Accurate and cost efficient linear hall sensor with digital output

• US 9,124,281 B2
• Filed: 02/21/2014
• Issued: 09/01/2015
• Est. Priority Date: 03/17/2011
• Status: Active Grant

• Current Assignee: Infineon Technologies AG
• Original Assignee: Infineon Technologies AG
• Inventors: Motz, Mario
• Primary Examiner(s): TSAI, CAROL S W
• Application Number:
  US14/185,961
• Publication Number:
  US 20140167990A1
• Time in Patent Office: 557 Days
• Field of Search: 702/190, 324/207.13, 324/207.25, 324/251, 324/76.77, 340/572.1, 340/572.4, 340/505, 341/110, 341/144, 341/155
• US Class Current: 1/1
• CPC Class Codes: G01R 33/0029 Treating the measured signals, e.g. removing offset or noise
• CPC Class Codes: G01R 33/072 Constructional adaptation of the sensor to specific applications
• CPC Class Codes: H03M 1/06 Continuously compensating for, or preventing, undesired influence of physical parameters periodically, e.g. by using stored correction values, H03M1/10
• CPC Class Codes: H03M 1/0836 of phase error, e.g. jitter
• CPC Class Codes: H03M 1/12 Analogue/digital converters H03M1/001 – H03M1/10 take precedence
• CPC Class Codes: H03M 1/48 Servo-type converters

Abstract

One embodiment of the present invention relates to a magnetic sensor circuit having a magnetic field sensor device configured to generate a digital signal proportional to an applied magnetic field. An analog-to-digital converter converts the analog signal to a digital signal that is provided to a digital signal processing unit, which is configured to digitally track the analog output signal. The digital tracking unit comprises a delay removal circuitry configured to generate a plurality of digital signal component corresponding to a chopping phase. A non-delayed offset compensated digital output signal may be generated within the chopping phase by mathematically operating upon (e.g., adding or subtracting) the plurality of digital signal components, generated by the delay removal circuitry.

Claims

1. A circuit, comprising:

a chopping generation circuit configured to receive an analog signal and to periodically switch a polarity of the analog signal to generate a chopped signal having different polarities in temporally adjacent chopping phases;

an analog-to-digital converter (ADC) configured to convert the chopped signal to a digital signal;

a digital signal processing unit comprising a delay removal circuitry configured to generate a first and second digital signal components from a same chopping phase of the digital signal, and a logic element configured to add or subtract the first and second digital signal components from the same chopping phase to generate an offset compensated digital output signal;

a first signal path configured to provide the digital signal from the ADC to the logic element as the first digital signal component; and

a second signal path having one or more delay removal elements configured to operate upon the digital signal to generate the second digital signal component, which is provided to the logic element.

2. The circuit of claim 1, wherein the chopping generation circuit is configured to modulate a base component of the analog signal without modulating an offset component of the analog signal, thereby causing the digital signal to comprise a high frequency modulated base component and a low frequency offset component.

3. The circuit of claim 1,

wherein the first signal path comprises one or more delay removal elements comprising a first register configured to store the first digital signal component comprising the digital signal, and

wherein the one or more delay removal elements in the second signal path comprise a second register configured to store the second digital signal component comprising the digital signal.

4. The circuit of claim 3, wherein the delay removal circuitry comprises additional signal paths, which respectively comprise an additional register configured to store additional digital signal components.

5. The circuit of claim 3,

wherein the one or more delay removal elements in the first signal path further comprise a first clamping element and the one or more delay removal elements in the second signal path further comprise a second clamping element, and

wherein the first clamping element and the second clamping element are configured to selectively stop tracking of the digital signal at one or more clock periods within selective chopping phases.

6. The circuit of claim 5,

wherein during a first chopping phase the first clamping element is configured to clamp tracking of the first digital signal component stored in the first register for one or more clock periods, and

wherein during an immediately subsequent second chopping phase the second clamping element is configured to clamp tracking of the second digital signal component stored in the second register for one or more first clock periods.

7. The circuit of claim 6,

wherein within the first chopping phase the second clamping element does not clamp tracking of the second digital signal component;

and

wherein within the second chopping phase the first clamping element does not clamp tracking of the first digital signal component.

8. The circuit of claim 1,

wherein the first signal path comprises a first digital chopping modulator configured to demodulate the digital signal and to provide the first digital signal component having a first low frequency base component and a first high frequency modulated offset component;

wherein the second signal path comprises;

a low pass filter configured to low pass filter the digital signal to generate a signal having a base component with substantially zero amplitude and a second low frequency offset component; and

a second digital chopping modulator configured to modulate the low frequency offset component to generate the second digital signal component having a second high frequency modulated offset component.

9. The circuit of claim 1,

wherein during a first chopping phase the chopping generation circuit is configured to provide an analog signal having a positive base signal component and a positive offset component to the ADC;

and

wherein during a second chopping phase the chopping generation circuit is configured to provide an analog signal having a negative base signal component and a positive offset component to the ADC.

10. A method for digitally tracking an analog signal, comprising:

generating an analog signal;

periodically switching a polarity of the analog signal to generate a chopped signal having different polarities in temporally adjacent chopping phases;

generating a tracked digital signal that tracks the chopped signal;

generating a first digital signal component from the tracked digital signal over a plurality of chopping phases, which has a value that is clamped for one or more clock periods of a first one of the plurality of chopping phases;

generating a second digital signal component from the tracked digital signal over a plurality of chopping phases, which has a value that is clamped for one or more clock periods of a second one of the plurality of chopping phases immediately subsequent to the first one of the plurality of chopping phases;

providing the first digital signal component to a first register within a first signal path that that is configured to store the first digital signal component, and providing the second digital signal component to a second register within a second signal path that is configured to store the second digital signal component; and

mathematically operating upon the first and second digital signal components to generate an offset compensated digital output signal.

11. The method of claim 10, wherein generating the first and second digital signal components comprises:

providing the tracked digital signal to the first signal path configured to provide the first digital signal component; and

providing the tracked digital signal to the second signal path comprising one or more delay removal elements configured to operate upon the tracked digital signal to provide the second digital signal component.

12. The method of claim 10, further comprising:

modulating a base component of the analog signal without modulating an offset component of the analog signal, thereby causing the digital signal to comprise a high frequency modulated base component and a low frequency offset component.

13. The method of claim 10,

wherein during a first chopping phase the chopped signal has a positive base signal component and a positive offset component;

and

wherein during a second chopping phase the chopped signal has a negative base signal component and a positive offset component.

14. A circuit, comprising:

a chopping generation circuit configured to receive an analog signal and to periodically switch a polarity of the analog signal to generate a chopped signal having different polarities in temporally adjacent chopping phases; and

an analog-to-digital converter (ADC) configured to convert the chopped signal to a digital signal; and

a digital tracking unit having an input coupled to an output of the chopping generation circuit and comprising;

a first signal path connected to the input and configured to provide a first digital signal component corresponding to a first chopping phase to a first input of a logic element;

a second signal path comprising a low-pass filtering element connected to the input, wherein the low-pass filtering element is configured to average signals from a plurality of chopping phases and to provide the averaged signals to a second input of the logic element as a second digital signal component;

wherein the logic element is configured to superimpose the second digital signal component from the first digital signal component to generate a non-delayed digital output signal.

15. The circuit of claim 14,

wherein the first signal path comprises a first digital chopping modulator configured to demodulate the digital signal and to provide the first digital signal component having a first low frequency base component and a first high frequency modulated offset component;

wherein the second signal path further comprises;

a second digital chopping modulator configured to modulate a low frequency offset component output from the low-pass filtering element to generate the second digital signal component having a second high frequency modulated offset component.

16. The circuit of claim 14, wherein the first digital signal component and the second digital signal component have amplitudes with opposite signs.

17. The circuit of claim 14, further comprising:

a plurality of registers, respective registers configured to store an un-delayed digital signal component and a delayed digital signal component corresponding to a specific chopping phase; and

a plurality of clamping elements, respective clamping elements coupled to an input of one of the plurality of registers and configured to selectively stop tracking of the digital signal stored in the one of the plurality of registers at one or more clock periods of selective chopping phases.

18. The circuit of claim 14, wherein during the first chopping phase a first clamping element coupled to a slave register is configured to stop tracking of the digital signal component stored in a first register for one or more clock periods, and a second clamping element coupled to a master register is configured to not stop tracking of the digital signal component stored in a second register.