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

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.