Barrier Electrode Driven By An Excitation Signal

Abstract

Apparatuses and method of driving a shield electrode and electrodes of a matrix are described. One apparatus includes a plurality of electrodes disposed as a matrix below a touch surface, a shield electrode, and a capacitance-sensing circuit. The capacitance-sensing circuit measures capacitances of the plurality of electrodes to detect a conductive object in contact with the touch surface or above the touch surface. The capacitance-sensing circuit measures a self-capacitance of a first electrode of the plurality of electrodes while driving the shield electrode with a shield signal, the shield signal being the same electrical potential as the plurality of electrodes. The capacitance-sensing circuit drives a second electrode of the plurality of electrodes as a barrier electrode to increase a detection distance from the touch surface to detect a conductive object above the touch surface.

1 - 20 . (canceled) 
     
     
         21 . An apparatus comprising:
 a plurality of electrodes disposed as a matrix below a touch surface;   a shield electrode; and   a capacitance-sensing circuit to measure capacitances of the plurality of electrodes to detect a conductive object in contact with the touch surface or above the touch surface, wherein the capacitance-sensing circuit is configured to measure a self-capacitance of a first electrode of the plurality of electrodes while driving the shield electrode with a shield signal, the shield signal being the same electrical potential as the plurality of electrodes, and wherein the capacitance-sensing circuit is further configured to drive a second electrode of the plurality of electrodes as a barrier electrode to increase a detection distance from the touch surface to detect a conductive object above the touch surface.   
     
     
         22 . The apparatus of  claim 21 , wherein the capacitance-sensing circuit comprises:
 a sensing channel to selectively couple to one or more of the plurality of electrodes; and   an analog-to-digital converter (ADC) coupled to the sensing channel, the ADC to convert the capacitances to digital values.   
     
     
         23 . The apparatus of  claim 22 , further comprising
 processing logic coupled to the ADC, the processing logic to detect a proximity event of a conductive object based on the digital values.   
     
     
         24 . The apparatus of  claim 21 , wherein the capacitance-sensing circuit further comprises:
 a signal source to provide the shield signal; and   a signal generator to generate an excitation signal, wherein the capacitance-sensing circuit is further configured to drive the second electrode as the barrier electrode with the excitation signal.   
     
     
         25 . The apparatus of  claim 24 , wherein the shield signal is synchronized to the excitation signal. 
     
     
         26 . The apparatus of  claim 24 , wherein the shield signal is less than 5 volts and the excitation signal is greater than 5 volts. 
     
     
         27 . The apparatus of  claim 22 , wherein the capacitance-sensing circuit further comprises:
 a signal source to provide the shield signal;   a signal generator to generate an excitation signal; and   a multiplexer coupled to the plurality of electrodes, the signal generator, the signal source, and the sensing channel.   
     
     
         28 . The apparatus of  claim 21 , wherein the plurality of electrodes form a touch area, and wherein the barrier electrode is a first edge electrode within the touch area. 
     
     
         29 . The apparatus of  claim 21 , wherein the plurality of electrodes form a touch area, wherein the capacitance-sensing circuit is further configured to drive two of the plurality of electrodes as a first barrier electrode and a second barrier electrode, 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. 
     
     
         30 . The apparatus of  claim 21 , wherein the capacitance-sensing circuit is configured to measure the self-capacitance of the first electrode in a self-capacitance mode, and wherein the capacitance-sensing circuit is configured to measure a mutual capacitance between at least two of the plurality of electrodes in a mutual capacitance mode. 
     
     
         31 . The apparatus of  claim 30 , further comprising
 processing logic coupled to the ADC, the processing logic to detect a proximity event of a conductive object in the self-capacitance mode and to detect a touch event of one or more conductive objects on the touch surface in the mutual capacitance mode.   
     
     
         32 . A method comprising:
 measuring a self-capacitance of a first electrode of a plurality of electrodes of a matrix disposed below a touch surface to detect a conductive object in contact with the touch surface or above the touch surface;   while measuring the self-capacitance of the first electrode, driving a shield electrode with a shield signal, the shield signal being the same electrical potential as the plurality of electrodes; and   driving a second electrode of the plurality of electrodes as a barrier electrode to increase a detection distance from the touch surface to detect a conductive object above the touch surface.   
     
     
         33 . The method of  claim 32 , further comprising converting the capacitances to digital values using a an analog-to-digital converter (ADC). 
     
     
         34 . The method of  claim 33 , further comprising detecting a proximity event of a conductive object based on the digital values. 
     
     
         35 . The method of  claim 32 , wherein the driving the second electrode as the barrier electrode comprises driving the second electrode with an excitation signal that is synchronized with the shield signal, the excitation signal being greater than the shield signal. 
     
     
         36 . The method of  claim 31 , further comprising measuring a mutual capacitance between at least two of the plurality of electrodes in a mutual capacitance mode, and wherein the self-capacitance is measured in a self-capacitance mode. 
     
     
         37 . A processing device comprising:
 a capacitance-sensing circuit;   a first pin coupled to a shield signal source;   a plurality of pins coupled to the capacitance-sensing circuit, wherein the capacitance-sensing circuit is configured to measure a self-capacitance of a second pin of the plurality of pins while driving the first pin with a shield signal, the shield signal being the same electrical potential as the plurality of pins, and wherein the capacitance-sensing circuit is further configured to drive a third pin of the plurality of pins with an excitation signal; and   processing logic to detect a proximity event of a conductive object based on the self-capacitance, wherein the excitation signal increase a detection distance for detecting the proximity event.   
     
     
         38 . The processing device of  claim 37 , wherein the capacitance-sensing circuit comprises:
 a sensing channel to selectively couple to one or more of the plurality of pins; and   an analog-to-digital converter (ADC) coupled to the sensing channel, the ADC to convert the self-capacitance to a digital value.   
     
     
         39 . The processing device of  claim 37 , wherein the capacitance-sensing circuit further comprises:
 a signal source to provide the shield signal; and   a signal generator to generate the excitation signal.   
     
     
         40 . The processing device of  claim 37 , wherein the shield signal is less than 5 volts and the excitation signal is greater than 5 volts.