INTEGRATED CURRENT SENSOR

• US 20070279053A1
• Filed: 07/11/2007
• Published: 12/06/2007
• Est. Priority Date: 05/12/2006
• Status: Abandoned Application

• Current Assignee: Allegro Microsystems Incorporated (Sanken Electric Company Limited)
• Original Assignee: Allegro Microsystems Incorporated (Sanken Electric Company Limited)
• Inventors: Taylor, William, Sharma, Nirmal, Cummings, John, Doogue, Michael, Mangtani, Vijay, Gagnon, Jay
• Application Number:
  US11/776,242
• Publication Number:
  US 20070279053A1
• Time in Patent Office: Days
• US Class Current: 324/252
• CPC Class Codes: G01R 1/18 Screening arrangements against electric or magnetic fields, e.g. against earth's field
• CPC Class Codes: G01R 15/207 Constructional details independent of the type of device used
• CPC Class Codes: G01R 33/07 Hall effect devices
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48247 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2924/00012 Relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/181 Encapsulation

Abstract

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.

Claims

1. A current sensor, comprising:

a current conductor for carrying a current sensed by the current sensor,

a magnetic field transducer proximate to said current conductor, said magnetic field transducer comprising a sensor die with first and second opposing surfaces, the sensor die also having an end surface coupling the first and second opposing surfaces, wherein the first surface of the sensor die supports a magnetic field sensing element; and

an electromagnetic shield proximate to the first surface of the sensor die, wherein said electromagnetic shield has at least one feature selected to reduce an eddy current induced in said electromagnetic shield.

2. The current sensor of claim 1, wherein said current conductor is closer to the first surface of the sensor die than to the second surface of the sensor die.

3. The current sensor of claim 1, wherein said current conductor is closer to the end surface of the sensor die than to the first or second surfaces of the sensor die.

4. The current sensor of claim 1, wherein said electromagnetic shield is substantially planar and has a shape selected to reduce a path length of a closed loop current path in said electromagnetic shield.

5. The current sensor of claim 1, wherein said electromagnetic shield comprises a slot.

6. The current sensor of claim 1, wherein said electromagnetic shield comprises:

a central member; and

a plurality of non-overlapping members coupled to the central member.

7. The current sensor of claim 1, wherein said electromagnetic shield comprises a plurality of interdigitated members.

8. The current sensor of claim 1, wherein a position of the at least one feature relative to said magnetic field transducer is selected to reduce an affect of the eddy current upon the magnetic field transducer.

9. The current sensor of claim 1, further comprising an insulating layer disposed between the first surface of the sensor die and said electromagnetic shield.

10. The current sensor of claim 1, further comprising an insulating layer disposed at a position resulting in said electromagnetic shield being between said insulating layer and the sensor die.

11. The current sensor of claim 1, further comprising at least one amplifier disposed on the sensor die.

12. The current sensor of claim 1, wherein said current conductor has a first notch and a second notch substantially aligned with the first notch, wherein said magnetic field transducer has at least a portion disposed in the first notch, wherein the current sensor further includes a magnetic core having a central region and a pair of substantially parallel legs extending from the central region, wherein at least a portion of the central region is disposed in the second notch and wherein at least a portion of each leg covers at least a portion of a respective surface of the magnetic field sensing element.

13. The current sensor of claim 12, wherein the magnetic field sensing element comprises a Hall effect element.

14. The current sensor of claim 12, wherein the magnetic field sensing element comprises a magnetoresistance element.

15. The current sensor of claim 12, wherein a width of the portion of said magnetic field transducer disposed in the first notch is substantially equal to the width of the first notch so that said magnetic field transducer is in a substantially fixed position with respect to said current conductor.

16. The current sensor of claim 12, wherein the width of the central region of said magnetic core disposed in the second notch is substantially equal to the width of the second notch so that said magnetic core is in a substantially fixed position with respect to said current conductor.

17. The current sensor of claim 12, wherein each of the legs of said magnetic core covers substantially an entire surface of said magnetic field transducer.

18. The current sensor of claim 12, wherein the first and second notches are located in a central region of said current conductor and said current conductor comprises a mounting mechanism at end regions thereof.

19. The current sensor of claim 12, wherein said magnetic core is comprised of a material selected from the group consisting of ferrite, steel, iron, iron alloy, nickel, cobalt, and permalloy.

20. The current sensor of claim 12, further comprising a molded body encapsulating at least a portion of said magnetic field transducer, said current conductor, and said magnetic core.

21. The current sensor of claim 12, wherein the pair of substantially parallel legs are spaced by a distance substantially equal to a thickness of said magnetic field transducer.

22. The current sensor of claim 1, wherein said current conductor has a narrowed region, a tab, and an intermediate region extending from the narrowed region to the tab, wherein the narrowed region has opposing, substantially planar surfaces, wherein the intermediate region has opposing, substantially planar surfaces, wherein the opposing, substantially planar surfaces of the intermediate region are generally parallel to the opposing, substantially planar surfaces of the narrowed region, wherein the narrowed region comprises a notch in a first side of the narrowed region, wherein the tab is adapted to couple to a circuit board with the opposing, substantially planar surfaces of the narrowed region substantially parallel to the circuit board;

and

a magnetic core having a central region and a pair of substantially parallel legs extending from the central region, wherein a selected one of said magnetic field transducer or the central region of said magnetic core is disposed in the notch and wherein the other one of said magnetic field transducer or the central region of said magnetic core is adjacent to a second, opposite, side of the narrowed region so that the pair of legs straddles the opposing, substantially planar surfaces of the narrowed region with each leg covering at least a portion of a respective surface of the magnetic field sensing element.

23. The current sensor of claim 22, further comprising a molded body encapsulating at least a portion of said magnetic field transducer, said current conductor, and said magnetic core.

24. The current sensor of claim 22, wherein the magnetic field sensing element comprises a Hall effect element.

25. The current sensor of claim 22, wherein the magnetic field sensing element comprises a magnetoresistance element.

26. The current sensor of claim 22, wherein the tab is adapted to be inserted though a hole in a circuit board.

27. The current sensor of claim 26, wherein the tab comprises a plastically bent portion of said current conductor.

28. A current sensor, comprising:

a current conductor for carrying a current sensed by the current sensor;

a magnetic field transducer proximate to said current conductor, said magnetic field transducer comprising a sensor die with first and second opposing surfaces, the sensor die also having an end surface coupling the first and second opposing surfaces, wherein the first surface of the sensor die supports a magnetic field sensing element;

an electromagnetic shield proximate to the first surface of the sensor die; and

a magnetic core having a central region and a pair of substantially parallel legs extending from the central region, wherein the pair of legs straddles the current conductor with at least a portion of each leg covering at least a portion of a respective surface of the magnetic field sensing element.

29. The current sensor of claim 28, wherein said current conductor is closer to the first surface of the sensor die than to the second surface of the sensor die.

30. The current sensor of claim 28, wherein said current conductor is closer to the end surface of the sensor die than to the first or second surfaces of the sensor die.

31. The current sensor of claim 28, wherein said current conductor has a first notch and a second notch substantially aligned with the first notch, wherein said magnetic field transducer has at least a portion disposed in the first notch, wherein at least a portion of the central region of the magnetic core is disposed in the second notch.

32. The current sensor of claim 31, wherein a width of the portion of said magnetic field transducer disposed in the first notch is substantially equal to a width of the first notch so that said magnetic field transducer is in a substantially fixed position with respect to said current conductor, and wherein a width of the central region of said magnetic core disposed in the second notch is substantially equal to a width of the second notch so that said magnetic core is in a substantially fixed position with respect to said current conductor.

33. The current sensor of claim 28, wherein said current conductor has a narrowed region, a tab, and an intermediate region extending from the narrowed region to the tab, wherein the narrowed region has opposing, substantially planar surfaces, wherein the intermediate region has opposing, substantially planar surfaces, wherein the opposing, substantially planar surfaces of the intermediate region are generally parallel to the opposing, substantially planar surfaces of the narrowed region, wherein the narrowed region comprises a notch in a first side of the narrowed region, wherein the tab is adapted to couple to a circuit board with the opposing, substantially planar surfaces of the narrowed region substantially parallel to the circuit board, wherein a selected one of said magnetic field transducer or the central region of said magnetic core is disposed in the notch and wherein the other one of said magnetic field transducer or the central region of said magnetic core is adjacent to a second, opposite, side of the narrowed region so that the pair of legs straddles the opposing, substantially planar surfaces of the narrowed region.

34. The current sensor of claim 33, wherein a width of the selected one of said magnetic field transducer or the central region of said magnetic core disposed in the notch is substantially equal to a width of the first notch so that the selected one of said magnetic field transducer or the central region of said magnetic core is in a substantially fixed position with respect to said current conductor.

35. The current sensor of claim 28, further including first and second insulating layers, wherein said electromagnetic shield is disposed between the first and second insulating layers,