METHODS AND APPARATUS FOR A TOUCH SENSOR

1 . A sensing circuit configured to connect to a touch sensor, comprising:

an amplifier configured to receive an input signal from the touch sensor and transform the input signal to a voltage signal;

an analog-to-digital converter connected to the amplifier and configured to convert the voltage signal to a digital value;

a first detection circuit configured to determine a touch event according to the digital value and a first criteria; and

a second detection circuit configured to determine the touch event according to the digital value and a second criteria.

2 . The sensing circuit of claim 1 , wherein the first criteria comprises a predetermined first threshold value.

3 . The sensing circuit of claim 2 , wherein the first detection circuit is configured to compare the digital value to the first threshold value.

4 . The sensing circuit of claim 3 , wherein the first detection circuit generates an ON signal if the digital value is greater than the first threshold value.

5 . The sensing circuit of claim 1 , wherein the second criteria comprises a peak value that is equal to the digital value with the highest magnitude.

6 . The sensing circuit of claim 5 , wherein the second criteria comprises a secondary value that is less than the peak value.

7 . The sensing circuit of claim 6 , wherein the second detection circuit is configured to compare the digital value to at least one of the peak value and the secondary value.

8 . The sensing circuit of claim 7 , wherein the second detection circuit generates an ON signal if the digital value is greater than the secondary value and less than or equal to the peak value.

9 . A method of improving touch detection in a capacitive touch sensor, comprising:

receiving a plurality of signals from the touch sensor;

generating a plurality of digital values comprising:

transforming each signal to a voltage signal; and

converting each voltage signal to digital value;

comparing each digital value to a first threshold value;

comparing each digital value to at least a second value and a third value;

identifying one digital value, from the plurality of digital values, that corresponds to an actual touch based on the comparisons to:

the first threshold value;

the second value; and

the third value; and

identifying at least one digital value, from the plurality of digital values, that corresponds to cross talk based on the comparisons to:

the first threshold value;

the second value; and

the third value.

10 . The method of claim 9 , wherein the second value is equal to the digital value with the highest magnitude.

11 . The method of claim 10 , wherein the third value is less than the second value.

12 . The method of claim 9 , further comprising comparing each digital value to a fourth value that less than the digital value with the highest magnitude.

13 . The method of claim 9 , wherein identifying one digital value that corresponds to the actual touch comprises:

determining if the digital value is greater than the first threshold;

determining if the digital value is greater than the third value; and

determining if the digital value is less than or equal to the second value.

14 . The method of claim 9 , wherein identifying at least one digital value that corresponds to cross talk comprises:

determining if the at least one digital value is greater than the first threshold; and

determining if the at least one digital value is less than the third value.

15 . A system, comprising:

a touch pad comprising a plurality of capacitive touch sensors, each capacitive touch sensor configured to generate a sensor signal;

a sensing circuit connected to the touch sensor and comprising:

an amplifier connected to the touch sensor and configured to transform each sensor signal to a voltage signal;

an analog-digital converter (ADC) connected to the amplifier and configured to convert each voltage signal to a digital value; and

a detection circuit connected to the ADC and configured to:

compare each digital value to a minimum threshold value;

compare each digital value to a set of secondary values; and

generate one of a first signal and a second signal for each digital value according to the comparisons to the minimum threshold value and the set of second values; and

a processing circuit responsive to the sensing circuit.

16 . The system of claim 15 , further comprising comparing each digital value to a maximum threshold value.

17 . The system of claim 15 , wherein the detection circuit generates the first signal if the digital value is greater than the minimum threshold value and less than the maximum threshold value.

18 . The system of claim 15 , wherein the set of second values comprises a peak value that is equal to the digital value that has the highest magnitude of the digital values that are less than the maximum threshold.

19 . The system of claim 18 , wherein the set of secondary values further comprises a second value that is less than the peak value.

20 . The system of claim 19 , wherein the detection circuit generates the second signal if the digital value is:

less than the second value; or

greater than the maximum threshold value.