensor die. The electromagnetic shield is disposed proximate to the sensor die. The electromagnetic shield has at least one feature selected...http://www.google.com/patents/US8080994?utm_source=gb-gplus-sharePatent US8080994 - Integrated current sensorAdvanced Patent SearchPublication numberUS8080994 B2Publication typeGrantApplication numberUS 12/261,629Publication dateDec 20, 2011Filing dateOct 30, 2008Priority dateMay 12, 2006Also published asUS20070279053, US20090058412Publication number12261629, 261629, US 8080994 B2, US 8080994B2, US-B2-8080994, US8080994 B2, US8080994B2InventorsWilliam P. Taylor, Michael C. Doogue, John Cummings, Vijay MangtaniOriginal AssigneeAllegro Microsystems, Inc.Export CitationBiBTeX, EndNote, RefManPatent Citations (96), Non-Patent Citations (60), Referenced by (3), Classifications (7), Legal Events (3) External Links: USPTO, USPTO Assignment, EspacenetIntegrated current sensorUS 8080994 B2Abstract An integrated current sensor includes a current conductor, a magnetic field transducer, and an electromagnetic shield. The magnetic field transducer includes a sensor die. The electromagnetic shield is disposed proximate to the sensor die. The electromagnetic shield has at least one feature selected to reduce an eddy current in the electromagnetic shield.
CROSS REFERENCE TO RELATED APPLICATIONS This application is a Continuation application of and claims the benefit under 35 U.S.C. �120 of U.S. application Ser. No. 11,776 242 filed Jul. 11, 2007 now abandoned, which application is a Continuation-in-Part application of and claims the benefit under 35 �120 of U.S. patent application Ser. No. 11/383,021 filed May 12, 2006 now abandoned.
BACKGROUND OF THE INVENTION As is known in the art, one type of conventional electrical current sensor uses a Hall effect magnetic field transducer in proximity to a current-carrying conductor. The Hall effect device generates an output signal having a magnitude proportional to the magnetic field induced by the current through the conductor. Typical current sensors of this type include a gapped toroid magnetic flux concentrator, with the Hall effect device positioned in the toroid gap. The Hall effect device and toroid are assembled in a housing, which is mountable on a printed circuit board. In use, a separate current-carrying conductor, such as a wire, is passed through the center of the toroid and is soldered to the printed circuit board, such as by soldering exposed ends of the wire to plated through-holes. Such devices tend to be undesirably large, both in terms of height and circuit board area.
It has also been found, in general, that accumulated charge can form at an interface between an integrated circuit encapsulation (e.g., plastic) and the substrate (sensor die) of the integrated circuit. This trapped charge tends to cause undesirable effects, for example �gate leakage� from the substrate of the integrated circuit, resulting in out-of-specification behavior of the integrated circuit. The �gate leakage� can be caused by a forward biased enhancement mode parasitic field effect transistor (FET), which forms due to accumulated charge over a floating epi-material pocket in the substrate of the integrated circuit.
SUMMARY OF THE INVENTION In accordance with one aspect of the present invention, a current sensor includes a current conductor for passing a current sensed by the current sensor. The current sensor also includes a magnetic field transducer proximate to the current conductor. The magnetic field transducer includes a sensor die with first and second opposing surfaces. The sensor die also has an end surface coupling the first and second opposing surfaces. The first surface of the sensor die supports a magnetic field sensing element. The current sensor also includes an electromagnetic shield proximate to the first surface of the sensor die. The electromagnetic shield has at least one feature selected to reduce an eddy current induced in the electromagnetic shield.
As described above for the magnetic field transducer 12 of FIG. 1B, the magnetic field transducer 12 can be provided in the form of an integrated circuit containing the sensor die 14 encapsulated with an electrically insulating material (not shown, see, e.g., encapsulation 30, FIG. 1B). The magnetic field transducer 12 can be provided in different package types, such as the �K� single in line (SIP) package having a thickness on the order of 1.0 mm or 1.6 mm.
In addition, the electromagnetic shield 604, when grounded or coupled to a voltage source, tends to remove or reduce the effect of trapped charge generated on the surface of the sensor die 14, and, in particular, trapped charge that forms at an interface between the passivation layer (602 or 604 depending upon manufacturing method described above) and the above-described encapsulation (e.g., 30, FIG. 1B). The trapped charge tends to cause undesirable effects, for example �gate leakage� from the sensor die 14, which can result in out-of-specification behavior of the magnetic field transducer 12. The �gate leakage� can be caused by a forward biased enhancement mode parasitic field effect transistor (FET), which forms due to accumulated charge over a floating epi-material pocket in the sensor die 14. The gate leakage can result in threshold voltage shifts in the parasitic FET.
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