Integrated magnetic field strap for signal isolator

• US 7,046,117 B2
• Filed: 01/15/2002
• Issued: 05/16/2006
• Est. Priority Date: 01/15/2002
• Status: Expired due to Fees

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Wan, Hong
• Primary Examiner(s): HOANG, TU BA
• Application Number:
  US10/047,207
• Publication Number:
  US 20030132826A1
• Time in Patent Office: 1,582 Days
• Field of Search: 338/32.R, 338/32.H, 338/34, 324/252, 296/101, 296/101.2, 257516-518
• US Class Current: 338/32.00R
• CPC Class Codes: B82Y 25/00 Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
• CPC Class Codes: G01R 33/093 using multilayer structures, e.g. giant magnetoresistance sensors thin magnetic films H01F10/00
• CPC Class Codes: G01R 33/096 anisotropic magnetoresistance sensors
• CPC Class Codes: H10B 61/00 Magnetic memory devices, e.g. magnetoresistive RAM [MRAM] devices
• CPC Class Codes: H10N 59/00 Integrated devices, or assemblies of multiple devices, comprising at least one galvanomagnetic or Hall-effect element covered by groups H10N50/00 - H10N52/00 MRAM devices H10B61/00

Abstract

An integrated signal isolator is provided to isolate first and second circuits. First, second, third, and fourth magnetoresistors of the isolator are coupled together so as to form a Wheatstone bridge. The first second, third, and fourth magnetoresistors are arranged so that the Wheatstone bridge is immune to uniform external magnetic fields having any direction. An input strap generates magnetic fields across the first, second, third and fourth magnetoresistors in response to a signal from the first circuit so that the Wheatstone bridge provides an output to the second circuit that is commensurate with the signal from the first circuit.

Claims

1. An integrated signal isolator having first and second ends, wherein the integrated signal isolator comprises:

first and second isolator input terminals to receive a signal to be isolated;

first and second isolator output terminals to provide an isolated output signal;

first and second power supply terminals;

first, second, third, and fourth magnetoresistors, wherein the first and second magnetoresistors are coupled in series from the first power supply terminal to the second power supply terminal and are longitudinally displace from one another, wherein the third and fourth magnetoresistors are coupled in series from the second power supply terminal to the first power supply terminal and are longitudinally displace from one another, wherein the first isolator output terminal is coupled to a junction between the first and second magnetoresistors, wherein the second isolator output terminal is coupled to a junction between the third and fourth magnetoresistors, and wherein the first and second power supply terminals cause a current to flow in a direction though the first, second, third, and fourth magnetoresistors; and

,

an input strap having at least one turn coupled between the first and second isolator input terminals, wherein the input strap has a first portion disposed adjacent to the first magnetoresistor and in closer proximity to the first magnetoresistor than to the second, third, and fourth magnetoresistors, a second portion disposed adjacent to the second magnetoresistor and in closer proximity to the second magnetoresistor than to the first, third, and fourth magnetoresistors, a third portion disposed adjacent to the third magnetoresistor and in closer proximity to the third magnetoresistor than to the first, second, and fourth magnetoresistors, and a fourth portion disposed adjacent to the fourth magnetoresistor and in closer proximity to the fourth magnetoresistor than to the first, second and third magnetoresistors so that a magnetic field is generated over the first and second magnetoresistors in one direction, and so that a magnetic field is generated over the third and fourth magnetoresistors in an opposite direction, wherein the current through the first portion of the input strap flows in a direction parallel to the direction of current flow through the first magnetoresistor, wherein the current through the second portion of the input strap flows in a direction parallel to the direction of current flow through the second magnetoresistors, wherein the current through the third portion of the input strap flows in a direction parallel to the direction of current flow through the third magnetoresistors, and wherein the current through the fourth portion of the input strap flows in a direction parallel to the direction of current flow through the fourth magnetoresistors.

2. The integrated signal isolator of claim 1 wherein the input strap includes a plurality of turns.

3. The integrated signal isolator of claim 2 wherein each of the first, second, third, and fourth magnetoresistors comprises a serpentine structure having a plurality of elongated magnetoresistive portions coupled end-to-end, wherein the elongated portions of the first and second magnetoresistors are in parallel to the first and second portions of the input strap, respectively, wherein the elongated portions of the third and fourth magnetoresistors are in parallel to the third and fourth portions of the input strap, respectively, wherein the first and second portions of the input strap carry current in a direction that is opposite to current carried by the third and fourth portions of the input strap, and wherein the first and second portions of the input strap are parallel to the third and fourth portions of the input strap.

4. The integrated signal isolator of claim 1 wherein each of the first, second, third, and fourth magnetoresistors comprises a serpentine structure having a plurality of elongated magnetoresistive portions coupled end-to-end, wherein the elongated portions of the first and second magnetoresistors are parallel to a the first and second portions of the input strap, respectively, wherein the elongated portions of the third and fourth magnetoresistors are parallel to the third and fourth portions of the input strap, respectively, wherein the first and second portions of the input strap carry current in a direction that is opposite to current carried by the third and fourth portions of the input strap, and wherein the first and second portions of the input strap are parallel to the third and fourth portions of the input strap.

5. The integrated signal isolator of claim 1 wherein the first, second, third, and fourth magnetoresistors are in a first layer, wherein the input strap is in a second layer, and wherein the first and second layers are separate layers.

6. The integrated signal isolator of claim 5 further comprising a dielectric between the input strap and the first, second, third, and fourth magnetoresistors.

7. The integrated signal isolator of claim 6 wherein the dielectric is a first dielectric, wherein the integrated signal isolator further comprises a second dielectric over the input strap, and wherein the first, second, third, and fourth magnetoresistors are formed over a substrate and under the first dielectric.

8. The integrated signal isolator of claim 1 further comprising a set-reset coil having a plurality of clockwise turns and a plurality of counterclockwise turns, wherein the set-reset coil momentarily sets and resets a direction of magnetization of the first, second, third, and fourth magnetoresistors, wherein each clockwise turn of the set-reset coil has a portion running across the first and fourth magnetoresistors, wherein each counterclockwise turn of the set-reset coil has a portion running across the second and third magnetoresistors, and wherein the clockwise and counterclockwise turns are arranged so that current supplied to the set-reset coil flows through the portions of each of the clockwise and counterclockwise turns in the same direction.

9. The integrated signal isolator of claim 1 further comprising a set-reset coil having a plurality of turns disposed with respect to the first, second, third, and fourth magnetoresistors so that the set-reset coil generates a momentary magnetic field across the first, second, third, and fourth magnetoresistors in the same direction.

17. The integrated signal isolator of claim 1 wherein the input strap is disposed with respect to the first, second, third, and fourth magnetoresistors so that, when input current flows between the first and second isolator input terminals, a resistance of the first magnetoresistor tracks a resistance of the third magnetoresistor, and a resistance of the second magnetoresistor tracks a resistance of the fourth magnetoresistor.

18. The integrated signal isolator of claim 1 further comprising a set/reset strap positioned to generate a momentary set/reset magnetic field over the magnetoresistors.

19. The integrated signal isolator of claim 18 wherein the set/reset strap perpendicularly crosses a length of the magnetoresistors in the same direction so as to carry current across the magnetoresistors in the same direction.

10. An integrated signal isolator having first and second ends, wherein the integrated signal isolator comprises:

first, second, third, and fourth magnetoresistors located between the first and second ends, wherein the first and second magnetoresistors are coupled in series from a first power supply terminal to a second power supply terminal and are longitudinally displaced from one another between the first and second ends, wherein the third and fourth magnetoresistors are coupled in series from the second power supply terminal to the first power supply terminal and are longitudinally displaced from one another between the first and second ends, wherein a junction between the third and fourth magnetoresistors is coupled to a first isolator output terminal, wherein a junction between the first and second magnetoresistors is coupled to a second isolator output terminal, and wherein the first and second power supply terminals cause a current to flow in a direction though the first, second, third, and fourth magnetoresistors; and

,

an input strap having at least one turn coupled between first and second isolator input terminals, wherein the at least one turn has a first portion extending from the first end to the second end and running lengthwise alongside only the first and second magnetoresistors and a second portion extending from the second end to the first end and running lengthwise alongside only the third and fourth magnetoresistors, wherein the at least one turn is arranged so that current supplied to the input strap flows through the first portion in a first direction from the first end to the second end and through the second portion in a second direction from the second end to the first end, wherein the first and second directions are substantially opposite to one another, and wherein the first and second directions of current flowing through the input strap are parallel to the direction of current flow through the first, second, third, and fourth magnetoresistors.

11. The integrated signal isolator of claim 10 wherein the input strap includes a plurality of turns.

12. The integrated signal isolator of claim 10 wherein the first, second, third, and fourth magnetoresistors are in a first layer, wherein the input strap is in a second layer, and wherein the first and second layers are separate layers.

13. The integrated signal isolator of claim 10 further comprising a dielectric between the input strap and the first, second, third, and fourth magnetoresistors.

14. The integrated signal isolator of claim 13 wherein the dielectric is a first dielectric, wherein the integrated signal isolator further comprises a second dielectric over the input strap, and wherein the first, second, third, and fourth magnetoresistors are formed over a substrate and under the input strap.

15. The integrated signal isolator of claim 11 further comprising a set-reset coil having a plurality of clockwise turns and a plurality of counterclockwise turns, wherein the set-reset coil momentarily sets and resets a direction of magnetization of first, second, third, and fourth magnetoresistors, wherein each clockwise turn of the set-reset coil has a portion running across the first and fourth magnetoresistors, wherein each counterclockwise turn of the set-reset coil has a portion running across the second and third magnetoresistors, and wherein the clockwise and counterclockwise turns are arranged so that current supplied to the set-reset coil flows through the portions of each of the clockwise and counterclockwise turns in the same direction.

16. The integrated signal isolator of claim 10 further comprising a set-reset coil having a plurality of turns disposed with respect to the first, second, third, and fourth magnetoresistors so that the set-reset coil generates a momentary magnetic field across the first, second, third, and fourth magnetoresistors in the same direction.

20. A semiconductor signal isolator having first and second ends, wherein the semiconductor signal isolator comprises:

first and second isolator input terminals;

first and second isolator output terminals;

first and second power supply terminals;

a semiconductor substrate;

first, second, third, and fourth magnetoresistors formed in at least one layer over the semiconductor substrate, wherein the first and second magnetoresistors are coupled in series from the first power supply terminal to the second power supply terminal, wherein the third and fourth magnetoresistors are coupled in series from the second power supply terminal to the first power supply terminal, wherein the first isolator output terminal is coupled to a junction between the first and second magnetoresistors, wherein the second isolator output terminal is coupled to a junction between the third and fourth magnetoresistors, and wherein the first and second power supply terminals cause a current to flow in a direction though the first, second, third, and fourth magnetoresistors;

an input strap formed in at least one layer over the semiconductor substrate, wherein the input strap has at least one turn coupled between the first and second isolator input terminals, wherein the input strap is disposed with respect to the first, second, third, and fourth magnetoresistors so that a magnetic field is generated over the first and second magnetoresistors in one direction, and so that a magnetic field is generated over the third and fourth magnetoresistors in an opposite direction, and wherein current flows through portions of the input strap that are immediately adjacent to the first, second, third, and fourth magnetoresistors in a direction parallel to the direction of current flow through the first, second, third, and fourth magnetoresistors; and

,

a dielectric between the input strap and the first, second, third, and fourth magnetoresistors.

21. An integrated signal isolator having first and second ends, wherein the integrated signal isolator comprises:

first and second isolator input terminals to receive a signal to be isolated;

first and second isolator output terminals to provide an isolated output signal;

first and second power supply terminals;

first, second, third, and fourth magnetoresistors, wherein the first and second magnetoresistors are coupled in series from the first power supply terminal to the second power supply terminal and are longitudinally displace from one another, wherein the third and fourth magnetoresistors are coupled in series from the second power supply terminal to the first power supply terminal and are longitudinally displace from one another, wherein the first isolator output terminal is coupled to a junction between the first and second magnetoresistors, wherein the second isolator output terminal is coupled to a junction between the third and fourth magnetoresistors, and wherein the first and second power supply terminals cause a current to flow in a direction though the first, second, third, and fourth magnetoresistors; and

,

an input strap having at least one turn coupled between the first and second isolator input terminals, wherein the input strap has a first portion disposed in relation to the first magnetoresistor so that an axis passing perpendicularly through a plane of the first portion and through a plane of the first magnetoresistor passes through the first portion and the first magnetoresistor, wherein the input strap has a second portion disposed in relation to the second magnetoresistor so that an axis passing perpendicularly through a plane of the second portion and through a plane of the second magnetoresistor passes through the second portion and the second magnetoresistor, wherein the input strap has a third portion disposed in relation to the third magnetoresistor so that an axis passing perpendicularly through a plane of the third portion and through a plane of the third magnetoresistor passes through the third portion and the third magnetoresistor, wherein the input strap has a fourth portion disposed in relation to the fourth magnetoresistor so that an axis passing perpendicularly through a plane of the fourth portion and through a plane of the fourth magnetoresistor passes through the fourth portion and the fourth magnetoresistor, wherein a current through the input strap generates a magnetic field over the first and second magnetoresistors in one direction and generates a magnetic field over the third and fourth magnetoresistors in an opposite direction, wherein the current through the first portion of the input strap flows in a direction parallel to the direction of current flow through the first magnetoresistor, wherein the current through the second portion of the input strap flows in a direction parallel to the direction of current flow through the second magnetoresistor, wherein the current through the third portion of the input strap flows in a direction parallel to the direction of current flow through the third magnetoresistor, and wherein the current through the fourth portion of the input strap flows in a direction parallel to the direction of current flow through the fourth magnetoresistor.

22. An integrated signal isolator having first and second ends, wherein the integrated signal isolator comprises:

first and second isolator input terminals to receive a signal to be isolated;

first and second isolator output terminals to provide an isolated output signal;

first and second power supply terminals;

first, second, third, and fourth magnetoresistors, wherein the first and second magnetoresistors are coupled in series from the first power supply terminal to the second power supply terminal, wherein the third and fourth magnetoresistors are coupled in series from the second power supply terminal to the first power supply terminal, wherein the first isolator output terminal is coupled to a junction between the first and second magnetoresistors, wherein the second isolator output terminal is coupled to a junction between the third and fourth magnetoresistors, and wherein the first and second power supply terminals cause a current to flow in a direction though the first, second, third, and fourth magnetoresistors; and

,

an input strap having at least one turn coupled between the first and second isolator input terminals, wherein a current through the input strap generates a magnetic field over the first and second magnetoresistors in one direction and generates a magnetic field over the third and fourth magnetoresistors in an opposite direction; and

,

a set-reset coil having a plurality of turns disposed with respect to the first, second, third, and fourth magnetoresistors so that the set-reset coil generates a momentary magnetic field across the first, second, third, and fourth magnetoresistors in the same direction.