Method and device for improved accuracy of proximity and touch detection in mobile devices

• US 10,282,028 B2
• Filed: 01/10/2017
• Issued: 05/07/2019
• Est. Priority Date: 10/31/2014
• Status: Active Grant

• Current Assignee: Semtech Corporation
• Original Assignee: Semtech Corporation
• Inventors: Rouaissia, Chaouki, Ott, III, Jerald G.
• Primary Examiner(s): Nguyen, Jennifer T
• Application Number:
  US15/402,642
• Publication Number:
  US 20170147145A1
• Time in Patent Office: 847 Days
• Field of Search: 345174
• CPC Class Codes: G06F 2203/04101 2.5D-digitiser, i.e. digitiser detecting the X/Y position of the input means, finger or stylus, also when it does not touch, but is proximate to the digitiser's interaction surface and also measures the distance of the input means within a short range in the Z direction, possibly with a separate measurement setup
• CPC Class Codes: G06F 2203/04103 Manufacturing, i.e. details related to manufacturing processes specially suited for touch sensitive devices
• CPC Class Codes: G06F 2203/04107 Shielding in digitiser, i.e. guard or shielding arrangements, mostly for capacitive touchscreens, e.g. driven shields, driven grounds
• CPC Class Codes: G06F 2203/04108 Touchless 2D- digitiser, i.e. digitiser detecting the X/Y position of the input means, finger or stylus, also when it does not touch, but is proximate to the digitiser's interaction surface without distance measurement in the Z direction
• CPC Class Codes: G06F 3/04182 Filtering of noise external to the device and not generated by digitiser components
• CPC Class Codes: G06F 3/0443 using a single layer of sensing electrodes
• CPC Class Codes: H03K 17/955 using a capacitive detector
• CPC Class Codes: H03K 2217/94015 Mechanical, e.g. by displacement of a body, a shielding element, or a magnet, in or out of the sensing area
• CPC Class Codes: H03K 2217/94031 Calibration involving digital processing
• CPC Class Codes: H03K 2217/960705 Safety of capacitive touch and proximity switches, e.g. increasing reliability, fail-safe
• CPC Class Codes: H04M 1/0266 for a display module assembly

Abstract

A mobile device has a proximity sensor. A compensation value of the proximity sensor is determined. The compensation value is compared to a reference compensation value to determine validity of the compensation value. A capacitance of the proximity sensor is measured. A value of the capacitance of the proximity sensor is adjusted based on the compensation value. A coefficient defining a relationship between a capacitance of the proximity sensor and a temperature of the mobile device is calculated. A temperature sensor is coupled to the proximity sensor. The temperature of the mobile device is measured. A value of the capacitance of the proximity sensor is adjusted based on the coefficient and the temperature of the mobile device. The adjusted capacitance value is compared to a threshold capacitance value to determine proximity of an object to the mobile device. A radio frequency signal is adjusted by detecting proximity.

Claims

1. A method of detecting proximity, comprising:

providing a proximity sensor;

coupling a capacitive sensing element to the proximity sensor;

determining a reference compensation value for the proximity sensor;

storing the reference compensation value in a read-only memory of the proximity sensor;

determining a compensation value of the proximity sensor after determining the reference compensation value;

comparing the compensation value to the reference compensation value to determine validity of the compensation value; and

measuring a self-capacitance of the capacitive sensing element with the proximity sensor using the compensation value as an offset.

2. The method of claim 1, further including manufacturing, by a manufacturer, a mobile device including the proximity sensor, wherein the manufacturer determines the reference compensation value of the proximity sensor in the mobile device.

3. The method of claim 2, further including determining the compensation value of the proximity sensor during use of the proximity sensor by an end user.

4. The method of claim 1, further including:

providing a temperature sensor coupled to the proximity sensor; and

adjusting the self-capacitance measurement based on a reading of the temperature sensor.

5. The method of claim 4, further including:

manufacturing a mobile device including the proximity sensor and temperature sensor; and

calculating a coefficient defining a relationship between a capacitance of the proximity sensor and a temperature of the mobile device while manufacturing the mobile device.

6. The method of claim 1, further including using the compensation value as an offset by:

providing a bank of capacitors; and

adjusting the bank of capacitors based on the compensation value.

7. A method of detecting proximity, comprising:

manufacturing, by a manufacturer, a mobile device including a proximity sensor;

determining, by the manufacturer, a reference compensation value for the proximity sensor in the mobile device;

determining, by the mobile device during use of the mobile device by an end user, a compensation value of the proximity sensor;

determining validity of the compensation value by comparing the compensation value to the reference compensation value; and

detecting proximity using the proximity sensor with the compensation value as an offset.

8. The method of claim 7, further including:

manufacturing a mobile device including the proximity sensor; and

determining the reference compensation value while manufacturing the mobile device.

9. The method of claim 7, further including providing the proximity sensor including a bank of capacitors, wherein the proximity sensor uses the compensation value as an offset by adjusting the bank of capacitors based on the compensation value.

10. The method of claim 7, further including detecting proximity by configuring the proximity sensor to generate a voltage potential proportional to a self-capacitance measured at a terminal of the proximity sensor.

11. The method of claim 10, further including:

coupling a sensing element to the proximity sensor; and

configuring the proximity sensor to generate the voltage potential proportional to the self-capacitance, wherein the self-capacitance is a self-capacitance of the sensing element.

12. The method of claim 10, further including coupling the voltage potential to an input terminal of an analog-to-digital converter.

13. The method of claim 12, further including comparing a digital output of the analog-to-digital converter to a proximity threshold to determine proximity.

14. A method of detecting proximity, comprising:

providing a proximity sensor;

determining a compensation value of the proximity sensor;

determining validity of the compensation value by comparing the compensation value to a reference compensation value; and

adjusting a voltage potential of the proximity sensor proportionally to the compensation value.

15. The method of claim 14, wherein adjusting the voltage potential of the proximity sensor includes:

providing a bank of capacitors; and

adjusting the bank of capacitors based on the compensation value.

16. The method of claim 14, further including coupling the voltage potential to an analog-to-digital converter to generate a digital representation of the voltage potential.

17. The method of claim 16, further including adjusting the digital representation based on a temperature measured by the proximity sensor.

18. The method of claim 14, further including:

manufacturing a mobile device including the proximity sensor; and

determining the reference compensation value while manufacturing the mobile device.

19. The method of claim 14, further including storing the reference compensation value in a read-only memory of the proximity sensor.

20. A proximity sensor, comprising:

a reference compensation value of the proximity sensor;

a comparator for comparing a measured compensation value to the reference compensation value; and

an offset compensation configured to adjust a voltage potential of the proximity sensor based on the measured compensation value.

21. The proximity sensor of claim 20, further including a temperature sensor coupled to the proximity sensor.

22. The proximity sensor of claim 20, wherein the offset compensation includes a bank of capacitors controlled by the measured compensation value.

23. The proximity sensor of claim 20, further including an analog-to-digital converter coupled to an output of the offset compensation.

24. The proximity sensor of claim 23, further including a digital processor coupled to an output of the analog-to-digital converter.