Barrier electrode driven by an excitation signal

1. An apparatus comprising a capacitance-sensing circuit coupled to a capacitive-sense array comprising a plurality of electrodes, wherein the capacitance-sensing circuit comprises a plurality of sensing channels and is operative to:

measure signals on a first subset of the plurality of electrodes using the plurality of sensing channels, wherein each of the plurality of sensing channels is coupled to one of the first subset of the plurality of electrodes;

drive a first barrier electrode of the plurality of electrodes with an excitation signal while measuring the signals on the first subset, wherein the excitation signal is greater in magnitude than the measured signals, and wherein the first barrier electrode is adjacent to an edge electrode of the first subset of the plurality of electrodes coupled to one of the plurality of sensing channels;

drive a second barrier electrode of the plurality of electrodes with the excitation signal while measuring the signals on the first subset, wherein the second barrier electrode is adjacent to another edge electrode of the first subset of the plurality of electrodes coupled to another one of the plurality of sensing channels;

drive a second subset of the plurality of electrodes with a shield signal while measuring the signals on the first subset,

wherein the excitation signal is greater in magnitude than the shield signal,

wherein the plurality of electrodes of the capacitive-sense array comprises a plurality of row electrodes and a plurality of column electrodes, and

wherein the first barrier electrode is a first column electrode of the plurality of column electrodes, the second barrier electrode is a second column electrode of the plurality of column electrodes, and the first subset includes column electrodes of the plurality of column electrodes, the column electrodes being between the first column electrode and the second column electrode.

2. The apparatus of claim 1 , wherein the capacitance-sensing circuit is further operative to convert the measured signals to digital values representing self-capacitance measurements of the first subset, and wherein the apparatus further comprises processing logic coupled to the capacitance-sensing circuit, wherein the processing logic is operative to detect a proximity event of a conductive object based on the digital values, wherein the barrier electrode driven by the excitation signal increases a detection distance of the apparatus.

3. The apparatus of claim 1 , wherein the shield signal is synchronized with the excitation signal.

4. The apparatus of claim 1 , wherein the plurality of sensing channels comprises three or more sensing channels, wherein the three or more sensing channels measure the signals on three or more of the first subset of the plurality of electrodes, wherein the measured signal from the respective electrode is representative of a self-capacitance of the respective electrode.

5. The apparatus of claim 1 , wherein the capacitance-sensing circuit is further to: drive a transmit signal on a first electrode of the second subset of the plurality of electrodes; and measure a receive signal on a second electrode of the first subset of the plurality of electrodes using one of the plurality of sensing channels, wherein the receive signal is representative of a mutual capacitance between the first electrode and the second electrode.

6. The apparatus of claim 1 , wherein at least one of the plurality of sensing channels comprises:

an integrator capacitor;

a switch; and

an operational amplifier, and wherein the capacitance-sensing circuit further comprises:

a signal generator to generate the excitation signal;

an analog-to-digital converter (ADC); and

processing logic.

7. A method comprising:

coupling a plurality of receive channels of a capacitance-sensing circuit to a first subset of a plurality of electrodes of a capacitive-sense array;

measuring signals on the first subset by the capacitance-sensing circuit;

driving a barrier electrode of the plurality of electrodes with an excitation signal while measuring the signals on the first subset, wherein the excitation signal is greater in magnitude than the signals measured on the first subset, wherein the barrier electrode is adjacent to an edge electrode of the first subset of the plurality of electrodes coupled to one of the plurality of receive channels;

driving a second subset of the plurality of electrodes with a shield signal while measuring the signals on the first subset, wherein the execution signal is greater in magnitude than the shield signal;

driving a transmit signal on a first electrode of a second subset of the plurality of electrodes; and

measuring a receive signal on a second electrode of the first subset of the plurality of electrodes using one of the plurality of sensing channels, wherein the receive signal is representative of a mutual capacitance between the first electrode and the second electrode.

8. The method of claim 7 , further comprising:

converting the measured signals to digital values representing self-capacitance measurements of the first subset; and

detecting a proximity event of a conductive object based on the digital values, wherein the barrier electrode driven by the excitation signal increases a detection distance of the capacitance-sensing circuit.

9. An apparatus comprising:

a capacitive-sense array of a plurality of electrodes; and

a processing device coupled to the capacitive-sense array, wherein the processing device is configured to:

selectively couple sensing channels of a capacitance-sensing circuit to a first subset of the plurality of electrodes;

selectively couple a shield signal to a second subset of the plurality of electrodes; and

selectively couple an excitation signal to a third subset of the plurality of electrodes, wherein the third subset includes a first barrier electrode that is adjacent to an edge electrode of the first subset;

measure signals from the first subset by the sensing channels at a first phase;

drive the second subset with the shield signal while measuring the signals on the first subset; and

drive the third subset with the excitation signal while measuring the signals on the first subset, wherein the excitation signal is greater in magnitude than the shield signal;

selectively couple an excitation signal to a fourth subset of the plurality of electrodes, wherein the fourth subset includes a second barrier electrode that adjacent to an edge electrode of the first subset;

measure signals from the first subset by the sensing channels at a second phase;

drive the second subset with the shield signal while measuring the signals on the first subset; and

drive the fourth subset with the excitation signal while measuring the signals on the first subset, wherein the excitation signal is greater in magnitude than the shield signal,

wherein the plurality of electrodes of the capacitive-sense array comprises a plurality of row electrodes and a plurality of column electrodes, wherein the first barrier electrode is a first column electrode of the plurality of column electrodes, the second barrier electrode is a second column electrode of the plurality of column electrodes, and the first subset includes column electrodes of the plurality of column electrodes, the column electrodes being between the first column electrode and the second column electrode.

10. The apparatus of claim 9 , wherein the processing device comprises:

an analog-to-digital converter (ADC) coupled to one or more of the sensing channels, the ADC to convert the measured signal to digital values representing self-capacitance measurements of the first subset; and

processing logic coupled to the ADC, the processing logic to detect a proximity event of a conductive object based on the digital values, wherein the third subset driven by the excitation signal increases a detection distance of the processing device.

11. The apparatus of claim 9 , wherein the processing device further comprises a signal generator to generate the excitation signal, wherein the shield signal is synchronized to the excitation signal.

12. The apparatus of claim 11 , wherein the shield signal is less than 5 volts and the excitation signal is greater than 5 volts.

13. The apparatus of claim 9 , wherein the processing device further comprises:

a signal generator to generate the excitation signal;

a signal source to provide the shield signal; and

a multiplexer coupled to the plurality of electrodes, the signal generator, the signal source, and the sensing channels, wherein the multiplexer selectively couples the sensing channels to the first subset, the signal source to the second subset, and the signal generator to the third and fourth subset in a first configuration, and wherein the multiplexer selectively couples the sensing channels to a fifth subset of the plurality of electrodes, the signal source to a sixth subset of the plurality of electrodes, and the signal generator to a seventh subset of the plurality of electrodes in a second configuration, wherein the seventh subset includes barrier electrodes that are adjacent to edge electrodes of the fifth subset, and

wherein the processing device, while in the second configuration,

measures additional signals from the fifth subset by the sensing channels,

drives the fifth subset with the shield signal while measuring the additional signals on the fifth subset, and

drives the sixth subset with the excitation signal while measuring the additional signals on the fifth subset.

14. An apparatus comprising a capacitance-sensing circuit coupled to a capacitive-sense array comprising a plurality of electrodes, wherein the capacitance-sensing circuit comprises a plurality of sensing channels and is operative to:

measure signals on a first subset of the plurality of electrodes using the plurality of sensing channels, wherein each of the plurality of sensing channels is coupled to one of the first subset of the plurality of electrodes;

drive a first barrier electrode of the plurality of electrodes with an excitation signal while measuring the signals on the first subset, wherein the excitation signal is greater in magnitude than the measured signals, and wherein the first barrier electrode is adjacent to an edge electrode of the first subset of the plurality of electrodes coupled to one of the plurality of sensing channels;

drive a second barrier electrode of the plurality of electrodes with the excitation signal while measuring the signals on the first subset, wherein the second barrier electrode is adjacent to another edge electrode of the first subset of the plurality of electrodes coupled to another one of the plurality of sensing channels;

drive a second subset of the plurality of electrodes with a shield signal while measuring the signals on the first subset,

wherein the excitation signal is greater in magnitude than the shield signal,

wherein the plurality of electrodes of the capacitance sense array comprises a plurality of row electrodes and a plurality of column electrodes, wherein the first barrier electrode is a first row electrode of the plurality of row electrodes, the second barrier is a second row electrode of the plurality of row electrodes, and the first subset includes row electrodes of the plurality of row electrodes, the row electrodes being between the first row electrode and the second row electrode.

15. The apparatus of claim 14 , further comprising the capacitive-sense array, wherein the capacitive-sense array, wherein the plurality of electrodes form a touch area, and wherein the first barrier electrode is a first edge electrode within the touch area and the second barrier electrode is a second edge electrode within the touch area.