Device for controlling a capacitor having an adjustable capacitance

Patent metadata

Field	Value
Publication number	US-9859843-B2
Application number	US-201615252868-A
Country	US
Kind code	B2
Filing date	Aug 31, 2016
Priority date	Feb 10, 2016
Publication date	Jan 2, 2018
Grant date	Jan 2, 2018

Abstract

A first capacitor has a capacitance adjustable to a set point value by application of a bias voltage. A second capacitor also has a capacitance adjustable to a set point value by application of a bias voltage. The first and second capacitors are arranged to receive the same bias voltage generated by a control circuit. The control circuit receiving the set point value as an input and generates that bias voltage in response to a quantity representative of a capacitance of the second capacitor.

First claim

The invention claimed is:

1. A device, comprising:
a first capacitor having a capacitance that is adjustable to a set point value in response to application of a bias voltage;
a second capacitor having a capacitance that is adjustable to a set point value in response to application of a bias voltage, wherein the first and second capacitors are configured to receive a same bias voltage; and
a control circuit having an input to receive said set point value and configured to generate said bias voltage while taking into account a quantity representative of the capacitance of the second capacitor.

2. The device of claim 1 , wherein the first and second capacitors are matched to substantially have a same temperature variation.

3. The device of claim 1 , wherein the first and second capacitors are identical to within manufacturing dispersions.

4. The device of claim 1 , wherein the control circuit comprises:
a first oscillator circuit coupled to the second capacitor and configured to generate a first frequency varying according to the capacitance of the second capacitor; and
a feedback loop configured to adjust said bias voltage to control said first frequency to match a second frequency.

5. The device of claim 4 , wherein the first oscillator circuit comprises an adjustable resistor, and wherein a value of the first frequency is further dependent on a value of said adjustable resistor.

6. The device of claim 5 , wherein the value of said adjustable resistor is set according to said set point value.

7. The device of claim 4 , wherein the control circuit further comprises a second oscillator circuit coupled to a third capacitor and configured to generate said second frequency fixed by the capacitance of the third capacitor.

8. The device of claim 7 , wherein the third capacitor is a metal-ceramic-metal capacitor.

9. The device of claim 7 , wherein the second oscillator circuit comprises a non-adjustable resistor, and wherein a value of the second frequency is further dependent on the value of said non-adjustable resistor.

10. The device of claim 9 , wherein the first oscillator circuit comprises an adjustable resistor, and wherein a value of the first frequency is further dependent on a value of said adjustable resistor.

11. The device of claim 10 , wherein said adjustable resistor and said non-adjustable resistor are matched to have substantially the same temperature variation.

12. The device of claim 1 , wherein the first and second capacitors are integrated in a first integrated circuit chip comprising:
first and second terminals coupled to electrodes of the first capacitor;
a third terminal configured to receive said bias voltage; and
a fourth terminal coupled to an electrode of the second capacitor.

13. The device of claim 11 , wherein the control circuit is integrated in a second integrated circuit chip different from the first integrated circuit chip.

14. The device of claim 1 , wherein the first and second capacitors comprise Barium-Strontium-Titanium capacitors.

15. The device of claim 1 , wherein the control circuit comprises:
a first oscillator circuit coupled to the second capacitor and configured to generate a first frequency varying according to the capacitance of the second capacitor;
a second oscillator circuit coupled to a reference capacitor and configured to generate a second frequency fixed according to the capacitance of the reference capacitor;
a frequency difference circuit configured to receive the first and second frequencies and generate a control signal indicative of a magnitude of a difference between the first and second frequencies;
wherein said bias voltage is derived from said control signal.

16. The device of claim 15 , wherein the control circuit further comprises an amplifier circuit configured to amplify the control signal to generate said bias voltage.

17. The device of claim 15 , wherein the first oscillator circuit further comprises an adjustable resistor, and wherein a value of the first frequency is further dependent on a value of said adjustable resistor.

18. The device of claim 17 , wherein the value of said adjustable resistor is set according to said set point value.

19. A device, comprising:
a first integrated circuit chip including:
a first capacitor having a capacitance that is adjustable to a set point value in response to application of a bias voltage; and
a second capacitor having a capacitance that is adjustable to a set point value in response to application of a bias voltage, wherein the first and second capacitors are configured to receive a same bias voltage;
a reference capacitor; and
a second integrated circuit chip including:
a first oscillator circuit coupled to the second capacitor and configured to generate a first frequency varying according to the capacitance of the second capacitor;
a second oscillator circuit coupled to said reference capacitor and configured to generate a second frequency fixed according to the capacitance of the reference capacitor;
a frequency difference circuit configured to receive the first and second frequencies and generate a control signal indicative of a magnitude of a difference between the first and second frequencies;
a bias generator circuit figured to output said bias voltage in response to said control signal.

20. The device of claim 19 , wherein the first and second capacitors comprise Barium-Strontium-Titanium capacitors.

Assignees

• St Microelectronics Tours Sas

Inventors

• Charley Sylvain
• Heurtier Jerome
• Jeuffrault Laurent

Classifications

• H03L7/1075

  by changing characteristics of the loop filter, e.g. changing the gain, changing the bandwidth (H03L7/1072 takes precedence) · CPC title

• H03B2201/011

  the means being an element with a variable capacitance · CPC title

• H03B5/20 Primary

  with frequency-determining element comprising resistance and either capacitance or inductance, e.g. phase-shift oscillator · CPC title

• H01G7/06

  having a dielectric selected for the variation of its permittivity with applied voltage, i.e. ferroelectric capacitors (electrets H01G7/02) · CPC title

• G05F1/561 Primary

  Voltage to current converters (amplifiers H03F) · CPC title