Directional capacitive proximity sensor with bootstrapping

• US 9,176,597 B2
• Filed: 07/02/2012
• Issued: 11/03/2015
• Est. Priority Date: 07/02/2012
• Status: Active Grant

• Current Assignee: STMicroelectronics International N.V. (STMicroelectronics NV)
• Original Assignee: STMicroelectronics Asia Pacific Pte Limited (STMicroelectronics NV)
• Inventors: Soo, Jenn Woei, Tan, Kien Beng
• Primary Examiner(s): Assouad, Patrick
• Assistant Examiner(s): BROWN, LAMARR A
• Application Number:
  US13/539,731
• Publication Number:
  US 20140004905A1
• Time in Patent Office: 1,219 Days
• Field of Search: 324/548, 324658-690
• US Class Current: 1/1
• CPC Class Codes: G01B 7/023 for measuring distance between sensor and object G01B7/082 and G01B7/102 take precedence
• CPC Class Codes: G06F 3/03 Arrangements for converting the position or the displacement of a member into a coded form

Abstract

A directional capacitive proximity sensor circuit capable of providing directional capacitive proximity sensing includes one or more guard electrodes, a first sensor, and a second sensor. The directional capacitive proximity sensor is installed in a device such that the first sensor is positioned near a first component of the device, and the second sensor is positioned near a second component of the device. The first and second sensors measure a capacitance to detect proximity of a user relative to the respective sensor, wherein the detected proximity is interpreted to determine a direction in which the user proximity is detected relative to the directional capacitive proximity sensor circuit. The guard electrode is provided to mitigate stray capacitance to reduce error in the capacitance measurements obtained by the first and second sensors.

Claims

1. A directional capacitive proximity sensing circuit for use with a mobile device, comprising:

one or more guard electrodes;

first capacitive sensor circuitry operable to sense a first capacitance and produce a first capacitive sensor reading responsive to the sensed first capacitance and indicative of detection of a user proximate to the first capacitive sensor, wherein the first capacitive sensor circuitry includes a first capacitive sensor capacitively coupled to a first section of at least one of the one or more guard electrodes;

second capacitive sensor circuitry operable to sense a second capacitance and produce a second capacitive sensor reading responsive to the sensed second capacitance and indicative of detection of the user proximate to the second capacitive sensor, wherein the second capacitive sensor circuitry includes a second capacitive sensor capacitively coupled to a second section of at least one of the one or more guard electrodes; and

output circuitry configured to receive and compare the first and second capacitive sensor readings and produce an output signal to indicate detection of the user proximate to the mobile device in a location nearer the first capacitive sensor than the second capacitive sensor when the sensed first capacitance is different than the sensed second capacitance.

2. The directional capacitive proximity sensing circuit as set forth in claim 1, wherein the first capacitive sensor circuitry further comprises a first switched integrator circuit operable during a first phase to apply a voltage to the first capacitive sensor, and operable during a second phase to transfer the first capacitance to a first capacitor and generate the first capacitive sensor reading.

3. The directional capacitive proximity sensing circuit as set forth in claim 1, wherein the second capacitive sensor circuitry further comprises a second switched integrator circuit operable during a first phase to apply a voltage to the second capacitive sensor, and operable during a second phase to transfer the second capacitance to a second capacitor and generate the second capacitive sensor reading.

4. The directional capacitive proximity sensing circuit as set forth in claim 1, wherein the output circuitry is further configured to produce the output signal to indicate detection of the user proximate to the mobile device in a location generally above the directional capacitive proximity sensing circuit when the sensed first capacitance is equal to the sensed second capacitance.

5. The directional capacitive proximity sensing circuit as set forth in claim 1, wherein the first capacitance is indicative of the proximity of the user with respect to the first capacitive sensor.

6. The directional capacitive proximity sensing circuit as set forth in claim 1, wherein the second capacitance is indicative of the proximity of the user with respect to the second capacitive sensor.

9. The directional capacitive proximity sensing circuit as set forth in claim 1, wherein the one or more guard electrodes comprises a first guard electrode having the first capacitive sensor capacitively coupled to a first section of the first guard electrode, and the second capacitive sensor capacitively coupled to a second section of the first guard electrode adjacent the first section of the first guard electrode.

24. The directional capacitive proximity sensing circuit as set forth in claim 1, wherein the mobile device comprises a display screen, wherein the display screen is configured to be deactivated when the output signal indicates detection of the user proximate to a location generally above the directional capacitive proximity sensing circuit.

7. A directional capacitive proximity sensing circuit comprising:

one or more guard electrodes;

first capacitive sensor circuitry operable to sense a first capacitance and produce a first capacitive sensor reading indicative of the sensed first capacitance, wherein the first capacitive sensor circuitry includes a first capacitive sensor coupled to a first section of at least one of the one or more guard electrodes; and

second capacitive sensor circuitry operable to sense a second capacitance and produce a second capacitive sensor reading indicative of the sensed second capacitance, wherein the second capacitive sensor circuitry includes a second capacitive sensor coupled to a second section of at least one of the one or more guard electrodes,

wherein the one or more guard electrodes are controlled with a low impedance output to one or more voltages.

8. The directional capacitive proximity sensing circuit as set forth in claim 7, wherein the one or more guard electrodes are coupled to a first voltage in a first phase, and are coupled to a second voltage in a second phase.

10. A directional capacitive proximity sensing circuit comprising:

one or more guard electrodes;

first capacitive sensor circuitry operable to sense a first capacitance and produce a first capacitive sensor reading indicative of the sensed first capacitance, wherein the first capacitive sensor circuitry includes a first capacitive sensor coupled to a first section of at least one of the one or more guard electrodes; and

second capacitive sensor circuitry operable to sense a second capacitance and produce a second capacitive sensor reading indicative of the sensed second capacitance, wherein the second capacitive sensor circuitry includes a second capacitive sensor coupled to a second section of at least one of the one or more guard electrodes,

wherein the one or more guard electrodes comprises a first guard electrode having the first capacitive sensor coupled to a first section of the first guard electrode, and a second guard electrode having the second capacitive sensor coupled to a second section of the second guard electrode, and

wherein the first guard electrode is disposed in a device at a first location near a first component of the device, and the second guard electrode is disposed in the device at a second location adjacent the first location and near a second component of the device.

11. A directional capacitive proximity sensing circuit comprising:

one or more guard electrodes;

first capacitive sensor circuitry operable to sense a first capacitance and produce a first capacitive sensor reading indicative of the sensed first capacitance, wherein the first capacitive sensor circuitry includes a first capacitive sensor coupled to a first section of at least one of the one or more guard electrodes; and

second capacitive sensor circuitry operable to sense a second capacitance and produce a second capacitive sensor reading indicative of the sensed second capacitance, wherein the second capacitive sensor circuitry includes a second capacitive sensor coupled to a second section of at least one of the one or more guard electrodes,

wherein the first section of the at least one of the one or more guard electrodes is disposed near a first component of a device and the second section of the at least one of the one or more guard electrodes is disposed adjacent the first section of the at least one of the one or more guard electrodes and near a second component of the device.

12. The directional capacitive proximity sensing circuit as set forth in claim 11, wherein the device comprises a mobile phone, the first component comprises a top surface of the phone, and the second component comprises a display screen.

13. A directional capacitive proximity sensing circuit for use with a mobile device, comprising:

a guard electrode;

a first sensor coupled to a first section of the guard electrode;

a second sensor coupled to a second section of the guard electrode adjacent the first section of the guard electrode;

first capacitive sensor circuitry coupled to the first sensor, the first capacitive sensor circuitry operable to sense user proximity to the mobile device with respect to the first sensor and to produce a first capacitive sensor reading responsive to the sensed user proximity with respect to the first sensor and indicative of the user proximate to the first sensor;

second capacitive sensor circuitry coupled to the second sensor, the second capacitive sensor circuitry operable to sense user proximity to the mobile device with respect to the second sensor and to produce a second capacitive sensor reading responsive to the sensed user proximity with respect to the second sensor and indicative of the user proximate to the second sensor; and

output circuitry operable to receive and compare the first and second capacitive sensor readings and produce an output signal to indicate detection of the user proximate to the mobile device in a location nearer the first sensor than the second sensor when the first capacitive sensor reading is different than the second capacitive sensor reading.

14. The directional capacitive proximity sensing circuit as set forth in claim 13, wherein the output circuitry is further configured to produce the output signal to indicate detection of the user proximate to the mobile device in a location generally above the directional capacitive proximity sensing circuit when the first capacitive sensor reading is equal to the second capacitive sensor reading.

15. The directional capacitive proximity sensing circuit as set forth in claim 13, wherein the first capacitive sensor circuitry comprises a first switched integrator circuit operable during a first phase to apply a voltage to the first sensor, and operable during a second phase to transfer a first capacitance sensed between the user and the first sensor to a first capacitor and generate the first capacitive sensor reading.

16. The directional capacitive proximity sensing circuit as set forth in claim 13, wherein the second capacitive sensor circuitry comprises a second switched integrator circuit operable during a first phase to apply a voltage to the second sensor, and operable during a second phase to transfer a second capacitance sensed between the user and the second sensor to a second capacitor and generate the second capacitive sensor reading.

25. The directional capacitive proximity sensing circuit as set forth in claim 13, wherein the mobile device comprises a display screen, wherein the display screen is configured to be deactivated when the output signal indicates detection of the user proximate to the mobile device in the location generally above the directional capacitive proximity sensing circuit.

26. The directional capacitive proximity sensing circuit as set forth in claim 13, wherein the first sensor comprises a first sensor plate capacitively coupled to the first section of the guard electrode, and the second sensor comprises a second sensor plate capacitively coupled to the second section of the guard electrode.

27. The directional capacitive proximity sensing circuit as set forth in claim 13, wherein the guard electrode is coupled to a first voltage during a first phase, and is coupled to a second voltage during a second phase.

17. An integrated circuit operable to detect a general direction of user proximity with respect to the integrated circuit, the integrated circuit comprising:

a first switched capacitive integrator circuit including a first sensor plate, the first switched capacitive integrator circuit operable to sense a first capacitance and produce a first output signal in response to the sensed first capacitance;

a second switched capacitive integrator circuit including a second sensor plate located adjacent the first sensor plate, the second switched capacitive integrator circuit operable to sense a second capacitance and produce a second output signal in response to the sensed second capacitance;

one or more capacitive plates, wherein at least one of the one or more capacitive plates has a first section coupled to the first sensor plate, and at least one of the one or more capacitive plates has a second section coupled to the second sensor plate; and

output circuitry operable to receive the first output signal and second output signal, and to produce a third output signal operable to indicate detection of the user proximity with respect to at least one of the first sensor plate or the second sensor plate.

18. The integrated circuit as set forth in claim 17, wherein the first switched capacitive integrator circuit is operable during a first phase to apply a voltage to the first sensor plate, and operable during a second phase to transfer the first capacitance to a first capacitor and generate the first output signal.

19. The integrated circuit as set forth in claim 17, wherein the second switched capacitive integrator circuit is operable during a first phase to apply a voltage to the second sensor plate, and operable during a second phase to transfer the second capacitance to a second capacitor and generate the second output signal.

20. The integrated circuit as set forth in claim 17, wherein the one or more capacitive plates comprises a first capacitive plate having the first sensor plate coupled to a first section of the first capacitive plate, and the second sensor plate coupled to a second section of the first capacitive plate.

21. The integrated circuit as set forth in claim 17, wherein the one or more capacitive plates comprises a first capacitive plate having the first sensor plate coupled to a first section of the first capacitive plate, and a second capacitive plate having the second sensor plate coupled to a second section of the second capacitive plate.

22. The integrated circuit as set forth in claim 17, wherein the third output signal indicates detection of the user proximity in a location nearer the first sensor plate than the second sensor plate when the user proximity indicated by the first output signal is different than the user proximity indicated by the second output signal.

23. The integrated circuit as set forth in claim 17, wherein the third output signal indicates detection of user proximity in a location generally above the integrated circuit when the user proximity indicated by the first output signal is equal to the user proximity indicated by the second output signal.

28. The integrated circuit as set forth in claim 17, wherein the mobile device comprises a display screen, wherein the display screen is configured to be deactivated when the output signal indicates detection of the user proximity in the location generally above the directional capacitive proximity sensing circuit.

29. The integrated circuit as set forth in claim 17, wherein the one or more capacitive plates are coupled to a first voltage during a first phase, and are coupled to a second voltage during a second phase.