Calibration and compensation method and apparatus for resistive sensor measurement bridge
A resistive sensor read-out apparatus is disclosed. In one embodiment, the resistive sensor read-out apparatus comprises an active sensor, a reference element, a bias circuit, a current-to-voltage converter, an analog-to-digital converter and a calibration processor. The bias circuit is coupled to the active sensor and the reference element and configured to calibrate one or more mismatches between the active sensor and the reference element. The current-to-voltage converter is coupled to an output of the bias circuit. The analog-to-digital converter is coupled to an output of the current-to-voltage converter. The calibration processor is coupled to an output of the analog-to-digital converter and configured to estimate an error caused by limited resolution mismatch calibration. The calibration processor is also configured to at least partially control calibration performed at the bias circuit based on the error.
1. A resistive sensor read-out apparatus, comprising:
an active sensor;
a reference element;
a bias circuit coupled to the active sensor and the reference element, the bias circuit configured to calibrate one or more mismatches between the active sensor and the reference element;
a current-to-voltage converter coupled to an output of the bias circuit;
an analog-to-digital converter coupled to an output of the current-to-voltage converter; and
a calibration processor coupled to an output of the analog-to-digital converter and configured to estimate an error caused by limited resolution mismatch calibration, the calibration processor configured to at least partially control calibration performed at the bias circuit based on the error.
2. The apparatus of claim 1 , wherein the bias circuit is an adjustable current mirror configured to calibrate mismatches between the active sensor and the reference element based on digital control thereof.
3. The apparatus of claim 1 , wherein the calibration processor is configured to identify effects of quantization errors in the bias circuit.
4. The apparatus of claim 1 , wherein the calibration processor is configured to identify effects of quantization errors in the bias circuit based on the output of the analog-to-digital converter.
5. The apparatus of claim 1 , wherein the calibration processor is configured to cancel effects of quantization errors in the bias circuit.
6. The apparatus of claim 1 , wherein the calibration processor is configured to cancel effects of quantization errors in the bias circuit based on the output of the analog-to-digital converter.
7. The apparatus of claim 1 , wherein the calibration processor is configured to identify effects of non-linearities in the bias circuit.
8. The apparatus of claim 1 , wherein the calibration processor is configured to identify effects of non-linearities in the bias circuit based on the output of the analog-to-digital converter.
9. The apparatus of claim 1 , wherein the calibration processor is configured to cancel effects of non-linearities in the bias circuit.
10. The apparatus of claim 1 , wherein the calibration processor is configured to cancel effects of non-linearities in the bias circuit based on the output of the analog-to-digital converter.
11. The apparatus of claim 1 , wherein the calibration processor is configured to characterize and store non-linearities of the bias circuit in a look-up table.
12. A resistive sensor read-out apparatus, comprising:
an active sensor;
a reference element;
an adjustable current mirror coupled to the active sensor and the reference element, the adjustable current mirror configured to calibrate mismatches between the active sensor and the reference element;
a current-to-voltage converter coupled to an output of the adjustable current mirror;
an analog-to-digital converter coupled to an output of the current-to-voltage converter; and
a digital signal processor coupled to an output of the analog-to-digital converter, the digital signal processor having at least one look-up table, a calibration processor, at least one arithmetic block, and a quantizer, the digital signal processor configured to at least partially control calibration performed at the adjustable current mirror.
13. The apparatus of claim 12 , wherein the look-up table is used to store current estimate coefficients of the reference element.
14. The apparatus of claim 12 , wherein the calibration processor is configured to identify quantization errors caused by limited resolution mismatch calibration.
15. The apparatus of claim 12 , wherein the at least one arithmetic block is configured to cancel quantization errors caused by limited resolution mismatch calibration.
16. The apparatus of claim 12 , wherein the quantizer is configured to convert high-to-low resolution coefficients.
17. A method for calibrating and compensating a resistive sensor read-out, comprising the steps of:
providing an active sensor;
providing a reference element;
providing a bias circuit for biasing the active sensor and the reference element;
determining a mismatch between the active sensor and the reference element;
identifying effects of limited resolution in the bias circuit based on the mismatch between the active sensor and the reference element; and
correcting the effects of limited resolution in the bias circuit.
18. The method of claim 17 further comprising a step of converting the mismatch between the active sensor and the reference element into digital form.
19. The method of claim 17 , wherein the bias circuit is adjustably configured to bias the active sensor and the reference element at least partially based on the effects of limited resolution in the bias circuit.
20. The method of claim 17 , wherein the bias circuit is an adjustable current mirror.