PATENT DOCUMENT

Publication Number: US-10042459-B2
Application Number: US-201514847404-A
Country: US
Kind Code: B2

Title: Dynamic voltage generation for touch-enabled displays

Abstract:
The disclosed embodiments relate to a system that provides power for a touch-enabled display, wherein the touch-enabled display cycles between a display mode and a touch mode. During the display mode, the system drives a display-mode voltage to the touch-enabled display through a power output, wherein the power output is coupled through a display-mode capacitor C D  to ground. Next, during a transition from the display mode to the touch mode, the system couples the power output through a touch-mode capacitor C T  to ground, wherein C T  was previously charged to a touch-mode voltage, which causes the power output to rapidly transition to the touch-mode voltage. Then, during the touch mode, the system drives the touch-mode voltage through the power output.

Claims:
What is claimed is: 
     
       1. A method for providing power for a touch-enabled display, comprising:
 during a display mode, driving a display-mode voltage through a power output, wherein the power output is coupled to:
 a display-mode capacitor C D , and 
 a touch-mode capacitor C T ; and 
 
 during a transition from the display mode to a touch mode, causing a change in:
 a voltage at a first terminal of the touch-mode capacitor C T , 
 a voltage at a second terminal of the touch-mode capacitor C T , 
 a voltage at at least one terminal of the display-mode capacitor C D , and 
 a voltage at the power output. 
 
 
     
     
       2. The method of  claim 1 , wherein:
 during the display mode, the power output is uncoupled, through the touch-mode capacitor C T , from ground, and 
 during the touch mode, the power output is coupled, through the touch-mode capacitor C T , to the ground. 
 
     
     
       3. The method of  claim 1 , further comprising:
 during the touch mode, driving a touch-mode voltage through the power output. 
 
     
     
       4. The method of  claim 1 , further comprising:
 during the touch mode, coupling the touch-mode capacitor C T  in parallel with the display-mode capacitor C D  between the power output and ground; 
 wherein a capacitance of the touch-mode capacitor C T  is larger than a capacitance of the display-mode capacitor C D , and the touch-mode capacitor C T  dominates the display-mode capacitor C D  during the touch mode. 
 
     
     
       5. The method of  claim 1 , further comprising, during the transition from the display mode to the touch mode, uncoupling the display-mode capacitor C D  from ground. 
     
     
       6. The method of  claim 1 ,
 wherein the power output is a low output, the low output providing a low display-mode voltage during the display mode and providing a low touch-mode voltage during the touch mode; and 
 wherein a second power output is associated with a high output, the high output providing a high display-mode voltage during the display mode and providing a high touch-mode voltage during the touch mode. 
 
     
     
       7. The method of  claim 1 , wherein during the display mode, the display-mode capacitor C D  is charged to a first voltage, the display-mode voltage being based on the first voltage, and the touch-mode capacitor C T  is charged to a second voltage, different than the first voltage. 
     
     
       8. The method of  claim 7 , wherein during the transition from the display mode to the touch mode, the display-mode capacitor C D  remains charged to the first voltage and the touch-mode capacitor C T  remains charged to the second voltage. 
     
     
       9. The method of  claim 1 , wherein:
 during the display mode, the display-mode capacitor C D  is electrically coupled between the power output and a first node, and the touch-mode capacitor C T  is electrically coupled between the power output and a second node, different than the first node, and 
 during the touch mode, the display-mode capacitor C D  is electrically coupled between the power output and the first node, and the touch-mode capacitor C T  is electrically coupled between the power output and the first node and the second node. 
 
     
     
       10. The method of  claim 9 , wherein the first node is ground, and the second node is a power source. 
     
     
       11. The method of  claim 1 , wherein:
 during the display mode, one terminal of the touch-mode capacitor C T , opposite a terminal of the touch-mode capacitor C T  coupled to the power output, is coupled to a first voltage, and 
 the voltage changes at the first and second terminals of the touch-mode capacitor C T , the at least one terminal of the display-mode capacitor C D , and the power output result from coupling the one terminal of the touch-mode capacitor C T  to a second voltage, different than the first voltage. 
 
     
     
       12. An apparatus that provides power for a touch-enabled display, comprising:
 a display-mode capacitor C D  coupled to a power output; 
 a touch-mode capacitor C T  coupled to the power output; and 
 a controller for the touch-enabled display configured to:
 cycle between a display mode and a touch mode; 
 provide power to the touch-enabled display through the power output; and 
 during a transition from the display mode to the touch mode, causing a change in:
 a voltage at a first terminal of the touch-mode capacitor C T , 
 a voltage at a second terminal of the touch-mode capacitor C T , 
 a voltage at at least one terminal of the display-mode capacitor C D , and 
 a voltage at the power output. 
 
 
 
     
     
       13. The apparatus of  claim 12 , wherein the controller is configured to:
 during the display mode, uncouple the power output, through the touch-mode capacitor C T , from ground, and 
 during the touch mode, couple the power output, through the touch-mode capacitor C T , to the ground. 
 
     
     
       14. The apparatus of  claim 12 , wherein the controller is configured to, during the touch mode, drive a touch-mode voltage through the power output. 
     
     
       15. The apparatus of  claim 12 , wherein the controller is configured to, during the touch mode, couple the touch-mode capacitor C T  in parallel with the display-mode capacitor C D  between the power output and ground;
 wherein a capacitance of the touch-mode capacitor C T  is larger than a capacitance of the display-mode capacitor C D , and the touch-mode capacitor C T  dominates the display-mode capacitor C D  during the touch mode. 
 
     
     
       16. The apparatus of  claim 12 ,
 wherein the power output is a low output, the low output providing a low display-mode voltage during the display mode and providing a low touch-mode voltage during the touch mode; and 
 wherein a second power output is associated with a high output, the high output providing a high display-mode voltage during the display mode and providing a high touch-mode voltage during the touch mode. 
 
     
     
       17. The apparatus of  claim 12 , wherein the controller is configured to:
 during the display mode, couple the display-mode capacitor C D  between the power output and a first node and the touch-mode capacitor C T  between the power output and a second node, different than the first node, and 
 during the touch mode, couple display-mode capacitor C D  between the power output and the first node and the touch-mode capacitor C T  between the power output and the first node and the second node. 
 
     
     
       18. The apparatus of  claim 17 , wherein the first node is ground, and the second node is a power source. 
     
     
       19. The apparatus of  claim 12 , wherein the controller is configured to:
 during the display mode:
 charge the display-mode capacitor C D  to a first voltage, the display-mode voltage being based on the first voltage, and 
 charge the touch-mode capacitor C T  is charged to a second voltage, different than the first voltage. 
 
 
     
     
       20. The apparatus of  claim 12 , wherein the controller is configured to, during the display mode, couple one terminal of the touch-mode capacitor C T , opposite a terminal of the touch-mode capacitor C T  coupled to the power output, to a first voltage, and
 wherein the voltage changes at the first and second terminals of the touch-mode capacitor C T , the at least one terminal of the display-mode capacitor C D , and the power output result from coupling the one terminal of the touch-mode capacitor C T  to a second voltage, different than the first voltage. 
 
     
     
       21. The apparatus of  claim 12 , wherein during the transition from the display mode to the touch mode, the display-mode capacitor C D  remains charged to the first voltage and the touch-mode capacitor C T  remains charged to the second voltage. 
     
     
       22. A touch-enabled display, comprising:
 a touch screen comprising a plurality of display pixels; 
 a display system that updates the display pixels during a display mode; 
 a touch sensing system that senses touches on the touch screen during a touch mode; 
 a display-mode capacitor C D  coupled to a power output; 
 a touch-mode capacitor C T  coupled to the power output; and 
 a controller for the touch-enabled display, the controller configured to:
 cycle between the display mode and the touch mode; 
 provide power to the touch-enabled display through the power output; and 
 during a transition from the display mode to the touch mode, cause a change in:
 a voltage at a first terminal of the touch-mode capacitor C T , 
 a voltage at a second terminal of the touch-mode capacitor C T , 
 a voltage at at least one terminal of the display-mode capacitor C D , and 
 a voltage at the power output. 
 
 
 
     
     
       23. The touch-enabled display of  claim 22 , wherein the controller is configured to:
 during the display mode, uncouple the power output, through the touch-mode capacitor C T , from ground, and 
 during the touch mode, couple the power output, through the touch-mode capacitor C T , to the ground. 
 
     
     
       24. The touch-enabled display of  claim 22 , wherein the controller is configured to, during the touch mode, drive a touch-mode voltage through the power output. 
     
     
       25. The touch-enabled display of  claim 22 , wherein the controller is configured to:
 during the touch mode, couple the touch-mode capacitor C T  in parallel with the display-mode capacitor C D  between the power output and ground; 
 wherein a capacitance of the touch-mode capacitor C T  is larger than a capacitance of the display-mode capacitor C D , and the touch-mode capacitor C T  dominates the display-mode capacitor C D  during the touch mode. 
 
     
     
       26. The touch-enabled display of  claim 22 , wherein the power output is a low output, the low output providing a low display-mode voltage during the display mode and providing a low touch-mode voltage during the touch mode; and
 wherein a second power output is associated with a high output, the high output providing a high display-mode voltage during the display mode and providing a high touch-mode voltage during the touch mode. 
 
     
     
       27. The touch-enabled display of  claim 22 , wherein during the display mode, the display-mode capacitor C D  is charged to a first voltage, the display-mode voltage being based on the first voltage, and the touch-mode capacitor C T  is charged to a second voltage, different than the first voltage. 
     
     
       28. The touch-enabled display of  claim 22 , wherein:
 during the display mode, the display-mode capacitor C D  is electrically coupled between the power output and a first node, and the touch-mode capacitor C T  is electrically coupled between the power output and a second node, different than the first node, and 
 during the touch mode, the display-mode capacitor C D  is electrically coupled between the power output and the first node, and the touch-mode capacitor C T  is electrically coupled between the power output and the first node and the second node. 
 
     
     
       29. The touch-enabled display of  claim 22 , wherein:
 during the display mode, one terminal of the touch-mode capacitor C T , opposite a terminal of the touch-mode capacitor C T  coupled to the power output, is coupled to a first voltage, and 
 the voltage changes at the first and second terminals of the touch-mode capacitor C T , the at least one terminal of the display-mode capacitor C D , and the power output result from coupling the one terminal of the touch-mode capacitor C T  to a second voltage, different than the first voltage. 
 
     
     
       30. The touch-enabled display of  claim 22 , wherein the first node is ground, and the second node is a power source. 
     
     
       31. The touch-enabled display of  claim 22 , wherein during the transition from the display mode to the touch mode, the display-mode capacitor C D  remains charged to the first voltage and the touch-mode capacitor C T  remains charged to the second voltage. 
     
     
       32. A non-transitory computer readable storage medium containing instructions that, when executed by a processor of an electronic device, cause the processor to perform a method for providing power for a touch-enabled display, the method comprising:
 during a display mode, drive a display-mode voltage through a power output, wherein the power output is coupled to:
 a display-mode capacitor C D , and 
 a touch-mode capacitor C T ; and 
 
 during a transition from the display mode to a touch mode, cause a change in:
 a voltage at a first terminal of the touch-mode capacitor C T , 
 a voltage at a second terminal of the touch-mode capacitor C T , 
 a voltage at at least one terminal of the display-mode capacitor C D , and a voltage at the power output.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application of U.S. Non-provisional application Ser. No. 13/563,412, filed Jul. 31, 2012, which claims the benefit of U.S. Provisional Application No. 61/657,426, filed Jun. 8, 2012, the entire contents of the chain of applications is incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     The disclosed embodiments generally relate to the design of touch screens for computing devices. More specifically, the disclosed embodiments relate to the design of a power management system that provides power for a touch-enabled display. 
     Many types of input devices are presently used in computing systems, 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 allow a user to perform various functions by touching the touch sensor panel using a finger, stylus or other object at a location 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 can perform one or more actions based on the touch. 
     One challenge in designing touch screens is that the circuitry which displays images generally operates at a different voltage than the significantly more-sensitive circuitry that senses the touches. To deal with this problem, touch-enabled displays typically cycle between a “display mode,” wherein the system operates at a corresponding display-mode voltage, and a “touch mode” wherein the system operates at a touch-mode voltage. However, it is challenging to design a power delivery system that can switch between these voltage levels quickly and efficiently. 
     SUMMARY 
     The disclosed embodiments relate to a system that provides power for a touch-enabled display, wherein the touch-enabled display cycles between a display mode and a touch mode. During the display mode, the system drives a display-mode voltage to the touch-enabled display through a power output, wherein the power output is coupled through a display-mode capacitor CD to ground. Next, during a transition from the display mode to the touch mode, the system couples the power output through a touch-mode capacitor CT to ground, wherein CT was previously charged to a touch-mode voltage and consequently causes the power output to rapidly transition to the touch-mode voltage. Then, during the touch mode, the system drives the touch-mode voltage through the power output. 
     In some embodiments, during a transition between the touch mode and the display mode, the system uncouples C T  from between the power output and ground. 
     In a variation in these embodiments, during the touch mode, the system uses an auxiliary power source to charge the uncoupled touch-mode capacitor CT to the touch-mode voltage. 
     In some embodiments, during the touch mode, CT is coupled in parallel with CD between the power output and ground. In these embodiments, the capacitance on CT is larger than the capacitance on CD, so that CT dominates CD during the touch mode. 
     In some embodiments, during the transition between the display mode and the touch mode, C D  is uncoupled from between the power output and ground. 
     In some embodiments, the power output is a low output which provides a low display-mode voltage during the display mode and a low touch-mode voltage during the touch mode. Moreover, this low output is associated with a high output which provides a high display-mode voltage during the display mode and a high touch-mode voltage during the touch mode. 
     In some embodiments, during the display mode, the system drives a high display-mode voltage to the touch-enabled display through the high output, wherein the high output is coupled through a high-voltage display-mode capacitor C HD  to ground. Next, during the transition from the display mode to the touch mode, the system couples the high output through a high-voltage touch-mode capacitor C HT  to ground, wherein C HT  was previously charged to a high touch-mode voltage, thereby causing the high output to rapidly transition to the high touch-mode voltage. Next, during the touch mode, the system drives the high touch-mode voltage through the high output. 
     In some embodiments, driving the display-mode and touch-mode voltages through the power output involves using a charge pump to drive the display-mode and touch-mode voltages. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A-1C  illustrate an exemplary mobile telephone, an exemplary media player, and an exemplary personal computer that each include an exemplary touch screen according to embodiments of the disclosure. 
         FIG. 2  presents a block diagram of an exemplary computing system that illustrates one implementation of an exemplary touch screen according to embodiments of the disclosure. 
         FIG. 3  provides a more-detailed view of the touch screen of  FIG. 2  showing an exemplary configuration of drive lines and sense lines according to embodiments of the disclosure. 
         FIG. 4  illustrates an exemplary configuration in which touch sensing circuitry includes common electrodes (Vcom) according to embodiments of the disclosure. 
         FIG. 5  illustrates an exploded view of exemplary display pixel stackups according to embodiments of the disclosure. 
         FIG. 6  illustrates an exemplary touch sensing operation according to embodiments of the disclosure. 
         FIG. 7  illustrates an exemplary touch screen device according to various embodiments. 
         FIG. 8  presents a timing diagram for an exemplary power-management technique for a touch sensing system according to various embodiments. 
         FIGS. 9A-9B  illustrate how power is switched through different capacitors according to embodiments of the disclosure. 
         FIG. 10  presents a timing diagram illustrating how power is switched between different capacitors according to embodiments of the disclosure. 
         FIG. 11A  illustrates an alternative embodiment that alternates switching power through a display capacitor and a touch capacitor according to embodiments of the disclosure. 
         FIG. 11B  presents a timing diagram for the embodiment illustrated in  FIG. 11A  according to embodiments of the disclosure. 
         FIG. 12A  illustrates a variation of this alternative embodiment that uses NFET transistors according to embodiments of the disclosure. 
         FIG. 12B  presents a timing diagram for the embodiment illustrated in  FIG. 12A  according to embodiments of the disclosure. 
         FIG. 13A  illustrates a variation of this alternative embodiment that uses NFET and PFET transistors according to embodiments of the disclosure. 
         FIG. 13B  presents a timing diagram for the embodiment illustrated in  FIG. 13A  according to embodiments of the disclosure. 
         FIG. 14A  illustrates a variation of this alternative embodiment that uses NFET transistors without body diode conduction according to embodiments of the disclosure. 
         FIG. 14B  presents a timing diagram for the embodiment illustrated in  FIG. 14A  according to embodiments of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The following description is presented to enable any person skilled in the art to make and use the disclosed embodiments, and is provided in the context of a particular application and its requirements. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the disclosed embodiments. Thus, the disclosed embodiments are not limited to the embodiments shown, but are to be accorded the widest scope consistent with the principles and features disclosed herein. 
     The data structures and code described in this detailed description are typically stored on a non-transitory computer-readable storage medium, which may be any device or medium that can store code and/or data for use by a computer system. The non-transitory computer-readable storage medium includes, but is not limited to, volatile memory, non-volatile memory, magnetic and optical storage devices such as disk drives, magnetic tape, CDs (compact discs), DVDs (digital versatile discs or digital video discs), or other media capable of storing code and/or data now known or later developed. 
     The methods and processes described in the detailed description section can be embodied as code and/or data, which can be stored in a non-transitory computer-readable storage medium as described above. When a computer system reads and executes the code and/or data stored on the non-transitory computer-readable storage medium, the computer system performs the methods and processes embodied as data structures and code and stored within the non-transitory computer-readable storage medium. Furthermore, the methods and processes described below can be included in hardware modules. For example, the hardware modules can include, but are not limited to, application-specific integrated circuit (ASIC) chips, field-programmable gate arrays (FPGAs), and other programmable-logic devices now known or later developed. When the hardware modules are activated, the hardware modules perform the methods and processes included within the hardware modules. 
       FIGS. 1A-1C  show exemplary systems in which a touch screen according to embodiments of the disclosure may be implemented.  FIG. 1A  illustrates an exemplary mobile telephone  136  that includes a touch screen  124 .  FIG. 113  illustrates an exemplary digital media player  140  that includes a touch screen  126 .  FIG. 1C  illustrates an exemplary 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 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 (e.g., orthogonal). Touch pixels can be formed at the intersections 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 embodiments, 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 exemplary computing system  200  that illustrates one implementation of an exemplary touch screen  220  according to embodiments 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 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 embodiments, touch controller  206 , touch processor  202  and peripherals  204  can be integrated into a single application-specific integrated circuit (ASIC). 
     Computing system  200  can also 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 an LCD driver  234 . 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 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 other 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. 
     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 (e.g. a pattern of fingers touching the touch screen). 
     In some exemplary embodiments, 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 exemplary integrated touch screen in which embodiments 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 exemplary configuration of drive lines  222  and sense lines  223  according to embodiments of the disclosure. 
     As shown in  FIG. 3 , each drive line  222  can be formed of one or more drive line portions  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 exemplary 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. The circuit elements 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 exemplary configuration in which common electrodes (Vcom) can form portions of the touch sensing circuitry of a touch sensing system. Each display pixel includes a common electrode  401 , which is 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 multifunction 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 embodiments, 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 embodiments, all of the circuit elements of the display pixel stackups may be single-function circuit elements. 
     In addition, although exemplary embodiments 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 exemplary embodiments 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 embodiments. In other words, a circuit element that is described in one exemplary embodiment herein as a single-function circuit element may be configured as a multi-function circuit element in other embodiments, 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 embodiments 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 embodiment 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 embodiments; 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 embodiments, 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 embodiments 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 embodiments of the disclosure. 
       FIG. 5  is a three-dimensional illustration of an exploded view (expanded in the z-direction) of exemplary display pixel stackups  500  showing some of the elements within the pixel stackups of an exemplary 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 , that is formed in Vcom layer  505 . M 3  layer  507  can include connection element (M 3 )  511  that can electrically connect 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 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 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 embodiments 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 exemplary touch screen according to embodiments 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 that 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 structure  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 structure  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. 
     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 TFT  609  in the “off” state. Drive signals can be applied to common electrode  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 electrode  618  of sense region  603 , which can be connected to a sense amplifier, such as a charge amplifier  626 . The 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 proximity of various circuit elements of integrated touch screens, such as touch screen  550 , can result in coupling of signals between different systems of the touch screen. For example, noise that is generated by power systems, such as a gate line system that applies voltage to gate lines of the touch screen during a touch sensing phase, can be coupled into the touch sensing system, which can potentially corrupt touch sensing signals. 
       FIGS. 7 and 8  illustrate an exemplary touch screen device  700  and an exemplary power management method, respectively, that can reduce or eliminate the effect of power system noise on a touch sensing system according to various embodiments.  FIG. 7  illustrates a touch screen device  700 , which can include a touch screen  701  and a touch screen controller  703 . Touch screen  701  can be an integrated touch screen, such as touch screen  550 , in which the common electrodes can operate as a common voltage source during a display phase and can operate as drive lines and sense lines during a touch sensing phase. For the sake of clarity, only one drive Vcom line  705  and one sense Vcom line  707  are illustrated in the figure. Touch screen  701  can also include gate drivers  709  and gate lines  711 . 
     Touch screen controller  703  can be a combined touch and display controller, and can include both a touch controller  713 , which can control the touch sensing operation of touch screen  701 , and a display controller, such as LCM controller  715 , which can control the display operation of the touch screen. In this regard, some of the components of touch screen controller  703  can be shared between LCM controller  715  and touch controller  713 . For example, a charge pump system, including a charge pump clock selector  717 , a negative charge pump  719 , and a positive charge pump  721 , can be used during both the display and touch phases, as described in more detail below. A synchronization signal (BSYNC)  723  between LCM controller  715  and touch controller  713  can be used to synchronize the display and touch sensing operations. For example, the display phase can correspond to a low BSYNC  723  signal, and the touch phase can correspond to a high BSYNC  723  signal. 
     During the display phase, a first Vcom multiplexer (VCOM MUX I)  725  and a second Vcom multiplexer (VCOM MUX II)  727  can connect the common electrodes (not shown) of touch screen  701  to a Vcom voltage source (not shown) controlled by LCM controller  715 , thus allowing LCM controller  715  to apply a Vcom voltage (VCOM)  729  to the common electrodes. LCM controller  715  can update the image displayed on touch screen  701  by applying data voltages to data lines  731  while scanning gate lines  711 . LCM controller  715  can scan the gate lines using timing signals  733  to control gate drivers  709 , and charge pump clock selector  717  can select the LCM controller to control negative charge pump  719  and positive charge pump  721  to apply a VGL  735  (low gate voltage) and a VGH  737  (high gate voltage) to gate lines  711  through gate drivers  709 . Specifically, charge pump clock selector  717  can select signals LCM_CPL_CLK  739  and LCM_CPH_CLK  741  from LCM controller  715  as negative charge pump clock signal (VGL_CP_CLK)  743  and positive charge pump clock signal (VGH_CP_CLK)  745 , respectively, to control negative charge pump  719  and positive charge pump  721 . For the sake of clarity, a single charge pump system is shown in  FIG. 7 , although it is to be understood that a second charge pump system can be used to apply voltages to additional gate drivers  709  on an opposite side of touch screen  701 , such that some gate lines  711  can be driven from one side of the touch screen and other gate lines  711  can be driven from the other side of the touch screen. In some embodiments, a positive and negative inductive boost regulator can be used instead of the positive and negative charge pump. In either exemplary configuration, subsequent voltage regulators, such as low dropout regulators (LDOs), can be used to stabilize the VGL  735  and/or VGH  737  rails. In this exemplary embodiment, the pixel TFTs (not shown) can be switched off with VGL  735  (e.g., −10 V) and switched on with VGH  737  (e.g., +10 V). However, one skilled in the art would understand that different voltage levels can be used depending on, for example, the particular type of transistor used for the pixel TFT. 
     During the touch sensing phase, the charge pump system can be used by touch controller  713 . Specifically, charge pump clock selector  717  can select signals TOUCH_CPL_CLK  747  and TOUCH_CPH_CLK  749  from touch controller  713  as negative charge pump clock signal (VGL_CP_CLK)  743  and positive charge pump clock signal (VGH_CP_CLK)  745 , respectively, to control negative charge pump  719  and positive charge pump  721 , to apply VGL  735  and VGH  737  to gate lines  711  through gate drivers  709 . In this exemplary embodiment, all of the gate lines can be held at the low gate voltage in order to switch off all of the pixel TFTs during the touch sensing phase. In other words, VGL  735  can be applied to all of the gate lines during the touch sensing phase in the present exemplary embodiment. 
     Touch controller  713  can also send a signal TOUCH_CP_EN  751  to charge pump clock selector  717  to select whether the charge pumps are enabled or disabled, as described in more detail below. 
     VCOM MUX II  727  can connect the common electrodes associated with each sense Vcom line  707  to a corresponding sense channel  753 . Touch controller  713  can scan the drive Vcom lines  705  by controlling VCOM MUX I  725  to connect the common electrodes associated with the drive Vcom lines to drive channels  755  in a particular scanning order while applying drive signals (VSTM)  757  to drive Vcom lines  705 . Each drive signal  757  can be coupled to a sense Vcom line  707  through a signal capacitance (CSIG)  759  that can vary depending on the proximity of a touch object, such as a finger, resulting in a sense signal on the sense Vcom line. Touch controller  713  can receive sense signals (VSENSE)  761  from sense Vcom lines  707  through sense channels  753 . Each sense channel  753  can include a sense amplifier  763  that amplifies sense signals  761 . The amplified sense signals can be further processed by touch controller  713  to determine touches on touch screen  701 . 
     However, applying VGL  735  to gate lines  711  can introduce noise into sense signals  761 . For example, a parasitic gate-to-sense coupling  765  can exist between each gate line  711  and each sense Vcom line  707 . Noise, such as voltage ripples, in VGL  735  can be coupled into sense Vcom lines  707  through gate-to-sense couplings  765 . If the noise occurs while drive signals  757  are being applied and sense signals  761  are being received, the noise can be coupled into the sense signals and amplified by sense amplifier  763 , possibly corrupting touch sensing results. 
       FIG. 8  illustrates an exemplary power management timing method during the touch sensing phase of touch screen device  700  according to various embodiments.  FIG. 8  shows an exemplary timing of BSYNC  723 , TOUCH_CP_EN  751 , VGL_CP_CLK  743 , VGL  735 , VGH_CP_CLK  745 , and VGH  737 .  FIG. 8  also illustrates the output of VCOM MUX I  725 , which can be drive signals  757  during the touch sensing phase. In particular, touch screen  701  can be scanned using multiple touch scan steps  801  in a single touch sensing phase, with one or more drive signals  757  being applied during each touch scan step. During each touch scan step, touch controller  713  can set TOUCH_CP_EN  751  to a low state, such that negative charge pump  719  and positive charge pump  721  are disabled. In other words, the charge pumps can be shut off during active touch sensing, which can help eliminate one source of noise in sense signals  761 , such as voltage ripples in the charge pumps that might have otherwise been coupled into the sense signals. 
     In between touch scan steps  801 , touch controller  713  can suspend the application of drive signals  757 , i.e., suspend active touch sensing, and can set TOUCH_CP_EN  751  to a high state to enable the charge pump clocks and therefore allow the charge pumps to restore VGL  735  and VGH  737  voltage levels, which may have drooped toward ground during touch scanning. It should be understood that the charge pump voltages can still be supplied even during touch scanning. Setting TOUCH_CP_EN  751  to a high state can allow the charge pumps to switch and restore the VGL/VGH voltage levels. In this way, for example, the voltage on gate lines  711  can be maintained at an acceptable level throughout the touch sensing phase by activating the charge pumps during the gaps  803  in between touch scan steps  801  to correct any drops in the voltages on gate lines  711  that may occur while the charge pumps are disabled during the touch scan steps. 
     In this regard, during each gap  803  in between touch scan steps  801 , touch controller  713  can control the negative and/or positive charge pumps, as needed, to apply voltage to the gate lines to maintain desired gate line voltage levels. In the example illustrated in  FIG. 8 , two clock transitions can occur on signal VGL_CP_CLK  743  to the negative charge pump  719  to restore the VGL  735  voltage level that is applied to the gate driver. Likewise, two clock transitions can occur on signal VGH_CP_CLK  745  to restore VGH  737  voltage levels to the gate driver. The number of clock transitions on VGL_CP_CLK  743  and VGH_CP_CLK  745  can be, for example, a function of the load current drawn from VGL  735  and VGH  737 . The voltage levels of VGL  735  and VGH  737  illustrated in  FIG. 8  show how the voltage levels can be affected by periodically clocking negative charge pump  719  and positive charge pump  721 , respectively. Referring to the VGL level, for example, at times when clock transitions on VGL_CP_CLK  743  are not occurring, the voltage level of VGL  735  can droop toward ground and away from the desired voltage level due to, for example, load current imposed on VGL  735  by the gate driver. In some embodiments, touch controller  713  can boost the gate voltages such that the voltage levels of VGL  735  and VGH  737  that are applied during the touch sensing phase are lower than the corresponding voltage magnitudes applied during the display phase. 
     When negative charge pump  719  is clocked by VGL_CP_CLK  743 , the level of VGL  735  and, therefore, the voltage on gate lines can be restored to the VGL_LCM  805  voltage level. Likewise, when positive charge pump  721  is clocked by VGH_CP_CLK  745 , the level of VGH  737  can be restored to the VGH_LCM  807  voltage level. In some cases, noise generated by negative charge pump  719  can affect touch sensing, such as by causing disturbance on the output of the sense amplifier. These disturbances can continue after the charge pump is disabled due to, for example, the finite settling time of the sense amplifier. In some embodiments, post-noise stabilizing can be applied to reduce or eliminate disturbances. For example, sense amplifier disturbances can be reduced or eliminated by shorting the sense amplifier&#39;s feedback network to reset the sense amplifier. 
       FIGS. 9A-9B  illustrate how power is switched through different capacitors according to embodiments of the disclosure. More specifically,  FIGS. 9A and 9B  provide details about how the voltage VGL  735  in  FIG. 7  is generated. Note that similar circuitry (not shown) is used to generate the high voltage level VGH  737  in  FIG. 7 . The circuitry illustrated in  FIGS. 9A and 9B  includes a display capacitor C D    906  and a touch capacitor C T    904 . In the embodiment illustrated in  FIGS. 9A and 9B , C D    906  is permanently coupled between VGL  735  and ground. In contrast, C T    904  has a first terminal coupled to VGL  735  and a second terminal coupled to V AUX    912  which is powered by an auxiliary power supply  908 . The second terminal of C T    904  is also coupled through NFET  902  to ground, and the gate of NFET  902  is coupled to BSYNC signal  723 . 
     The circuitry illustrated in  FIGS. 9A and 9B  generally operates as follows. During the display mode (illustrated in  FIG. 9A ), negative charge pump  910  drives VGL  735  to the display mode voltage VGL_LCM. At the same time, BSYNC signal  723  goes low which causes NFET  902  to decouple the second terminal of C T    904  from ground. During display mode, AUX power  908  charges C T    904  to VGL_DIFF, wherein VGL_DIFF is a voltage difference between the display-mode voltage VGL_LCM and the touch-mode voltage VGL_TOUCH. Because the first terminal of C T    904  is driven to VGL_LCM during the display mode, this causes the voltage difference between the first and second terminals of C T    904  to be set to VGL_TOUCH. 
     During the touch mode (illustrated in  FIG. 9B ), BSYNC signal  723  goes high which causes NFET  902  to couple the second terminal of C T    904  to ground. At the same time, the output of AUX power  908  is tri-stated. Because C T    904  was previously charged to VGL_TOUCH, this causes VGL  735  to rapidly transition to VGL_TOUCH. During touch mode, negative charge pump  910  maintains VGL  735  at VGL_TOUCH. 
       FIG. 10  presents a timing diagram illustrating how power is switched between different voltage levels according to embodiments of the disclosure. More specifically,  FIG. 10  illustrates a transition from display mode (labeled as “LCM Scan”) to touch mode (labeled as “Touch Scan)” and then back to display mode. Some of the operations involved in these transitions are controlled by the BSYNC signal  723  which is at a low voltage level during the display mode and a high voltage level during the touch mode. 
     Charge pump clock signal CP CLK    1002  is active during display mode which allows both negative and positive charge pumps to drive the display mode voltages onto power lines VGL  735  and VGH  737 . However, during touch mode, CP CLK    1002  is only active during intervals where drive signals are suspended to reduce noise problems. Note that drive signals are controlled by the DRV OUT  signal  1004 . 
     V AUX  signal  912  starts at the VGL_DIFF voltage level in display mode, wherein VGL_DIFF is the voltage difference between the low display-mode voltage (VGL_LCM) and the low touch-mode voltage (VGL_TOUCH). Next, when the system enters touch mode, NFET  902  causes V AUX    912  to be pulled to ground. Then, at the end of the touch mode, V AUX    912  returns to VGL_DIFF. 
     The VGH signal  737  is at the VGH_LCM voltage level when the system is in display mode and transitions to VGH_TOUCH when the system enters touch mode. Next, at the end of the touch mode, VGH  737  transitions back to VGH_LCM. Similarly, VGL signal  735  starts in display mode at the VGL_LCM voltage level and transitions to VGL_TOUCH when the system enters touch mode. Next, at the end of the touch mode, VGL  735  transitions back to VGL_LCM. 
     Note that the VGH discharge signal  1006  is active at the start of touch mode when VGH  737  is transitioning from VGH_LCM to VGH_TOUCH. In contrast, the VGH Restore signal  1008  is active at the start of display mode when VGH  737  is transitioning from VGH_TOUCH to VGH_LCM. Similarly, the VGL discharge signal  1010  is active at the start of display mode when VGL  735  is transitioning from VGL_TOUCH to VGL_LCM. 
       FIG. 11A  illustrates an alternative embodiment that selectively switches a power source output between a display-mode capacitor and a touch-mode capacitor according to embodiments of the disclosure. In this way, neither the display-mode capacitor nor the touch-mode capacitor needs to be continually charged and discharged as the output of the power source cycles between display-mode and touch-mode voltages. During display mode, a charge pump maintains a display-mode voltage across the display-mode capacitor. However, the charge pump does not power the display-mode capacitor during touch mode. Note that the voltage on the display-mode capacitor may slightly deviate from the display-mode voltage during touch mode when the display-mode capacitor is not being powered by the charge pump. However, this voltage deviation is corrected when the display-mode capacitor is subsequently powered by the charge pump when the system returns to display mode. Similarly, the charge pump maintains a touch-mode voltage across a touch-mode capacitor during touch mode, but does not power the touch-mode capacitor during display mode. 
     Referring to the top of  FIG. 11A , a positive charge pump  1120  drives VGH  737 , which is coupled through a number of capacitors  1104 ,  1106  and  1108  to ground. More specifically, VGH  737  is coupled to a first terminal of C HD    1104 , wherein C HD    1104  holds the VGH display-mode voltage. The second terminal of C HD    1104  is coupled through PFET  1102  to ground. The gate of PFET  1102  is coupled to the positive BSYNC signal BSYNC P    1101 . In this way, when BSYNC P    1101  is asserted during display mode, C HD    1104  is coupled between VGH  737  and ground. VGH  737  is also coupled to a first terminal of C HT    1106 , wherein C HT    1106  holds the VGH touch-mode voltage. The second terminal of C HT    1106  is coupled through PFET  1107  to ground. Also, the gate of PFET  1107  is coupled to the BSYNC N    1102 , which is the negative BSYNC signal. In this way, when BSYNC N    1102  is asserted during touch mode, C HT    1106  is coupled between VGH  737  and ground. VGH  737  is also coupled through a parasitic capacitance C HP    1108  to ground, wherein C HP    1108  is associated with various touch panel parasitics. 
     Referring to the bottom of  FIG. 11A , a negative charge pump  1119  drives VGL signal  735 , which is coupled through a number of capacitors  1114 ,  1116  and  1118  to ground. More specifically, VGL  735  is coupled to a first terminal of C LD    1114 , wherein C LD    1114  holds the VGL display-mode mode voltage. The second terminal of C LD    1114  is coupled through NFET  1112  to ground. The gate of NFET  1112  is coupled to BSYNC N  signal  1102  which is the negative BSYNC signal. In this way, when BSYNC N  signal  1102  is asserted during display mode, C LD    1114  is coupled between VGL  735  and ground. VGL  735  is also coupled to a first terminal of C LT    1116 , wherein C LT    1116  holds the touch-mode VGL voltage. The second terminal of C LT    1116  is coupled through NFET  1117  to ground. The gate of NFET  1117  is coupled to the positive BSYNC signal BSYNC P    1101 . In this way, when BSYNC P    1101  is asserted during touch mode, C LT    1116  is coupled between VGL  735  and ground. Finally, VGL  735  is coupled through a parasitic capacitor C LP    1118  to ground, wherein C LP    1118  is associated with various touch panel parasitics. 
     Note that the PFET  1102 , PFET  1107 , NFET  1112 , and NFET  1117  illustrated in  FIG. 11A  include body diodes which facilitate charging of the FETs to initial voltages during system startup. 
       FIG. 11B  presents a timing diagram for BSYNC P  signal  1101  and BSYNC N  signal  1102  for the circuit illustrated in  FIG. 11A  according to embodiments of the disclosure. More specifically,  FIG. 11B  illustrates how the BSYNC P  signal  1101  and BSYNC N  signal  1102  change as the system cycles between touch mode and display mode. At the beginning of the timing diagram, the system is initially in display mode wherein BSYNC P  signal  1101  is at the negative supply voltage −5.7V and BSYNC N  signal  1102  is at the positive supply voltage 5.7V. Next, at the start of touch mode, both BSYNC P  signal  1101  and BSYNC N  signal  1102  briefly enter a tristate period wherein both signals are effectively at zero volts. After this brief tristate period, BSYNC P  signal  1101  rises to the positive supply voltage 5.7V and BSYNC N  signal  1102  falls to the negative supply voltage  1107  −5.7V. Then, at the start of display mode, BSYNC P  signal  1101  and BSYNC N  signal  1102  again briefly enter a tristate period and then BSYNC P  signal  1101  falls to the negative supply voltage −5.7V and BSYNC N  signal  1102  rises to the positive supply voltage 5.7V. 
     Alternative Embodiments 
       FIG. 12A  illustrates an alternative embodiment that uses NFET transistors according to embodiments of the disclosure. This embodiment is similar to the embodiment illustrated in  FIG. 11A , except that PFET transistors  1102  and  1107  are replaced with NFET transistors  1202  and  1207 . Also, because of the associated change in transistor polarity, the gate of NFET transistor N 0 H  1202  is coupled to BSYNC N  signal  1102  and the gate of NFET transistor N 1 H  1207  is coupled to BSYNC P  signal  1101 . Note that  FIG. 12A  also illustrates the body diodes for the NFET transistors  1202 ,  1207 ,  1212  and  1217 . These body diodes can be used to precharge the capacitors which are coupled to VGH  737  and VGL  735 . 
       FIG. 12B  presents a timing diagram for the embodiment illustrated in  FIG. 12A  according to embodiments of the disclosure. Note that the system provides two supply voltages 1.8V and 5.7V. In the power-up time interval T 0 , the 1.8V supply is activated first and the 5.7 V supply is not yet available yet. In this situation, the 1.8V supply is used to precharge the capacitors. More specifically, during time interval T 0 , BSYNC signal  1240  is low and both BSYNC N  signal  1102  and BSYNC P  signal  1101  are at 1.8V. In this case, all of the NFET transistors N 0 H  1202 , N 1 H  1207 , N 0 L  1212  and N 1 L  1217  are turned on to precharge capacitors C HD    1104 , C HT    1106 , C HP    1108 , C LD    1114 , C LT    1116 , and C LP    1118 . 
     Next, at the start of a first frame during time interval T 1 , BSYNC signal  1240  remains low, BSYNC N  signal  1102  rises to 5.7V and BSYNC P  signal  1101  falls to −5.7V. In this situation, transistors N 0 H  1202  and N 0 L  1212  remain on, but transistors N 1 H  1207  and N 1 L  1217  are turned off. 
     Next, during time interval T 3 , BSYNC signal  1240  goes high, BSYNC N  signal  1102  falls to −5.7V and BSYNC P  signal  1101  remains at −5.7V. In this case, all transistors N 0 H  1202 , N 0 L  1212 , N 1 H  1207  and N 1 L  1217  are turned off. 
     Next, during time interval T 2 , BSYNC signal  1240  remains high, BSYNC N  signal  1102  remains low at −5.7V and BSYNC P  signal  1101  rises to 5.7V. In this case, transistors N 0 H  1202  and N 0 L  1212  are turned off and transistors N 1 H  1207  and N 1 L  1217  are turned on. 
     Then, during time interval T 4 , BSYNC signal  1240  goes low, BSYNC N  signal  1102  remains at −5.7V and BSYNC P  signal  1101  falls to −5.7V. In this case, transistors N 0 H  1202  and N 0 L  1212  remain off and transistors N 1 H  1207  and N 1 L  1217  are turned off. 
     At the end of T 4 , the system returns to T 1  for the next frame. The system then cycles through T 1 , T 3 , T 2  and T 4  for a number of frames. Finally, after the last frame is complete, during the power-down time interval T 5 , the 5.7V supply turns off first while the 1.8V supply remains on. During this time interval, the 1.8V supply is used to turn the FETs so the capacitors can be discharged. More specifically, BSYNC signal  1240  remains low, and both BSYNC N  signal  1102  and BSYNC P  signal  1101  rise to 1.8V to turn on FETs  1202 ,  1207 ,  1212  and  1217 . 
       FIG. 13A  illustrates a variation of this alternative embodiment that uses NFET and PFET transistors according to embodiments of the disclosure. This embodiment is similar to the embodiment illustrated in  FIG. 12A , except that NFET transistors  1202  and  1207  have been replaced with PFET transistors  1202  and  1207 .  FIG. 13B  presents a timing diagram for the embodiment illustrated in  FIG. 13A  according to embodiments of the disclosure. This timing diagram is similar to the timing diagram illustrated in  FIG. 12B , except that the voltage levels for BSYNC N  signal  1102  are essentially reversed to perform the same functional operations. More specifically, BSYNC N  signal  1102  starts out at 0V in T 0 , falls to −5.7V in T 1 , rises to 5.7V in T 3 , remains at 5.7V in both T 2  and T 4  and then returns to 0V in T 5 . 
       FIG. 14A  illustrates another embodiment that uses NFET transistors without body diode conduction according to embodiments of the disclosure. In this case, each FET  1402 ,  1407 ,  1412  and  1417  is actually 2 FETs connected in series, with body diodes connected back-to-back, to eliminate substrate diode conduction and to avoid any coupling to VGH  737  or VGL  735 , which can potentially cause voltage errors in the capacitors. 
     In this embodiment, the FETs are all in a defined state prior to the 5.7V supply, VGH and VGL being active (startup condition), without having to rely on the FET body diodes to pre-charge the VGH and VGL capacitors  1104 ,  1106 ,  1108 ,  1114 ,  116  and  1118 . Note that the 1.8V supply is typically applied prior to 5.7V supply because it powers the touch/display logic. In order to put the FETs  1402 ,  1407 ,  1412  and  1417  in a defined state, BSYNC N  signal  1102  and BSYNC P  signal  1101  can be driven from the 1.8V domain to turn on the FETs to allow pre-charging of the VGL/VGH capacitors. 
       FIG. 14B  presents a timing diagram for the embodiment illustrated in  FIG. 14A  according to embodiments of the disclosure. Note that this timing diagram is essentially the same as the timing diagram illustrated in  FIG. 12B . 
     The foregoing descriptions of embodiments have been presented for purposes of illustration and description only. They are not intended to be exhaustive or to limit the present description to the forms disclosed. Accordingly, many modifications and variations will be apparent to practitioners skilled in the art. Additionally, the above disclosure is not intended to limit the present description. The scope of the present description is defined by the appended claims.

Metadata:
Filing Date: 20150908
Publication Date: 20180807
Grant Date: 20180807
Priority Date: 20120608
Inventors: KRAH, CHRISTOPH H.
BI, YAFEI
WHITE, KEVIN J.
Assignee: APPLE INC
CPC Classifications: [{"code": "G06F3/041", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0412", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/041", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0416", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/044", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0412", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/0446", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/04166", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0412", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/0446", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/04166", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 48670776