Patent Publication Number: US-10318086-B2

Title: Reducing touch sensor panel power consumption

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 15/068,426 (now U.S. Patent Application Publication No. 2016/0195959) entitled “REDUCING TOUCH SENSOR PANEL POWER CONSUMPTION,” filed Mar. 11, 2016, which is a continuation of U.S. patent application Ser. No. 14/090,174 (now U.S. Pat. No. 9,304,575) entitled “REDUCING TOUCH SENSOR PANEL POWER CONSUMPTION” filed Nov. 26, 2013, the entire disclosures of which are incorporated herein by reference for all purposes. 
    
    
     FIELD OF THE DISCLOSURE 
     This relates generally to touch sensing, and more particularly to reducing power consumption of a touch sensor panel. 
     BACKGROUND OF THE DISCLOSURE 
     Many types of input devices are presently available for performing operations in a computing system, such as buttons or keys, mice, trackballs, joysticks, touch sensor panels, touch screens and the like. Touch screens, in particular, are becoming increasingly popular because of their ease and versatility of operation as well as their declining price. Touch screens can include a touch sensor panel, which can be a clear panel with a touch-sensitive surface, and a display device such as a liquid crystal display (LCD) that can be positioned partially or fully behind the panel so that the touch-sensitive surface can cover at least a portion of the viewable area of the display device. 
     Touch screens can allow a user to perform various functions by touching the touch sensor panel using a finger, stylus or other object at a location often dictated by a user interface (UI) being displayed by the display device. In general, touch screens can recognize a touch and the position of the touch on the touch sensor panel, and the computing system can then interpret the touch in accordance with the display appearing at the time of the touch, and thereafter can perform one or more actions based on the touch. In the case of some touch sensing systems, a physical touch on the display is not needed to detect a touch. For example, in some capacitive-type touch sensing systems, fringing fields used to detect touch can extend beyond the surface of the display, and objects approaching the surface may be detected near the surface without actually touching the surface. 
     Capacitive touch sensor panels can be formed from a matrix of drive and sense lines of a substantially transparent conductive material, such as Indium Tin Oxide (ITO), often arranged in rows and columns in horizontal and vertical directions on a substantially transparent substrate. It is due in part to their substantial transparency that capacitive touch sensor panels can be overlaid on a display to form a touch screen, as described above. Some touch screens can be formed by integrating touch sensing circuitry into a display pixel stackup (i.e., the stacked material layers forming the display pixels). 
     Because such integrated touch screens can include one or more components that can provide functionality for both touch sensing and display operations, it can be useful to share the time that those components are used for those operations, and it can be useful to do so in a way that can reduce power consumption. 
     SUMMARY OF THE DISCLOSURE 
     The following description includes examples of reducing power consumption relating to touch sensing and display operations in a touch screen. In operation, some integrated touch screens can switch between a touch sensing phase, in which touch sensing can be performed, and a display phase, in which a displayed image can be updated. Touch sensing that is performed more frequently can provide for higher touch sensing accuracy. However, power can be consumed each time touch sensing is performed. Therefore, power consumption can be reduced if touch sensing is performed less frequently when higher touch accuracy is not needed or desired. The level of touch accuracy needed or desired can be based on an application or a UI that may be running or displayed on the touch screen. In some examples, fewer than all touch sensors on a touch screen can be utilized to reduce power consumed by the touch screen during a touch sensing phase. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  illustrates an example mobile telephone that includes a touch screen. 
         FIG. 1B  illustrates an example digital media player that includes a touch screen. 
         FIG. 1C  illustrates an example personal computer that includes a touch screen. 
         FIG. 2  is a block diagram of an example computing system that illustrates one implementation of an example touch screen according to examples of the disclosure. 
         FIG. 3  is a more detailed view of a touch screen showing an example configuration of drive lines and sense lines according to examples of the disclosure. 
         FIG. 4  illustrates an example configuration in which common electrodes (Vcom) can form portions of the touch sensing circuitry of a touch sensing system. 
         FIG. 5  is a three-dimensional illustration of an exploded view (expanded in the z-direction) of example display pixel stackups showing some of the elements within the pixel stackups of an example integrated touch screen. 
         FIG. 6  illustrates an example touch sensing operation according to examples of the disclosure. 
         FIG. 7  illustrates exemplary operation of a touch screen in two modes for reducing power consumption. 
         FIG. 8A  illustrates an exemplary circumstance in which the higher touch accuracy of active mode may not be needed or desired for proper touch screen operation. 
         FIG. 8B  illustrates an exemplary circumstance in which the touch accuracy of active mode may be needed or desired for some portion(s) of a touch screen while the touch accuracy of idle mode may be sufficient for other portion(s) of the touch screen. 
         FIG. 9  illustrates an exemplary process by which operation of a touch screen can be determined. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description of examples, reference is made to the accompanying drawings which form a part hereof, and in which it is shown by way of illustration specific examples that can be practiced. It is to be understood that other examples can be used and structural changes can be made without departing from the scope of the disclosed examples. 
     Some touch screens can be formed by integrating touch sensing circuitry into a display pixel stackup (i.e., the stacked material layers forming the display pixels). Because such integrated touch screens can include one or more components that can provide functionality for both touch sensing and display operations, it can be useful to share the time that those components are used for those operations, and it can be useful to do so in a way that can reduce power consumption. In operation, some integrated touch screens can switch between a touch sensing phase, in which touch sensing can be performed, and a display phase, in which a displayed image can be updated. Touch sensing that is performed more frequently can provide for higher touch sensing accuracy. However, power can be consumed each time touch sensing is performed. Therefore, power consumption can be reduced if touch sensing is performed less frequently when higher touch accuracy is not needed or desired. The level of touch accuracy needed or desired can be based on an application or a UI than may be running or displayed on the touch screen. 
       FIGS. 1A-1C  show example systems in which a touch screen according to examples of the disclosure may be implemented.  FIG. 1A  illustrates an example mobile telephone  136  that includes a touch screen  124 .  FIG. 1B  illustrates an example digital media player  140  that includes a touch screen  126 .  FIG. 1C  illustrates an example personal computer  144  that includes a touch screen  128 . Although not shown in the figures, the personal computer  144  can also be a tablet computer or a desktop computer with a touch-sensitive display. Touch screens  124 ,  126 , and  128  may be based on, for example, self capacitance or mutual capacitance, or another touch sensing technology. For example, in a self capacitance based touch system, an individual electrode with a self-capacitance to ground can be used to form a touch pixel (touch node) for detecting touch. As an object approaches the touch pixel, an additional capacitance to ground can be formed between the object and the touch pixel. The additional capacitance to ground can result in a net increase in the self-capacitance seen by the touch pixel. This increase in self-capacitance can be detected and measured by a touch sensing system to determine the positions of multiple objects when they touch the touch screen. A mutual capacitance based touch system can include, for example, drive regions and sense regions, such as drive lines and sense lines. For example, drive lines can be formed in rows while sense lines can be formed in columns (i.e., orthogonal). Touch pixels (touch nodes) can be formed at the intersections or adjacencies (in single layer configurations) of the rows and columns. During operation, the rows can be stimulated with an AC waveform and a mutual capacitance can be formed between the row and the column of the touch pixel. As an object approaches the touch pixel, some of the charge being coupled between the row and column of the touch pixel can instead be coupled onto the object. This reduction in charge coupling across the touch pixel can result in a net decrease in the mutual capacitance between the row and the column and a reduction in the AC waveform being coupled across the touch pixel. This reduction in the charge-coupled AC waveform can be detected and measured by the touch sensing system to determine the positions of multiple objects when they touch the touch screen. In some examples, a touch screen can be multi-touch, single touch, projection scan, full-imaging multi-touch, or any capacitive touch. 
       FIG. 2  is a block diagram of an example computing system  200  that illustrates one implementation of an example touch screen  220  according to examples of the disclosure. Computing system  200  could be included in, for example, mobile telephone  136 , digital media player  140 , personal computer  144 , or any mobile or non-mobile computing device that includes a touch screen. Computing system  200  can include a touch sensing system including one or more touch processors  202 , peripherals  204 , a touch controller  206 , and touch sensing circuitry (described in more detail below). Peripherals  204  can include, but are not limited to, random access memory (RAM) or other types of memory or storage, watchdog timers and the like. Touch controller  206  can include, but is not limited to, one or more sense channels  208 , channel scan logic  210  and driver logic  214 . Channel scan logic  210  can access RAM  212 , autonomously read data from the sense channels and provide control for the sense channels. In addition, channel scan logic  210  can control driver logic  214  to generate stimulation signals  216  at various frequencies and/or phases that can be selectively applied to drive regions of the touch sensing circuitry of touch screen  220 , as described in more detail below. In some examples, touch controller  206 , touch processor  202  and peripherals  204  can be integrated into a single application specific integrated circuit (ASIC). 
     It should be apparent that the architecture shown in  FIG. 2  is only one example architecture of system  200 , and that the system could have more or fewer components than shown, or a different configuration of components. The various components shown in  FIG. 2  can be implemented in hardware, software, firmware or any combination thereof, including one or more signal processing and/or application specific integrated circuits. 
     Computing system  200  can include a host processor  228  for receiving outputs from touch processor  202  and performing actions based on the outputs. For example, host processor  228  can be connected to program storage  232  and a display controller, such as a Liquid-Crystal Display (LCD) driver  234 . It is understood that although the examples of the disclosure are described with reference to LCD displays, the scope of the disclosure is not so limited and can extend to other types of displays, such as Light-Emitting Diode (LED) displays, including Active-Matrix Organic LED (AMOLED) and Passive-Matrix Organic LED (PMOLED) displays. 
     Host processor  228  can use LCD driver  234  to generate an image on touch screen  220 , such as an image of a user interface (UI), and can use touch processor  202  and touch controller  206  to detect a touch on or near touch screen  220 , such as a touch input to the displayed UI. The touch input can be used by computer programs stored in program storage  232  to perform actions that can include, but are not limited to, moving an object such as a cursor or pointer, scrolling or panning, adjusting control settings, opening a file or document, viewing a menu, making a selection, executing instructions, operating a peripheral device connected to the host device, answering a telephone call, placing a telephone call, terminating a telephone call, changing the volume or audio settings, storing information related to telephone communications such as addresses, frequently dialed numbers, received calls, missed calls, logging onto a computer or a computer network, permitting authorized individuals access to restricted areas of the computer or computer network, loading a user profile associated with a user&#39;s preferred arrangement of the computer desktop, permitting access to web content, launching a particular program, encrypting or decoding a message, and/or the like. Host processor  228  can also perform additional functions that may not be related to touch processing. 
     In some examples, RAM  212 , program storage  232 , or both, can be non-transitory computer readable storage media. One or both of RAM  212  and program storage  232  can have stored therein instructions, which when executed by touch processor  202  or host processor  228  or both, can cause the device including system  200  to perform one or more functions and methods of one or more examples of this disclosure. 
     Touch screen  220  can include touch sensing circuitry that can include a capacitive sensing medium having a plurality of drive lines  222  and a plurality of sense lines  223 . It should be noted that the term “lines” is sometimes used herein to mean simply conductive pathways, as one skilled in the art will readily understand, and is not limited to elements that are strictly linear, but includes pathways that change direction, and includes pathways of different size, shape, materials, etc. Drive lines  222  can be driven by stimulation signals  216  from driver logic  214  through a drive interface  224 , and resulting sense signals  217  generated in sense lines  223  can be transmitted through a sense interface  225  to sense channels  208  (also referred to as an event detection and demodulation circuit) in touch controller  206 . In this way, drive lines and sense lines can be part of the touch sensing circuitry that can interact to form capacitive sensing nodes, which can be thought of as touch picture elements (touch pixels), such as touch pixels  226  and  227 . This way of understanding can be particularly useful when touch screen  220  is viewed as capturing an “image” of touch. In other words, after touch controller  206  has determined whether a touch has been detected at each touch pixel in the touch screen, the pattern of touch pixels in the touch screen at which a touch occurred can be thought of as an “image” of touch (i.e., a pattern of fingers touching the touch screen). 
     In some examples, touch screen  220  can be an integrated touch screen in which touch sensing circuit elements of the touch sensing system can be integrated into the display pixel stackups of a display. An example integrated touch screen in which examples of the disclosure can be implemented will now be described with reference to  FIGS. 3-6 .  FIG. 3  is a more detailed view of touch screen  220  showing an example configuration of drive lines  222  and sense lines  223  according to examples of the disclosure. As shown in  FIG. 3 , each drive line  222  can be formed of one or more drive line segments  301  that can be electrically connected by drive line links  303  at connections  305 . Drive line links  303  are not electrically connected to sense lines  223 , rather, the drive line links can bypass the sense lines through bypasses  307 . Drive lines  222  and sense lines  223  can interact capacitively to form touch pixels such as touch pixels  226  and  227 . Drive lines  222  (i.e., drive line segments  301  and corresponding drive line links  303 ) and sense lines  223  can be formed of electrical circuit elements in touch screen  220 . In the example configuration of  FIG. 3 , each of touch pixels  226  and  227  can include a portion of one drive line segment  301 , a portion of a sense line  223 , and a portion of another drive line segment  301 . For example, touch pixel  226  can include a right-half portion  309  of a drive line segment on one side of a portion  311  of a sense line, and a left-half portion  313  of a drive line segment on the opposite side of portion  311  of the sense line. 
     In some examples, the configuration of drive lines  222  and sense lines  223  can be the reverse of that shown in  FIG. 3 . That is to say that each drive line  222  can be formed of a single drive line segment, whereas each sense line  223  can be formed of one or more sense line segments that can be electrically connected by sense line links. Further, in some examples, guard lines can exist between drive line segments  301  and sense lines  223 . Such guard lines can shield display pixel elements in sense lines from direct coupling to display pixel elements in adjacent drive line segments. For ease of description, the examples of the disclosure will be described with reference to the drive and sense line configuration of  FIG. 3 , although it is understood that the scope of the disclosure is not so limited. 
     The circuit elements in display pixel stackups can include, for example, elements that can exist in conventional LCD displays, as described above. It is noted that circuit elements are not limited to whole circuit components, such a whole capacitor, a whole transistor, etc., but can include portions of circuitry, such as only one of the two plates of a parallel plate capacitor.  FIG. 4  illustrates an example configuration in which common electrodes (Vcom) can form portions of the touch sensing circuitry of a touch sensing system. Each display pixel can include a common electrode  401 , which can be a circuit element of the display system circuitry in the pixel stackup (i.e., the stacked material layers forming the display pixels) of the display pixels of some types of conventional LCD displays, e.g., fringe field switching (FFS) displays, that can operate as part of the display system to display an image. 
     In the example shown in  FIG. 4 , each common electrode (Vcom)  401  can serve as a multi-function circuit element that can operate as display circuitry of the display system of touch screen  220  and can also operate as touch sensing circuitry of the touch sensing system. In this example, each common electrode  401  can operate as a common electrode of the display circuitry of the touch screen, and can also operate together when grouped with other common electrodes as touch sensing circuitry of the touch screen. For example, a group of common electrodes  401  can operate together as a capacitive part of a drive line or a sense line of the touch sensing circuitry during the touch sensing phase. Other circuit elements of touch screen  220  can form part of the touch sensing circuitry by, for example, electrically connecting together common electrodes  401  of a region, switching electrical connections, etc. In general, each of the touch sensing circuit elements may be either a multi-function circuit element that can form part of the touch sensing circuitry and can perform one or more other functions, such as forming part of the display circuitry, or may be a single-function circuit element that can operate as touch sensing circuitry only. Similarly, each of the display circuit elements may be either a multi-function circuit element that can operate as display circuitry and perform one or more other functions, such as operating as touch sensing circuitry, or may be a single-function circuit element that can operate as display circuitry only. Therefore, in some examples, some of the circuit elements in the display pixel stackups can be multi-function circuit elements and other circuit elements may be single-function circuit elements. In other examples, all of the circuit elements of the display pixel stackups may be single-function circuit elements. 
     In addition, although examples herein may describe the display circuitry as operating during a display phase, and describe the touch sensing circuitry as operating during a touch sensing phase, it should be understood that a display phase and a touch sensing phase may be operated at the same time, e.g., partially or completely overlap, or the display phase and touch phase may operate at different times. Also, although examples herein describe certain circuit elements as being multi-function and other circuit elements as being single-function, it should be understood that the circuit elements are not limited to the particular functionality in other examples. In other words, a circuit element that is described in one example herein as a single-function circuit element may be configured as a multi-function circuit element in other examples, and vice versa. 
     For example,  FIG. 4  shows common electrodes  401  grouped together to form drive region segments  403  and sense regions  405  that generally correspond to drive line segments  301  and sense lines  223 , respectively. Grouping multi-function circuit elements of display pixels into a region can mean operating the multi-function circuit elements of the display pixels together to perform a common function of the region. Grouping into functional regions may be accomplished through one or a combination of approaches, for example, the structural configuration of the system (e.g., physical breaks and bypasses, voltage line configurations), the operational configuration of the system (e.g., switching circuit elements on/off, changing voltage levels and/or signals on voltage lines), etc. 
     Multi-function circuit elements of display pixels of the touch screen can operate in both the display phase and the touch phase. For example, during a touch phase, common electrodes  401  can be grouped together to form touch signal lines, such as drive regions and sense regions. In some examples, circuit elements can be grouped to form a continuous touch signal line of one type and a segmented touch signal line of another type. For example,  FIG. 4  shows one example in which drive region segments  403  and sense regions  405  correspond to drive line segments  301  and sense lines  223  of touch screen  220 . Other configurations are possible in other examples; for example, common electrodes  401  could be grouped together such that drive lines are each formed of a continuous drive region and sense lines are each formed of a plurality of sense region segments linked together through connections that bypass a drive region. 
     The drive regions in the example of  FIG. 3  are shown in  FIG. 4  as rectangular regions including a plurality of common electrodes of display pixels, and the sense regions of  FIG. 3  are shown in  FIG. 4  as rectangular regions including a plurality of common electrodes of display pixels extending the vertical length of the LCD. In some examples, a touch pixel of the configuration of  FIG. 4  can include, for example, a 64×64 area of display pixels. However, the drive and sense regions are not limited to the shapes, orientations, and positions shown, but can include any suitable configurations according to examples of the disclosure. It is to be understood that the display pixels used to form the touch pixels are not limited to those described above, but can be any suitable size or shape to permit touch capabilities according to examples of the disclosure. 
       FIG. 5  is a three-dimensional illustration of an exploded view (expanded in the z-direction) of example display pixel stackups  500  showing some of the elements within the pixel stackups of an example integrated touch screen  550 . Stackups  500  can include a configuration of conductive lines that can be used to group common electrodes, such as common electrodes  401 , into drive region segments and sense regions, such as shown in  FIG. 4 , and to link drive region segments to form drive lines. 
     Stackups  500  can include elements in a first metal (M 1 ) layer  501 , a second metal (M 2 ) layer  503 , a common electrode (Vcom) layer  505 , and a third metal (M 3 ) layer  507 . Each display pixel can include a common electrode  509 , such as common electrodes  401  in  FIG. 4 , which is formed in Vcom layer  505 . M 3  layer  507  can include connection element  511  that can electrically connect together common electrodes  509 . In some display pixels, breaks  513  can be included in connection element  511  to separate different groups of common electrodes  509  to form drive region segments  515  and a sense region  517 , such as drive region segments  403  and sense region  405 , respectively. Breaks  513  can include breaks in the x-direction that can separate drive region segments  515  from sense region  517 , and breaks in the y-direction that can separate one drive region segment  515  from another drive region segment. M 1  layer  501  can include tunnel lines  519  that can electrically connect together drive region segments  515  through connections, such as conductive vias  521 , which can electrically connect tunnel line  519  to the grouped common electrodes in drive region segment display pixels. Tunnel line  519  can run through the display pixels in sense region  517  with no connections to the grouped common electrodes in the sense region, e.g., no vias  521  in the sense region. The M 1  layer can also include gate lines  520 . M 2  layer  503  can include data lines  523 . Only one gate line  520  and one data line  523  are shown for the sake of clarity; however, a touch screen can include a gate line running through each horizontal row of display pixels and multiple data lines running through each vertical row of display pixels, for example, one data line for each red, green, blue (RGB) color sub-pixel in each pixel in a vertical row of an RGB display integrated touch screen. 
     Structures such as connection elements  511 , tunnel lines  519 , and conductive vias  521  can operate as a touch sensing circuitry of a touch sensing system to detect touch during a touch sensing phase of the touch screen. Structures such as data lines  523 , along with other pixel stackup elements such as transistors, pixel electrodes, common voltage lines, data lines, etc. (not shown), can operate as display circuitry of a display system to display an image on the touch screen during a display phase. Structures such as common electrodes  509  can operate as multifunction circuit elements that can operate as part of both the touch sensing system and the display system. 
     For example, in operation during a touch sensing phase, gate lines  520  can be held to a fixed voltage while stimulation signals can be transmitted through a row of drive region segments  515  connected by tunnel lines  519  and conductive vias  521  to form electric fields between the stimulated drive region segments and sense region  517  to create touch pixels, such as touch pixel  226  in  FIG. 2 . In this way, the row of connected together drive region segments  515  can operate as a drive line, such as drive line  222 , and sense region  517  can operate as a sense line, such as sense line  223 . When an object such as a finger approaches or touches a touch pixel, the object can affect the electric fields extending between the drive region segments  515  and the sense region  517 , thereby reducing the amount of charge capacitively coupled to the sense region. This reduction in charge can be sensed by a sense channel of a touch sensing controller connected to the touch screen, such as touch controller  206  shown in  FIG. 2 , and stored in a memory along with similar information of other touch pixels to create an “image” of touch. 
     A touch sensing operation according to examples of the disclosure will be described with reference to  FIG. 6 .  FIG. 6  shows partial circuit diagrams of some of the touch sensing circuitry within display pixels in a drive region segment  601  and a sense region  603  of an example touch screen according to examples of the disclosure. For the sake of clarity, only one drive region segment is shown. Also for the sake of clarity,  FIG. 6  includes circuit elements illustrated with dashed lines to signify some circuit elements operate primarily as part of the display circuitry and not the touch sensing circuitry. In addition, a touch sensing operation is described primarily in terms of a single display pixel  601   a  of drive region segment  601  and a single display pixel  603   a  of sense region  603 . However, it is understood that other display pixels in drive region segment  601  can include the same touch sensing circuitry as described below for display pixel  601   a,  and the other display pixels in sense region  603  can include the same touch sensing circuitry as described below for display pixel  603   a.  Thus, the description of the operation of display pixel  601   a  and display pixel  603   a  can be considered as a description of the operation of drive region segment  601  and sense region  603 , respectively. 
     Referring to  FIG. 6 , drive region segment  601  includes a plurality of display pixels including display pixel  601   a.  Display pixel  601   a  can include a TFT  607 , a gate line  611 , a data line  613 , a pixel electrode  615 , and a common electrode  617 .  FIG. 6  shows common electrode  617  connected to the common electrodes in other display pixels in drive region segment  601  through a connection element  619  within the display pixels of drive region segment  601  that is used for touch sensing as described in more detail below. Sense region  603  includes a plurality of display pixels including display pixel  603   a.  Display pixel  603   a  includes a TFT  609 , a data line  614 , a pixel electrode  616 , and a common electrode  618 . TFT  609  can be connected to the same gate line  611  as TFT  607 .  FIG. 6  shows common electrode  618  connected to the common electrodes in other display pixels in sense region  603  through a connection element  620  that can be connected, for example, in a border region of the touch screen to form an element within the display pixels of sense region  603  that is used for touch sensing as described in more detail below. 
     Although display pixels  601   a  and  603   a  have been described as including a single TFT, in some examples the display pixels may include more than a single TFT. For example, display pixel  603   a  can include two TFTs connected in series, the gate terminals of which both being connected to gate line  611 . The same can be true of display pixel  601   a  and other display pixels in the touch screen. The operation of such display pixels can be substantially the same as the operation of the display pixels of  FIG. 6 . For ease of description, the examples of the disclosure will be described with reference to the display pixel configuration of  FIG. 6 , although the scope of the disclosure is not so limited. 
     During a touch sensing phase, gate line  611  can be connected to a power supply, such as a charge pump, that can apply a voltage to maintain TFTs  609  in the “off” state. Drive signals can be applied to common electrodes  617  through a tunnel line  621  that is electrically connected to a portion of connection element  619  within a display pixel  601   b  of drive region segment  601 . The drive signals, which are transmitted to all common electrodes  617  of the display pixels in drive region segment  601  through connection element  619 , can generate an electrical field  623  between the common electrodes of the drive region segment and common electrodes  618  of sense region  603 , which can be connected to a sense amplifier, such as a charge amplifier  626 . Electrical charge can be injected into the structure of connected common electrodes of sense region  603 , and charge amplifier  626  converts the injected charge into a voltage that can be measured. The amount of charge injected, and consequently the measured voltage, can depend on the proximity of a touch object, such as a finger  627 , to the drive and sense regions. In this way, the measured voltage can provide an indication of touch on or near the touch screen. 
     Referring again to  FIG. 5 , it can be seen from  FIG. 5  that some display pixels of touch screen  550  include different elements than other display pixels. For example, a display pixel  551  can include a portion of connection element  511  that has breaks  513  in the x-direction and the y-direction, and display pixel  551  does not include tunnel line  519 . A display pixel  553  can include a portion of connection element  511  that has a break  513  in the x-direction, but not in the y-direction, and can include a portion of tunnel line  519  and a via  521 . Other display pixels can include other differences in the configuration of stackup elements including, for example, no breaks  513  in connection element  511 , a portion of tunnel line  519  without a via  521 , etc. 
     The above-described operations for sensing touch can consume power. For example, referring to  FIG. 2 , driving each of drive lines  222  with stimulation signals  216 , sensing sense lines  223 , and processing the resulting sense signals  217  in touch controller  206 , can consume power. In order to reduce power consumed by touch sensing, in some examples, touch screens, such as touch screen  220 , can operate in different modes during which touch sensing can be performed more or less frequently depending on touch activity sensed on the touch screen. 
       FIG. 7  illustrates exemplary operation of touch screen  220  in two modes for reducing power consumption. As illustrated, touch screen  220  can operate in one of two modes: active mode  701  and idle mode  703 . Details about transitioning between active mode  701  and idle mode  703  will be provided later. In both active  701  and idle modes  703 , touch screen  220  can alternate between touch sensing phase  702  and display phase  704 , as described above. However, in active mode  701 , touch screen  220  can transition from display phase  704  to touch sensing phase  702  more frequently than in idle mode  703 . In some examples, the duration of touch sensing phase  702  can be the same in both active  701  and idle modes  703 , though it is understood that this need not be the case. In some examples, in order to allow touch screen  220  to transition to touch sensing phase  702  more frequently in active mode  701 , the duration of display phase  704  in the active mode can be shorter than the duration of the display phase in idle mode  703 , as illustrated. 
     In some examples, touch sensing accuracy can be higher in active mode  701  than in idle mode  703 , because touch sensing accuracy can increase as more samples of touch are collected and analyzed. In particular, as more images of touch are collected and analyzed, the positions (e.g., the centroids) of one or more contacts included in the touch data can be more accurately determined. However, for the reasons described above, this increased touch accuracy can come at the expense of increased power consumption because of the increased frequency with which touch screen  220  can transition to touch sensing phase  702  in active mode  701 . 
     In contrast to active mode  701 , in some examples, touch accuracy can be lower in idle mode  703 , as touch screen  220  can transition to touch sensing phase  702  less frequently than in the active mode. Touch screen  220  can also consume less power in idle mode  703  than in active mode  701  for the reasons given above. 
     Given the above considerations, it can be useful for touch screen  220  to operate in idle mode  703  when higher touch accuracy is not needed or desired so as to conserve power, and to operate in active mode  701  when higher tough accuracy is needed or desired. Therefore, in some examples, touch screen  220  can transition between active mode  701  and idle mode  703  depending on whether touch activity is detected on the touch screen. Specifically, when touch activity is detected on touch screen  220 , the touch screen can operate in active mode  701 , and when touch activity is not detected on the touch screen, the touch screen can operate in idle mode  703 . For example, touch screen  220  can operate in idle mode  703  until a touch input (i.e., any input detected by the touch screen, for example, a contact, a gesture, a tap, a slide, a hover, etc.) is detected on the touch screen. Once a touch input has been detected on touch screen  220 , the touch screen can transition to active mode  701  so as to provide more accurate touch sensing performance for subsequent touch activity that may occur on the touch screen. Subsequently, if touch screen  220  does not detect a touch input for a specified amount of time (e.g., three seconds), the touch screen can return to idle mode  703  operation. In this way, touch screen  220  can save power while no touch activity is detected on the touch screen, but can still provide more accurate touch sensing when touch activity is detected. 
     However, in some examples, accurate touch sensing may not be needed or desired even when touch activity is detected on touch screen  220 . In such cases, transitioning to active mode  701  in response to the detected touch activity can increase power consumption in return for providing touch accuracy that can be in excess of what is needed or desired. In some examples, instead of transitioning to active mode  701  in the above circumstance, touch screen  220  can remain in idle mode  703  to conserve power, while still detecting touch activity at a level of accuracy that can be sufficient for proper touch screen operation. In some examples, a portion of touch screen can transition to active mode  701 , while a remaining portion of touch screen can remain in idle mode  703 . Details about the above examples will be described below. 
       FIG. 8A  illustrates an exemplary circumstance in which the higher touch accuracy of active mode  701  may not be needed or desired for proper touch screen operation. Device  800  can include touch screen  802 . Touch screen  802  can display a user interface (UI) that can include one or more selectable elements  804 . Elements  804  can be sufficiently large and sufficiently spaced apart such that the relatively low touch accuracy of idle mode  703  can allow device  800  to determine which of the one or more elements one or more touch inputs on touch screen  802  may be meant to select. In other words, the UI presented on touch screen  802  can be such that a touch input detected with relatively low accuracy in idle mode  703  can result in an appropriate action taking place on device  800  (e.g., selecting one of elements  804 ). As such, a positive user experience can be maintained even while conserving power by operating in idle mode  703 . Relatively large and/or separated elements are provided as only one example of when higher accuracy touch detection associated with active mode  701  may not be needed or desired to correctly respond to touch activity. It is understood that other examples can exist, and are similarly within the scope of this disclosure. 
     In some examples, one or more applications that may be running on device  800  can provide information as to whether touch screen  802  should operate in active  701  or idle mode  703  such that sufficient touch accuracy is provided for the respective application. In particular, those who create such applications can be in a good position to determine what kind of touch accuracy can be needed or desired for the applications at issue, and this touch accuracy information can be included in the application itself. For example, an application that presents a UI such as that in  FIG. 8A  can inform device  800  that idle mode  703  can be sufficient for proper application performance; in response, the device can allow touch screen  802  to remain in the idle mode when the application is running, even though touch activity may be detected on the touch screen. In some examples, an application can provide that certain UIs that it presents can be navigated in idle mode  703 , while other UIs that it presents should be navigated in active mode  701 . In such examples, device  800  can allow touch screen  802  to transition appropriately between idle and active modes depending on which UI may be currently presented on the device. 
     In some examples, instead of, or in addition to, an application providing information as to whether touch screen  802  should operate in active  701  or idle mode  703 , device  800  can analyze one or more UIs presented by an application that is running on the device to determine whether and/or when to operate the touch screen in the active and the idle modes. For example, if device  800  analyzes a UI being presented on touch screen  802  and determines that higher touch accuracy is needed or desired, the device can allow the touch screen to operate in active mode  701 . On the other hand, if device  800  determines that higher touch accuracy is not needed or desired, the device can maintain touch screen  802  in idle mode  703 . In some examples, device  800  can make the above determination each time a UI is presented on touch screen  802 . 
     In some examples, the touch accuracy of active mode  701  may be needed or desired in some, but not all, portions of a UI presented by an application running on device  800 . Meanwhile, the remaining portions of the UI may be such that the touch accuracy of idle mode  703  can be sufficient. In such circumstances, device  800  can operate one or more portions of touch screen  802  in active mode  701  and one or more other portions of the touch screen in idle mode  703 . 
       FIG. 8B  illustrates an exemplary circumstance in which the touch accuracy of active mode  701  may be needed or desired for some portion(s) of touch screen  802  while the touch accuracy of idle mode  703  may be sufficient for other portion(s) of the touch screen. As above, device  800  can include touch screen  802 . Touch screen  802  can display a UI that includes portion  806  and portion  808 . Portion  806  of the UI can provide visual feedback  810  of a user&#39;s inputting of a passcode as the user inputs it, for example. Portion  808  of the displayed UI can provide a keypad  812  including one or more keys  814 . Keys  814  can be positioned adjacent each other in the UI. The user can enter the passcode, for example, by providing touch input to one or more keys  814  in keypad  812 . It is understood that the UI described above is given by way of example only, and that other types of UIs can similarly have one or more portions in which higher touch accuracy can be needed or desired, and one or more portions in which lower touch accuracy can be sufficient. All such UIs are within the scope of this disclosure. 
     In the example of  FIG. 8B , because portion  806  can simply display information, the touch accuracy of active mode  701  may not be needed or desired in that portion of touch screen  802 . It is noted that other UIs may similarly not need or benefit from increased touch accuracy; for example, the UI of  FIG. 8A . It is understood that other such UIs are similarly within the scope of this disclosure. 
     In contrast to portion  806 , portion  808  of touch screen  802  may require or benefit from the increased touch accuracy of active mode  701  because of the existence of keypad  812  and the need to accurately determine which key(s)  814  of the keypad a user may select when entering a passcode. The benefit from increased touch accuracy can be a result of input elements (e.g., the keys  814  of the keypad  812 ) being positioned relatively close together, for example, such that lower touch accuracy may result in not being able to accurately identify which of two adjacent input elements a touch input may be meant to select; increased touch accuracy, on the other hand, may allow for the desired identification. It is noted that other UIs may similarly need or benefit from increased touch accuracy. It is understood that other such UIs are similarly within the scope of this disclosure. 
     In view of the above, portion  808  of touch screen  802  can operate in active mode  701  while portion  806  of the touch screen can operate in idle mode  703 . Operating more than two portions of a touch screen different modes is understood to be within the scope of this disclosure. In some examples, as the UI displayed on touch screen  802  changes, the portions, the number of portions, and/or their respective operating modes (i.e., active or idle) can be updated accordingly. 
     As described above, in some examples, the determination as to which portion(s) of touch screen  802  are to be operated in which mode (i.e., active or idle) can be informed by information in or provided by an application presenting the UI of interest on the touch screen. Additionally or alternatively, the above determination can be informed by an analysis of the UI performed by device  800 , as described above. 
     Although the description above has been provided with respect to the provided two modes of operation—active and idle—it is understood that more than two modes of operation can be implemented. For example, in some examples, a first mode of operation can provide the highest touch accuracy while consuming the most power, a second mode of operation can provide moderate touch accuracy while consuming moderate power, and a third mode of operation can provide the lowest touch accuracy while consuming the least power. In some examples, a touch screen and/or portions of the touch screen can be operated in one of the above three modes depending on the level of touch accuracy needed or desired. Modes in excess of three are similarly within the scope of this disclosure. 
     Further, although the above modes of operation have been described as performing touch sensing at different rates (i.e., frequency of touch sensing) to appropriately adjust power consumption, in some examples, power consumption can be changed by changing the number of drive and/or sense lines on a touch screen that are being driven and/or sensed. For example, for lower touch accuracy and lower power consumption, every other drive and/or sense line can be driven and/or sensed. Such a mode of operation can provide lower touch accuracy not because touch is being sensed less frequently (as in the examples above), but rather because touch can be sensed at fewer locations (i.e., sensors) on the touch screen. In some examples, lower touch sensing frequency and driving/sensing fewer drive/sense lines can be utilized in combination to obtain desired touch accuracy and power consumption levels. The above modes of operation can be applied to the entire touch screen and/or one or more portions of the touch screen, as previously described. 
       FIG. 9  illustrates an exemplary process  900  by which operation of touch screen  220  can be determined. At step  902 , it can be determined whether the entire touch screen should operate in a single mode of operation (e.g., active or idle), or whether portions of the touch screen should operate in different or independent modes of operation. As discussed above, this determination can be based on information provided by an application that may be running on a device of this disclosure, analysis of a UI by the device itself, or any combination of the above. 
     If the entire touch screen is to operate in a single mode, at step  904 , it can be determined whether that mode should provide higher touch accuracy or lower touch accuracy. As stated above, this determination can be based on information provided by an application that may be running on a device of this disclosure, analysis of a UI by the device itself, or any combination of the above. If higher touch accuracy is not needed or desired, the touch screen can operate in idle mode  908 . If higher touch accuracy is needed or desired, the touch screen can operate in active mode  906 . It is understood, as discussed above, that two modes of operation are given by way of example only, and that operating in more than two modes is also within the scope of this disclosure. 
     Referring back to step  902 , if portions of the touch screen are to operate in individual modes, the one or more portions requiring higher touch accuracy and the one or more portions requiring lower touch accuracy can be determined at step  910 . As stated above, this determination can be based on information provided by an application that may be running on a device of this disclosure, analysis of a UI by the device itself, or any combination of the above. Further, if more than two modes of operation exist, the determination as to which portion(s) should be operated in which of the modes of operation can be performed at step  910 . 
     At step  912 , the portions identified in step  910  can be operated in their respective modes. 
     Process  900  can be run at many different moments or times. In some examples, the determinations of process  900  can be made at regular or irregular intervals of time. In some examples, the determinations of process  900  can be made each time an application runs on the device of this disclosure. In some examples, the determinations of process  900  can be made each time a UI is displayed on the touch screen of this disclosure. Further, in some examples, some, but not all, of the steps of process  900  can be performed at each of the above moments or times. It is understood that process  900  is given as only one example of how operation of the touch screen of this disclosure can be determined. Other ways to determine touch screen operation can exist and are similarly within the scope of this disclosure. 
     Therefore, according to the above, some examples of the disclosure are directed to a method comprising determining a first level of touch accuracy, and based on at least the determination of the first level of touch accuracy, operating a first portion of a touch screen in a first mode, the first mode corresponding to the first level of touch accuracy. Additionally or alternatively to one or more of the examples disclosed above, in some examples, operating the first portion of the touch screen in the first mode comprises transitioning the first portion of the touch screen between a touch sensing phase and a display phase at a first transition frequency. Additionally or alternatively to one or more of the examples disclosed above, in some examples, operating the first portion of the touch screen in the first mode comprises sensing touch at a first set of touch sensors, the first portion of the touch screen comprising the first set of touch sensors and a second set of touch sensors. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the method further comprises determining a second level of touch accuracy, the second level of touch accuracy being different than the first level of touch accuracy, and based on at least the determination of the second level of touch accuracy, operating a second portion of the touch screen in a second mode, the second mode corresponding to the second level of touch accuracy. Additionally or alternatively to one or more of the examples disclosed above, in some examples, operating the first portion of the touch screen in the first mode comprises transitioning the first portion of the touch screen between a touch sensing phase and a display phase at a first transition frequency, and operating the second portion of the touch screen in the second mode comprises transitioning the second portion of the touch screen between a touch sensing phase and a display phase at a second transition frequency, different from the first transition frequency. Additionally or alternatively to one or more of the examples disclosed above, in some examples, operating the first portion of the touch screen in the first mode comprises sensing touch at a first set of touch sensors, the first portion of the touch screen comprising the first set of touch sensors and a second set of touch sensors, operating the second portion of the touch screen in the second mode comprises sensing touch at a third set of touch sensors, the second portion of the touch screen comprising the third set of touch sensors and a fourth set of touch sensors, and a first ratio of a first number of touch sensors in the first set to a second number of touch sensors in the second set is different than a second ratio of a third number of touch sensors in the third set to a fourth number of touch sensors in the fourth set. Additionally or alternatively to one or more of the examples disclosed above, in some examples, determining the first level of touch accuracy comprises determining the first level of touch accuracy based on at least an application running on a device including the touch screen. Additionally or alternatively to one or more of the examples disclosed above, in some examples, determining the first level of touch accuracy comprises determining the first level of touch accuracy based on at least a user interface (UI) for display on the touch screen. 
     Some examples of the disclosure are directed to a non-transitory computer-readable storage medium having stored therein instructions, which when executed by a device, cause the device to perform a method comprising determining a first level of touch accuracy, and based on at least the determination of the first level of touch accuracy, operating a first portion of a touch screen in a first mode, the first mode corresponding to the first level of touch accuracy. Additionally or alternatively to one or more of the examples disclosed above, in some examples, operating the first portion of the touch screen in the first mode comprises transitioning the first portion of the touch screen between a touch sensing phase and a display phase at a first transition frequency. Additionally or alternatively to one or more of the examples disclosed above, in some examples, operating the first portion of the touch screen in the first mode comprises sensing touch at a first set of touch sensors, the first portion of the touch screen comprising the first set of touch sensors and a second set of touch sensors. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the method further comprises determining a second level of touch accuracy, the second level of touch accuracy being different than the first level of touch accuracy, and based on at least the determination of the second level of touch accuracy, operating a second portion of the touch screen in a second mode, the second mode corresponding to the second level of touch accuracy. Additionally or alternatively to one or more of the examples disclosed above, in some examples, operating the first portion of the touch screen in the first mode comprises transitioning the first portion of the touch screen between a touch sensing phase and a display phase at a first transition frequency, and operating the second portion of the touch screen in the second mode comprises transitioning the second portion of the touch screen between a touch sensing phase and a display phase at a second transition frequency, different from the first transition frequency. Additionally or alternatively to one or more of the examples disclosed above, in some examples, operating the first portion of the touch screen in the first mode comprises sensing touch at a first set of touch sensors, the first portion of the touch screen comprising the first set of touch sensors and a second set of touch sensors, operating the second portion of the touch screen in the second mode comprises sensing touch at a third set of touch sensors, the second portion of the touch screen comprising the third set of touch sensors and a fourth set of touch sensors, and a first ratio of a first number of touch sensors in the first set to a second number of touch sensors in the second set is different than a second ratio of a third number of touch sensors in the third set to a fourth number of touch sensors in the fourth set. Additionally or alternatively to one or more of the examples disclosed above, in some examples, determining the first level of touch accuracy comprises determining the first level of touch accuracy based on at least an application running on a device including the touch screen. Additionally or alternatively to one or more of the examples disclosed above, in some examples, determining the first level of touch accuracy comprises determining the first level of touch accuracy based on at least a user interface (UI) for display on the touch screen. 
     Some examples of the disclosure are directed to an electronic device, comprising a processor to execute instructions, a touch screen, and a memory coupled with the processor to store instructions, which when executed by the processor, cause the processor to perform a method comprising determining a first level of touch accuracy, and based on at least the determination of the first level of touch accuracy, operating a first portion of the touch screen in a first mode, the first mode corresponding to the first level of touch accuracy. Additionally or alternatively to one or more of the examples disclosed above, in some examples, operating the first portion of the touch screen in the first mode comprises transitioning the first portion of the touch screen between a touch sensing phase and a display phase at a first transition frequency. Additionally or alternatively to one or more of the examples disclosed above, in some examples, operating the first portion of the touch screen in the first mode comprises sensing touch at a first set of touch sensors, the first portion of the touch screen comprising the first set of touch sensors and a second set of touch sensors. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the method further comprises determining a second level of touch accuracy, the second level of touch accuracy being different than the first level of touch accuracy, and based on at least the determination of the second level of touch accuracy, operating a second portion of the touch screen in a second mode, the second mode corresponding to the second level of touch accuracy. Additionally or alternatively to one or more of the examples disclosed above, in some examples, operating the first portion of the touch screen in the first mode comprises transitioning the first portion of the touch screen between a touch sensing phase and a display phase at a first transition frequency, and operating the second portion of the touch screen in the second mode comprises transitioning the second portion of the touch screen between a touch sensing phase and a display phase at a second transition frequency, different from the first transition frequency. Additionally or alternatively to one or more of the examples disclosed above, in some examples, operating the first portion of the touch screen in the first mode comprises sensing touch at a first set of touch sensors, the first portion of the touch screen comprising the first set of touch sensors and a second set of touch sensors, operating the second portion of the touch screen in the second mode comprises sensing touch at a third set of touch sensors, the second portion of the touch screen comprising the third set of touch sensors and a fourth set of touch sensors, and a first ratio of a first number of touch sensors in the first set to a second number of touch sensors in the second set is different than a second ratio of a third number of touch sensors in the third set to a fourth number of touch sensors in the fourth set. Additionally or alternatively to one or more of the examples disclosed above, in some examples, determining the first level of touch accuracy comprises determining the first level of touch accuracy based on at least an application running on a device including the touch screen. Additionally or alternatively to one or more of the examples disclosed above, in some examples, determining the first level of touch accuracy comprises determining the first level of touch accuracy based on at least a user interface (UI) for display on the touch screen. 
     Although examples of this disclosure have been fully described with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art. Such changes and modifications are to be understood as being included within the scope of examples of this disclosure as defined by the appended claims.