Compensating for current splitting errors in a measurement system

1. A system comprising:

amplifier circuitry configured to drive an electromagnetic load with a driving signal; and

a processing system communicatively coupled to the electromagnetic load and configured to:

compensate for current-sensing error of the processing system caused by feedback circuitry of the amplifier circuitry; and

operate in a plurality of modes including:

a driving mode in which the amplifier circuitry generates a human-perceptible driving signal to the electromagnetic load; and

a load sensing mode of the system for sensing a physical quantity associated with the electromagnetic load in which the amplifier circuitry generates a pilot signal to the electromagnetic load and the physical quantity is based on a measured characteristic of the electromagnetic load in response to the pilot signal;

wherein the processing system is further configured to:

during the driving mode, couple a first terminal of the electromagnetic load to a ground voltage; and

during the load sensing mode:

couple the first terminal to a current-sensing circuit having a sense resistor coupled between the first terminal and an electrical node driven to a common-mode voltage; and

sense the physical quantity based on a voltage across the sense resistor.

2. The system of claim 1 , wherein the processing system is further configured to:

determine the current-sensing error at an electrical node of the system; and

modify the common-mode voltage as a function of the current-sensing error.

3. A system comprising:

amplifier circuitry configured to drive an electromagnetic load with a driving signal; and

a processing system communicatively coupled to the electromagnetic load and configured to:

compensate for current-sensing error of the processing system caused by feedback circuitry of the amplifier circuitry;

operate in a plurality of modes including:

a driving mode in which the amplifier circuitry generates a human-perceptible driving signal to the electromagnetic load; and

a load sensing mode of the system for sensing a physical quantity associated with the electromagnetic load in which the amplifier circuitry generates a pilot signal to the electromagnetic load and the physical quantity is based on a measured characteristic of the electromagnetic load in response to the pilot signal; and

compensate for current-sensing error of the processing system caused by feedback circuitry of the amplifier circuitry during the load sensing mode.

4. The system of claim 3 , wherein the processing system is further configured to:

determine the current-sensing error; and

supply a current corresponding to the current-sensing error to current-sensing circuitry of the processing system.

5. A system of claim 1 , comprising:

amplifier circuitry configured to drive an electromagnetic load with a driving signal; and

a processing system communicatively coupled to the electromagnetic load and configured to:

compensate for current-sensing error of the processing system caused by feedback circuitry of the amplifier circuitry;

estimate a split current flowing in the feedback circuitry based on a monitored voltage; and

apply a compensation based on the split current to a measured current associated with the electromagnetic load to estimate a load current flowing through the electromagnetic load.

6. The system of claim 5 , wherein the physical quantity is a complex impedance of the electromagnetic load and the processing system and further configured to estimate the complex impedance based on the monitored voltage and a combination of the measured current and the compensation.

7. The system of claim 6 , wherein the processing system is further configured to:

apply the compensation to the measured current in the time domain to generate the combination;

transform the monitored voltage from the time domain to a frequency-domain voltage vector;

transform the combination from the time domain to a frequency-domain current vector; and

estimate the complex impedance based on the frequency-domain voltage vector and the frequency-domain current vector.

8. The system of claim 6 , wherein the processing system is further configured to:

transform the monitored voltage from the time domain to a frequency-domain voltage vector;

transform the measured current from the time domain to a frequency-domain current vector;

apply the compensation to the frequency-domain current vector in the frequency domain to generate the combination; and

estimate the complex impedance based on the frequency-domain voltage vector and the combination.

9. A method comprising:

driving, with amplifier circuitry, an electromagnetic load with a driving signal;

compensating for current-sensing error of a processing system communicatively coupled to the electromagnetic load, wherein the current-sensing error is caused by feedback circuitry of the amplifier circuitry;

operating the processing system in a plurality of modes including:

a driving mode in which the amplifier circuitry generates a human-perceptible driving signal to the electromagnetic load; and

a load sensing mode of the system for sensing a physical quantity associated with the electromagnetic load in which the amplifier circuitry generates a pilot signal to the electromagnetic load and the physical quantity is based on a measured characteristic of the electromagnetic load in response to the pilot signal;

during the driving mode, coupling a first terminal of the electromagnetic load to a ground voltage; and

during the load sensing mode:

coupling the first terminal to a current-sensing circuit having a sense resistor coupled between the first terminal and an electrical node driven to a common-mode voltage; and

sensing the physical quantity based on a voltage across the sense resistor.

10. The method of claim 9 , further comprising:

determining the current-sensing error at an electrical node of the system; and

modifying the common-mode voltage as a function of the current-sensing error.

11. A method comprising:

driving, with amplifier circuitry, an electromagnetic load with a driving signal;

compensating for current-sensing error of a processing system communicatively coupled to the electromagnetic load, wherein the current-sensing error is caused by feedback circuitry of the amplifier circuitry;

operating the processing system in a plurality of modes including:

a driving mode in which the amplifier circuitry generates a human-perceptible driving signal to the electromagnetic load; and

a load sensing mode of the system for sensing a physical quantity associated with the electromagnetic load in which the amplifier circuitry generates a pilot signal to the electromagnetic load and the physical quantity is based on a measured characteristic of the electromagnetic load in response to the pilot signal; and

compensating for current-sensing error of the processing system caused by feedback circuitry of the amplifier circuitry during the load sensing mode.

12. The method of claim 11 , further comprising:

determining the current-sensing error; and

supplying a current corresponding to the current-sensing error to current-sensing circuitry of the processing system.

13. A method comprising:

driving, with amplifier circuitry, an electromagnetic load with a driving signal;

compensating for current-sensing error of a processing system communicatively coupled to the electromagnetic load, wherein the current-sensing error is caused by feedback circuitry of the amplifier circuitry;

estimating a split current flowing in the feedback circuitry based on a monitored voltage; and

applying a compensation based on the split current to a measured current associated with the electromagnetic load to estimate a load current flowing through the electromagnetic load.

14. The method of claim 13 , wherein the physical quantity is a complex impedance of the electromagnetic load and the method further comprises estimating the complex impedance based on the monitored voltage and a combination of the measured current and the compensation.

15. The method of claim 14 , further comprising:

applying the compensation to the measured current in the time domain to generate the combination;

transforming the monitored voltage from the time domain to a frequency-domain voltage vector;

transforming the combination from the time domain to a frequency-domain current vector; and

estimating the complex impedance based on the frequency-domain voltage vector and the frequency-domain current vector.

16. The method of claim 14 , further comprising:

transforming the monitored voltage from the time domain to a frequency-domain voltage vector;

transforming the measured current from the time domain to a frequency-domain current vector;

applying the compensation to the frequency-domain current vector in the frequency domain to generate the combination; and

estimating the complex impedance based on the frequency-domain voltage vector and the combination.