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

• US 9,582,111 B2
• Filed: 10/31/2014
• Issued: 02/28/2017
• Est. Priority Date: 10/31/2014
• Status: Active Grant

• Current Assignee: Semtech Corporation
• Original Assignee: Semtech Corporation
• Inventors: Rouaissia, Chaouki, Ott, Jerald G. III
• Primary Examiner(s): NGUYEN, JENNIFER T
• Application Number:
  US14/530,112
• Publication Number:
  US 20160124573A1
• Time in Patent Office: 851 Days
• Field of Search: 345/174, 455/556.1, 455/556.2, 455/566, 455/77
• US Class Current: 1/1
• 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 mobile device including a proximity sensor;

coupling a capacitive sensing element to the proximity sensor;

determining a compensation value of the proximity sensor;

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

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

2. The method of claim 1, wherein adjusting the voltage potential of the proximity sensor includes adjusting a capacitance of the proximity sensor based on the compensation value.

3. The method of claim 1, further including:

coupling the voltage potential to an analog-to-digital converter to generate a digital representation of the voltage potential; and

adjusting the digital representation based on a temperature of the mobile device.

4. The method of claim 1, further including comparing the adjusted voltage potential to a threshold to determine proximity of an object to the mobile device.

5. The method of claim 1, further including calculating a coefficient defining a relationship between a capacitance of the proximity sensor and a temperature of the mobile device.

6. A method of detecting proximity, comprising:

providing a mobile device including 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 capacitor bank of the proximity sensor based on the compensation value after determining the compensation value is valid.

7. The method of claim 6, further including determining proximity of an object to the mobile device by measuring a capacitance of the proximity sensor.

8. The method of claim 6, further including adjusting a reading of the proximity sensor based on a temperature of the mobile device.

9. The method of claim 6, further including comparing the adjusted reading to a threshold to determine proximity of an object to the mobile device.

10. The method of claim 6, further including determining a coefficient defining a relationship between a capacitance of the proximity sensor and a temperature of the mobile device.

11. The method of claim 10, further including:

measuring the capacitance of the proximity sensor;

measuring the temperature of the mobile device; and

adjusting a value of the capacitance of the proximity sensor based on the coefficient and the temperature of the mobile device.

12. The method of claim 6, further including providing an analog-to-digital converter to generate a digital representation of the adjusted reading of the proximity sensor, wherein the adjusted reading of the proximity sensor is an analog voltage potential reduced based on the compensation value.

13. A method of detecting proximity, comprising:

providing a proximity sensor;

determining a reference compensation value of the proximity sensor;

comparing a first proximity reading to the reference compensation value to evaluate the first proximity reading as a valid compensation value or an invalid compensation value;

adjusting subsequent readings of the proximity sensor using the first proximity reading if the first proximity reading is a valid compensation value; and

comparing a second proximity reading to the reference compensation value to evaluate the second proximity reading as a valid compensation value or an invalid compensation value if the first proximity reading is an invalid compensation value.

14. The method of claim 13, wherein adjusting subsequent readings of the proximity sensor includes:

providing a bank of capacitors; and

adjusting the bank of capacitors based on the first proximity reading.

15. The method of claim 13, further including adjusting subsequent readings of the proximity sensor based on a temperature sensor.

16. The method of claim 13, further including adjusting a radio frequency signal based on the subsequent readings of the proximity sensor.

17. The method of claim 13, further including determining a coefficient defining a relationship between a capacitance of the proximity sensor and a temperature of the proximity sensor.

18. The method of claim 17, further including adjusting subsequent readings of the proximity sensor using the coefficient and the temperature of the proximity sensor.

19. 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;

an offset compensation configured to reduce a voltage potential of the proximity sensor based on the measured compensation value; and

an analog-to-digital converter including an input coupled to the voltage potential.

20. The proximity sensor of claim 19, further including a temperature sensor coupled to the proximity sensor.

21. The proximity sensor of claim 19, wherein the offset compensation further includes a bank of capacitors controlled by the measured compensation value.

22. The proximity sensor of claim 19, further including a digital processor coupled to an output of the analog-to-digital converter.