Method of interfacing a lc sensor and related system

Patent metadata

Field	Value
Publication number	US-2016011291-A1
Application number	US-201514739195-A
Country	US
Kind code	A1
Filing date	Jun 15, 2015
Priority date	Jul 9, 2014
Publication date	Jan 14, 2016
Grant date	—

Abstract

A method of interfacing a LC sensor with a control unit is provided. The control unit may include first and second contacts, where the LC sensor is connected between the first and the second contact. A capacitor is connected between the first contact and a ground. To start the oscillation of the LC sensor, the method may include during a first phase, connecting the first contact to a supply voltage and placing the second contact in a high impedance state such that the capacitor is charged through the supply voltage. During a second phase, the first contact may be placed in a high impedance state, and the second contact connected to the ground such that the capacitor transfers charge towards the LC sensor. During a third phase, the first contact and the second contact may be placed in a high impedance state so the LC sensor is able to oscillate.

First claim

1 - 12 . (canceled)

13 . A method of interfacing an LC sensor with a controller, the controller comprising first and second contacts with the LC sensor being coupled between the first and said second contacts of the controller and a capacitor being coupled between the first contact and a reference voltage, the method comprising:
during a first phase, connecting the first contact to a supply voltage and placing the second contact in a high impedance state so that the capacitor is charged through the supply voltage; during a second phase, placing the first contact in the high impedance state and connecting the second contact to the reference voltage so that the capacitor transfers charge to the LC sensor; and during a third phase, placing the first contact and the second contact in the high impedance state so that the LC sensor oscillates.

14 . The method of claim 13 further comprising monitoring a voltage at the second contact during the third phase.

15 . The method of claim 14 further comprising varying a duration of the second phase to regulate the voltage at the capacitor at the beginning of the third phase to define a middle point voltage of the oscillation occurring at the second contact.

16 . The method of claim 15 wherein the reference voltage comprises a first reference voltage; and wherein monitoring the voltage at the second contact comprises comparing the voltage at the second contact with at least one second reference voltage to generate a comparison signal.

17 . The method of claim 16 wherein monitoring the voltage at said second contact comprises counting a number of pulses in the comparison signal.

18 . The method of claim 17 wherein varying the duration of the second phase to regulate the voltage at the capacitor at the beginning of the third phase comprises varying the duration of the second phase to ensure a minimum number of pulses in the comparison signal.

19 . The method of claim 16 wherein the comparison signal comprises a first comparison signals, and further comprising:
monitoring the voltage at the first contact with a Schmitt Trigger so that a second comparison signal is set to high when the voltage at the first contact is above a given upper threshold, and to low when the voltage at the first contact is below a given lower threshold; and
performing a calibration.

20 . The method of claim 19 wherein performing the calibration comprises:
during a first calibration phase, connecting the first contact to the supply voltage and placing the second contact in the high impedance state that the capacitor is charged through the supply voltage;
during a second calibration phase, placing the first contact in a high impedance state and connecting the second contact to the first reference voltage so that the capacitor transfers charge to the LC sensor;
during a third calibration phase, once the second comparison signal indicates that the voltage at the first contact is below the given lower threshold, connecting the first contact to a supply voltage so that the capacitor is charged through the supply voltage; and
during a fourth calibration phase, once the second comparison signal indicates that the voltage at the first contact is above the given upper threshold, determining the duration of the third calibration phase.

21 . The method of claim 20 wherein between the second calibration phase and the third calibration phase, once the second comparison signal indicates that the voltage at the first contact is below the given lower threshold, further comprising connecting the first contact to the supply voltage so that the capacitor is recharged through the supply voltage, wherein the recharge duration is determined as a function of the duration of the second calibration phase to define the middle point voltage of the oscillation occurring at the second contact.

22 . A system comprising:
an LC sensor; a controller comprising first and second contacts with the LC sensor being coupled between the first and said second contacts of the controller; and a capacitor coupled between the first contact and a reference voltage; said controller being configured to
during a first phase, connect the first contact to a supply voltage and place the second contact in a high impedance state so that the capacitor is charged through the supply voltage,
during a second phase, place the first contact in the high impedance state and connect the second contact to the reference voltage so that the capacitor transfers charge to the LC sensor, and
during a third phase, place the first contact and the second contact in the high impedance state so that the LC sensor oscillates.

23 . The system of claim 22 wherein said controller is further configured to monitor a voltage at the second contact during the third phase.

24 . The system of claim 23 wherein said controller is further configured to vary a duration of the second phase to regulate the voltage at the capacitor at the beginning of the third phase to define a middle point voltage of the oscillation occurring at the second contact.

25 . The system of claim 24 wherein the reference voltage comprises a first reference voltage; and wherein said controller monitors the voltage at the second contact by comparing the voltage at the second contact with at least one second reference voltage to generate a comparison signal.

26 . The system of claim 25 wherein said controller monitors the voltage at the second contact by counting a number of pulses in the comparison signal.

27 . The system of claim 26 wherein said controller varies the duration of the second phase to regulate the voltage at the capacitor at the beginning of the third phase by varying the duration of the second phase to ensure a minimum number of pulses in the comparison signal.

28 . The system of claim 27 wherein the comparison signal comprises a first comparison signal, and wherein said controller is further configured to:
monitor the voltage at the first contact so that a second comparison signal is set to high when the voltage at the first contact is above a given upper threshold, and to low when the voltage at the first contact is below a given lower threshold; and
perform a calibration.

29 . The system of claim 28 wherein said controller is configured to perform the calibration by:
during a first calibration phase, connecting the first contact to the supply voltage and placing the second contact in the high impedance state that the capacitor is charged through the supply voltage;
during a second calibration phase, placing the first contact in a high impedance state and connecting the second contact to the first reference voltage so that the capacitor transfers charge to the LC sensor;
during a third calibration phase, once the second comparison signal indicates that the voltage at the first contact is below the given lower threshold, connecting the first contact to a supply voltage so that the capacitor is charged through the supply voltage; and
during a fourth calibration phase, once the second comparison signal indicates that the voltage at the first contact is above the given upper threshold, determining the duration of the third calibration phase.

30 . The system of claim 22 wherein said controller comprises:
a first switch configured to selectively connect the first contact to the supply voltage or place the first contact in the high impedance state;
a second switch configured to selectively connect the second contact to the reference voltage or place the first contact in the

Assignees

• St Microelectronics Srl

Inventors

• Condorelli Riccardo
• Mangano Daniele

Classifications

• H02J7/345

  using capacitors as storage or buffering devices · CPC title

• G01R35/00

  Testing or calibrating of apparatus covered by the other groups of this subclass · CPC title

• G01D3/028

  mitigating undesired influences, e.g. temperature, pressure · CPC title

• G01R27/2605

  Measuring capacitance (capacitive sensors G01D5/24) · CPC title

• G01R27/02

  Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant (by measuring phase angle only G01R25/00) · CPC title