AC-coupled sensor signal conditioning circuit

• US 6,657,476 B1
• Filed: 07/09/2002
• Issued: 12/02/2003
• Est. Priority Date: 07/09/2002
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Bicking, Robert E.
• Primary Examiner(s): Lam, Tuan T.
• Application Number:
  US10/192,455
• Time in Patent Office: 511 Days
• Field of Search: 327/344, 327/345, 327/341, 327/510, 327/511, 360/55, 360/65
• US Class Current: 327/341
• CPC Class Codes: G01R 33/09 Magnetoresistive devices

Abstract

A method and apparatus for minimizing errors in a sensor device due to signal amplitude variation are disclosed herein. A signal output from the sensor device is amplified and, thereafter, AC-coupled to a comparator such that the amplification and AC-coupling of the signal minimize offset shift-related errors associated with the sensor device. The signal can be coupled to eliminate offset shifts due to component mismatches, calibration, aging and/or temperature associated with the sensor device. An AC-coupled sensor signal conditioning circuit is utilized to amplify the signal through an amplifier and then AC-couple the signal to a comparator.

Claims

1. A method for minimizing errors in a magnetic sensor device of an AC-coupled sensor signal conditional circuit due to signal amplitude variation, said method comprising the steps of:

generating a signal output from said magnetic sensor device comprising a magnetoresistive bridge circuit;

amplifying said signal output through an amplifier circuit of said AC-coupled sensor signal conditioning circuit to produce an amplified signal thereof;

filtering said amplified signal utilizing a low pass filter of said AC-coupled sensor signal conditioning circuit to produce a high-pass signal thereof; and

thereafter providing said high-pass signal as input to a comparator coupled to said low pass filter in order to minimize offset shift-related errors associated with said magnetic sensor device, such that an effective offset of said comparator is reduced by a gain of said amplifier circuit.

2. The method of claim 1 wherein said high-pass signal is provided as input to said comparator to eliminate an offset shift due to component mismatches associated with said magnetic sensor device.

3. The method of claim 1 wherein said high-pass signal is provided as input to said comparator to eliminate an offset shift due to a calibration of said magnetic sensor device.

4. The method of claim 1 wherein said high-pass signal is provided as input to said comparator to eliminate an offset shift due to a temperature associated with said magnetic device.

5. The method of claim 1 wherein said high-pass signal is provided as input to said comparator to eliminate an offset shift due to aging of said magnetic sensor device.

6. The method of claim 1 wherein said high-pass signal is provided as input to said comparator in order to minimize offset shift-related errors associated with said magnetic device.

7. The method of claim 1 further comprising the steps of:

configuring said amplifier circuit as a differential single-ended amplifier circuit comprising at least one op-amp device;

connecting a first end of a first resistor to said magnetic sensor device and a second end of said first resistor to a negative input of said op-amp device;

coupling a first end of a second resistor to said negative input of said op-amp device and a second end of said second resistor to an output of said op-amp device, wherein said amplified signal is generated at said output of said op-amp device;

connecting a first end of a third resistor to said magnetic sensor device and a second end of said third resistor to a positive input of said op-amp device; and

coupling said positive input of said op amp device to a fourth resistor which is connected to a fifth resistor and a sixth resistor, wherein said fifth resistor is coupled to a power supply and said sixth resistor is coupled to ground.

8. The method of claim 1 further comprising the steps of:

configuring said magnetoresistive bridge circuit to comprise a plurality of magnetoresistors of said AC-coupled sensor signal conditioning circuit.

9. The method of claim 1 further comprising the step of:

configuring said comparator to comprise an AC-coupled comparator circuit of said AC-coupled sensor signal conditioning circuit.

10. The method of claim 9 further comprising the steps of:

configuring said AC-coupled comparator circuit of said AC-coupled sensor signal conditioning circuit to comprise at least one op-amp device;

connecting a negative input of said op-amp device to a first end of a first capacitor and a second end of a first resistor, wherein said first capacitor further comprises a second end coupled to ground and said first resistor comprises a first end of said first resistor coupled to an output of said amplifier circuit of said AC-coupled sensor signal conditioning circuit;

coupling a positive input of said op-amp device to a second end of a second resistor, a first end of a third resistor and a first end of a second capacitor, wherein said second resistor includes a first end coupled to an output of said amplifier circuit, said third resistor includes a second coupled to an output of said comparator, and said second capacitor includes a second end coupled to said output of said comparator;

placing said third resistor and said second capacitor in parallel with one another, wherein said third resistor and said second capacitor are connected to one another at an output of said op-amp device.

11. A method for minimizing errors in a magnetic sensor device of an AC-coupled sensor signal conditioning circuit due to signal amplitude variation, said method comprising the steps of:

generating a signal output from said magnetic sensor device comprising a magnetoresistive bridge circuit that includes a plurality of magnetoresistors;

amplifying said signal output through an amplifier circuit of said AC-coupled sensor signal conditioning circuit to produce an amplified signal thereof;

filtering said amplified signal utilizing a low pass filter of said AC-coupled sensor signal conditioning circuit to produce a high-pass signal thereof;

thereafter providing said high-pass signal to a comparator of said AC-coupled sensor signal conditioning circuit, wherein said comparator comprises an AC-coupled comparator circuit that includes at least one op-amp device, such that an effective offset of said comparator is reduced by a gain of said amplifier circuit;

connecting a negative input of said op-amp device to a first end of a first capacitor and a second end of a first resistor, wherein said first capacitor further comprises a second end coupled to ground and said first resistor comprises a first end of said first resistor coupled to an output of said amplifier circuit of said AC-coupled sensor signal conditioning circuit;

coupling a positive input of said op-amp device to a second end of a second resistor, a first end of a third resistor and a first end of a second capacitor, wherein said second resistor includes a first end coupled to an output of said amplifier circuit, said third resistor includes a second coupled to an output of said comparator, and said second capacitor includes a second end coupled to said output of said comparator; and

placing said third resistor and said second capacitor in parallel with one another, wherein said third resistor and said second capacitor are connected to one another at an output of said op-amp device, thereby minimizing offset shift-related errors associated with said magnetic sensor device, including calibration, temperature, and aging effects thereof.

12. An apparatus for minimizing errors in a magnetic sensor device of an AC-coupled sensor signal conditioning circuit due to signal amplitude variation, said apparatus comprising:

said magnetic sensor device comprising a magnetoresistive bridge circuit from which a signal output is generated;

an amplifier circuit, which receives as input said signal output from said magnetic sensor device to produce an amplified signal thereof;

a low pass filter of said AC-coupled sensor signal conditioning circuit for filtering said amplified signal to produce a high-pass signal thereof; and

wherein said high-pass signal is provided as an input to a comparator coupled to said low pass filter in order to minimize offset shift-related errors associated with said magnetic sensor device, such that an effective offset of said comparator is reduced by a gain of said amplifier circuit.

13. The apparatus of claim 12 wherein said high-pass signal is AC-coupled to said comparator to eliminate an offset shift due to component mismatches associated with said magnetic sensor device.

14. The apparatus of claim 12 wherein said high-pass signal is AC-coupled to said comparator to eliminate an offset shift due to a calibration of said magnetic sensor device.

15. The apparatus of claim 12 wherein said high-pass signal is AC-coupled to said comparator to eliminate an offset shift due to a temperature associated with said magnetic sensor device.

16. The apparatus of claim 12 wherein said high-pass signal is AC-coupled to said comparator to eliminate an offset shift due to aging of said magnetic sensor device.

17. The apparatus of claim 12 wherein said high-pass signal is AC-coupled to said comparator, such that amplification and AC-coupling of said output signal minimizes offset shift-related errors associated with said magnetic sensor device.

18. The apparatus of claim 12 further comprising:

said amplifier circuit comprising a differential single-ended amplifier circuit that includes at least one op-amp device;

a first end of a first resistor connected to said magnetic sensor device and a second end (of said first resistor to a negative input of said at least one op-amp device;

a first end of a second resistor connected to said negative input of said at least one op-amp device and a second end of said second resistor to an output of said at least one op-amp device, wherein said amplified signal is generated at said output of said at least one op-amp device;

a first end of a third resistor connected to said magnetic sensor device and a second end of said third resistor to a positive input of said at least one op-amp device; and

said positive input of said op amp device coupled to a fourth resistor connected to a fifth resistor and a sixth resistor, wherein said fifth resistor is coupled to a power supply and said sixth resistor is coupled to ground.

19. The apparatus of claim 12 wherein said magnetoresistive bridge circuit of said AC-coupled sensor signal conditioning circuit comprises a plurality of magnetoresistors.

20. The apparatus of claim 12 wherein said comparator of said AC-coupled sensor signal conditioning circuit comprises an AC-coupled comparator circuit.

21. The apparatus of claim 20 further comprising:

said AC-coupled comparator circuit comprising at least one op-amp device;

a negative input of said op-amp device connected to a first end of a first capacitor and a second end of a first resistor, wherein said first capacitor further comprises a second end coupled to ground and said first resistor comprises a first end of said first resistor coupled to an output of said amplifier circuit of said AC-coupled sensor signal conditioning circuit;

a positive input of said op-amp device coupled to a second end of a second resistor, a first end of a third resistor and a first end of a second capacitor, wherein said second resistor includes a first end coupled to an output of said amplifier circuit, said third resistor includes a second coupled to an output of said comparator, and said second capacitor includes a second end coupled to said output of said comparator; and

said third resistor and said second capacitor configured in parallel with one another, wherein said third resistor and said second capacitor are connected to one another at an output of said at least one op-amp device.

22. An apparatus for minimizing errors in a magnetic sensor device of an AC-coupled sensor signal conditioning circuit due to signal amplitude variation, said apparatus comprising:

said magnetic sensor device a magnetoresistive bridge circuit that generates a signal output, wherein said magnetoresistive bridge circuit comprises a plurality of magnetoresistors;

an amplifier circuit of said AC-coupled sensor signal conditioning circuit wherein said amplifier circuit, receives as input said signal output from said magnetic sensor device to produce an amplified signal thereof;

a low pass filter of said AC-coupled sensor signal conditioning circuit, wherein said low pass filter filters said amplified signal to produce a high-pass signal thereof;

an AC-coupling for AC-coupling said high-pass signal to a comparator, wherein said comparator comprises an AC-coupled comparator circuit that includes at least one op-amp device, such that an effective offset of said comparator is reduced by a gain of said amplifier circuit;

a negative input of said op-amp device connected to a first end of a first capacitor and a second end of a first resistor, wherein said first capacitor further comprises a second end coupled to ground and said first resistor comprises a first end of said first resistor coupled to an output of said amplifier circuit of said AC-coupled sensor signal conditioning circuit;

a positive input of said op-amp device coupled to a second end of a second resistor, a first end of a third resistor and a first end of a second capacitor, wherein said second resistor includes a first end coupled to an output of said amplifier circuit, said third resistor includes a second coupled to an output of said comparator, and said second capacitor includes a second end coupled to said output of said comparator; and

said third resistor and said second capacitor configured in parallel with one another, wherein said third resistor and said second capacitor are connected to one another at an output of said at least one op-amp device, thereby minimizing offset shift-related errors associated with said magnetic sensor device, including calibration, temperature, and aging effects thereof.