Inductive sensing methods, devices and systems
A method can include in a first phase of a sensing operation, controlling at least a first switch to energize a sensor inductance; in a second phase of the sensing operation that follows the first phase, controlling at least a second switch to couple the sensor inductance to a first modulator capacitance to induce a first fly-back current from the sensor inductance, the first fly-back current generating a first modulator voltage at the first modulator capacitance, and in response to the first modulator voltage, controlling at least a third switch to generate a balance current that flows in an opposite direction to the fly-back current at the first modulator node. The first and second phases can be repeated to generate a first modulator voltage at the first modulator capacitance. the modulator voltage can be converted into a digital value representing the sensor inductance. Related devices and systems are also disclosed.
1. A method, comprising:
generating a modulator voltage at a modulating node, including
by operation of a current generating circuit, generating a balance current,
by operation of switching circuits,
periodically coupling an energizing voltage to a first node,
periodically coupling an inductance current path to the modulator node, and
periodically coupling the balance current to the modulator node; and
by operation of an analog-to-digital converter (ADC) circuit, converting the modulator voltage into a digital value; wherein
the switching circuits, the current generating circuit and the ADC circuit are formed with a same integrated circuit substrate.
2. The method of claim 1 , wherein generating the balance current includes, by operation of the switching circuits, periodically charging a reference capacitor.
3. The method of claim 2 , wherein:
a capacitance of the reference capacitance is configurable; and
generating the balance current further includes configuring the capacitance of the reference capacitor with a digital value.
4. The method of claim 1 , wherein:
the current generating circuit comprises a digital-to-analog converter (DAC) circuit; and
generating the balance current further includes configuring the DAC with a digital value.
5. The method of claim 1 , wherein:
periodically coupling the energizing voltage to the first node includes periodically enabling a first switch; and
periodically coupling the inductance current path to the modulator node includes periodically enabling a second switch while the first switch is disabled.
6. The method of claim 5 , wherein periodically coupling the balance current to the modulator node includes periodically enabling a third switch in response to the modulator voltage.
7. The method of claim 5 , wherein periodically coupling the balance current to the modulator node includes periodically enabling a third switch while the second switch is enabled.
8. A device, comprising:
a balance current generating circuit configured to generate a balance current;
a sequencer circuit configured to receive a clock signal and generate switch control signals in synchronism with the clock signal;
a switching circuit comprising a plurality of switches, the switching circuit configured to, in response to the switch controls signals,
periodically couple an energizing voltage to a first input/output (I/O),
periodically enable an inductance current path between a second I/O and a modulator node, and
periodically couple the balance current to the modulator node; and
an analog-to-digital converter (ADC) circuit configured to convert a modulator voltage at the modulator node into a digital value; wherein
the sequencer circuit, switching circuit and ADC circuit are formed with a same integrated circuit substrate.
9. The device of claim 8 , wherein the balance current generating circuit includes a reference capacitor having a capacitance configurable by a digital value.
10. The device of claim 8 , wherein the balance current generating circuit comprises a current digital-to-analog converter circuit.
11. The device of claim 8 , wherein:
the switching circuit includes
a first switch coupled to the first I/O, and
a second switch coupled to the second I/O;
the sequencer circuit is configured to generate
a first control signal configured to periodically enable and disable the first switch, and
a second control signal configured to periodically enable the second switch while the first switch is disabled.
12. The device of claim 8 , wherein:
the switching circuit includes a third switch coupled to the balance current generating circuit; and
the sequencer circuit is configured to generate a third control signal configured to periodically enable and disable the third switch in response to the modulator voltage.
13. The device of claim 8 , wherein the sequence circuit comprises logic circuits configured to logically combine at least the first control signal and the modulator voltage to generate the third control signal.
14. The device of claim 8 , wherein the ADC circuit comprises a sigma-delta modulator.
15. A system, comprising:
a sensor having a sensor inductance; and
an integrated circuit device including
a controller circuit configured to
generate a balance current,
periodically couple an energizing voltage to the sensor,
periodically couple the sensor to a modulator node to provide an inductance current at the modulator node, and
periodically couple the balance current to the modulator node; and
an analog-to-digital converter (ADC) circuit configured to convert a modulator voltage at the modulator node into a digital value.
16. The system of claim 15 , wherein the controller circuit is configured to generate the balance current in response to the modulator voltage.
17. The system of claim 15 , wherein:
the controller circuit includes
a first switch coupled between the sensor and a power supply node,
a second switch coupled between the sensor and the modulator node, and
a sequencing circuit configured to periodically enable and disable the first switch and enable the second switch while the first switch is disabled.
18. The system of claim 15 , wherein:
the controller circuit includes
a balance current generator,
a third switch coupled between the balance current generator and the modulator node, and
the sequencing circuit is configured to periodically enable the third switch in response to the modulator voltage.
19. The system of claim 15 , wherein:
the sensor includes a first sensor node and a second sensor node;
the integrated circuit device further includes
a first input/output (I/O) coupled the first sensor node,
a second I/O coupled to the second sensor node, and
a third I/O coupled to the second sensor; and
the controller circuit is configured to
periodically couple the first I/O to a power supply and the third I/O to a reference voltage, and
periodically couple the second I/O to the modulator node.
20. The system of claim 15 , wherein the ADC circuit comprises a sigma-delta modulator.