PATENT DOCUMENT

Publication Number: US-9760195-B2
Application Number: US-201113244072-A
Country: US
Kind Code: B2

Title: Power management for integrated touch screens

Abstract:
Reducing or eliminating the effects of noise that can be generated by a power system of a touch screen device, such as a gate line voltage system that applies voltage to gate lines of the touch screen, is provided. In one example, a power supply, such as a charge pump, can be disabled during active touch sensing, such that noise from the charge pump is not generated during touch sensing. In some examples, a voltage regulator can help to maintain the gate voltage level at or above a desired threshold. In some cases, noise entering the touch sensing system can have a lasting effect on noise-sensitive components, even after the noise source is disabled. In these cases, a post-noise stabilizing system can be included to stabilize, reset, etc., noise-sensitive components of the touch sensing system, which can help to reduce or eliminate the lasting effect of noise.

Claims:
What is claimed is: 
     
       1. An integrated touch screen system comprising:
 a touch screen including a plurality of display pixels, the plurality of display pixels including an addressing system that includes a plurality of conductive lines; 
 a voltage regulator; 
 a driver configured to receive first voltages from the voltage regulator and apply second voltages to the conductive lines based on the received first voltages, the first voltages having a stable level; 
 a display system that updates an image displayed by the display pixels during a display phase, wherein the updating of the image includes actively operating a power supply to apply third voltages to the voltage regulator, and operating the driver to apply the second voltages to the conductive lines to address the display pixels; and 
 a touch sensing system that senses touch during a touch sensing phase, the touch sensing phase including a plurality of active sensing periods during which the touch sensing system performs active touch sensing while the power supply is not actively applying the third voltages to the voltage regulator, the touch sensing phase further including at least one gap period between active sensing periods, wherein the power supply is actively operated to apply the third voltages to the voltage regulator, and the driver is operated to apply the second voltages to the conductive lines during the at least one gap period while active touch sensing is not being performed, wherein the power supply applies the third voltages during the one or more gap periods such that the voltage regulator is able to apply the first voltages to the driver during the active sensing periods. 
 
     
     
       2. The integrated touch screen system of  claim 1 , wherein each display pixel includes a pixel thin-film transistor (TFT), and the conductive lines include gate lines, each pixel TFT being connected to one gate line. 
     
     
       3. The integrated touch screen system of  claim 1 , wherein the power supply includes one of a charge pump and an inductive boost regulator. 
     
     
       4. The integrated touch screen system of  claim 1 , wherein the display system controls the power supply to apply the third voltages to the voltage regulator during at least part of the display phase, and the touch sensing system controls the power supply to apply the third voltages to the voltage regulator during at least part of the touch sensing phase. 
     
     
       5. The integrated touch screen system of  claim 1 , further comprising:
 a voltage boost system that boosts the third voltages applied by the power supply during the touch sensing phase, such that a magnitude of the third voltages applied to the voltage regulator during the touch sensing phase is greater than the magnitude of the third voltages applied to the voltage regulator during the display phase. 
 
     
     
       6. The integrated touch screen system of  claim 1 , wherein an output voltage level of the power supply is based on a first reference voltage during the display phase, and the output voltage level of the power supply is based on a second reference voltage during the at least one gap period. 
     
     
       7. The integrated touch screen system of  claim 1 , wherein an output voltage level of the power supply is based on a first reference voltage during the display phase, the output voltage level of the power supply is based on a second reference voltage during the at least one gap period, an output voltage level of the voltage regulator is based on a third reference voltage during the display phase, and the output voltage level of the voltage regulator is based on a fourth reference voltage during the at least one gap period. 
     
     
       8. The integrated touch screen system of  claim 1 , wherein the power supply applies the third voltages to the voltage regulator during a first portion of the at least one gap period, the touch sensing system including a plurality of drive lines that are stimulated with drive signals during the active sensing periods, and a sense amplifier that receives a sense signal corresponding to the one or more drive signals, the integrated touch screen system further comprising: a post-noise stabilization system that resets the sense amplifier during a second portion of the at least one gap period, the second portion being after the first portion. 
     
     
       9. The integrated touch screen system of  claim 8 , wherein the post-noise stabilization system includes a switch connected to a feedback loop of the sense amplifier, and wherein resetting the sense amplifier includes closing the switch to short the feedback loop. 
     
     
       10. A method of managing power in a touch screen system that includes a touch screen including a plurality of display pixels, the plurality of display pixels including an addressing system that includes a plurality of conductive lines, the integrated touch screen system further comprising a driver configured to receive first voltages from a voltage regulator and apply second voltages to the conductive lines based on the received first voltages, the first voltages having a stable level, the method comprising:
 updating an image displayed by the display pixels during a display phase, wherein the updating of the image includes actively operating a power supply to apply third voltages to the voltage regulator, and operating the driver to apply second voltages to the conductive lines to address the display pixels; and 
 sensing touch during a touch sensing phase, the touch sensing phase including a plurality of active sensing periods during which the touch sensing system performs active touch sensing while the power supply is not actively applying the third voltages to the voltage regulator, the touch sensing phase further including at least one gap period between active sensing periods, wherein the power supply is actively operated to apply the third voltages to the voltage regulator, and the driver is operated to apply the second voltages to the conductive lines during the at least one gap period while active touch sensing is not being performed, wherein the power supply applies the third voltages during the one or more gap periods such that the voltage regulator is able to apply the first voltages to the driver during the active sensing periods. 
 
     
     
       11. The method of  claim 10 , wherein a display system controls the power supply to apply the third voltages to the voltage regulator during at least part of the display phase, and a touch sensing system controls the power supply to apply the third voltages to the voltage regulator during at least part of the touch sensing phase, the method further comprising:
 generating a synchronization signal between the display system and the touch sensing system, wherein the control of the power supply is based on the synchronization signal. 
 
     
     
       12. The method of  claim 10 , further comprising:
 boosting the third voltages applied by the power supply during the touch sensing phase, such that the magnitude of the third voltages applied to the voltage regulator during the touch sensing phase is greater than the magnitude of the third voltages applied to the voltage regulator during the display phase. 
 
     
     
       13. The method of  claim 10 , wherein an output voltage level of the power supply is based on a first reference voltage during the display phase, and the output voltage level of the power supply is based on a second reference voltage during the at least one gap period. 
     
     
       14. The method of  claim 10 ,
 wherein an output voltage level of the power supply is based on a first reference voltage during the display phase, the output voltage level of the power supply is based on a second reference voltage during the at least one gap period, an output voltage level of the voltage regulator is based on a third reference voltage during the display phase, and the output voltage level of the voltage regulator is based on a fourth reference voltage during the at least one gap period. 
 
     
     
       15. The method of  claim 10 , wherein the touch screen system includes a touch sensing system including a plurality of drive lines that are stimulated with drive signals during the active sensing periods, and a sense amplifier that receives a sense signal corresponding to one or more drive signals, and wherein applying the third voltages during the at least one gap period includes applying the third voltages during a first portion of the at least one gap period, the method further comprising:
 resetting the sense amplifier during a second portion of the at least one gap period, the second portion being after the first portion. 
 
     
     
       16. The method of  claim 15 , wherein resetting the sense amplifier includes shorting a feedback loop of the sense amplifier. 
     
     
       17. An integrated touch screen system comprising:
 a touch screen including a plurality of display pixels, the plurality of display pixels including an addressing system that includes a plurality of conductive lines; 
 a voltage regulator; 
 a capacitor coupled to an input of the voltage regulator; 
 a driver configured to receive first voltages from the voltage regulator and apply second voltages to the conductive lines based on the received first voltages, the first voltages having a stable level; 
 a display system that updates an image displayed by the display pixels during a display phase, wherein the updating of the image includes actively operating a power supply to apply third voltages to the voltage regulator, and operating the driver to apply the second voltages to the conductive lines to address the display pixels; and 
 a touch sensing system that senses touch during a touch sensing phase, the touch sensing phase including a plurality of active sensing periods during which the touch sensing system performs active touch sensing while the power supply is not actively applying the third voltages to the voltage regulator, the touch sensing phase further including at least one gap period between active sensing periods, wherein the power supply is actively operated to apply the third voltages to the voltage regulator, and the driver is operated to apply the second voltages to the conductive lines during the at least one gap period while active touch sensing is not being performed, wherein the capacitor is charged while the power supply is actively operated to apply the third voltages, and the charge is transferred from the capacitor to the input of the voltage regulator during the touch phase while the power supply is not actively applying third voltages. 
 
     
     
       18. The integrated touch screen system of  claim 17 , wherein each display pixel includes a pixel thin-film transistor (TFT), and the conductive lines include gate lines, each pixel TFT being connected to one gate line. 
     
     
       19. The integrated touch screen system of  claim 17 , wherein the power supply includes one of a charge pump and an inductive boost regulator. 
     
     
       20. The integrated touch screen system of  claim 17 , wherein the display system controls the power supply to apply the third voltages to the voltage regulator during at least part of the display phase, and the touch sensing system controls the power supply to apply the third voltages to the voltage regulator during at least part of the touch sensing phase. 
     
     
       21. The integrated touch screen system of  claim 17 , further comprising:
 a voltage boost system that boosts the third voltages applied by the power supply during the touch sensing phase, such that a magnitude of the third voltages applied to the voltage regulator during the touch sensing phase is greater than the magnitude of the third voltages applied to the voltage regulator during the display phase. 
 
     
     
       22. The integrated touch screen system of  claim 17 , wherein an output voltage level of the power supply is based on a first reference voltage during the display phase, and the output voltage level of the power supply is based on a second reference voltage during the at least one gap period. 
     
     
       23. The integrated touch screen system of  claim 17 , wherein an output voltage level of the power supply is based on a first reference voltage during the display phase, the output voltage level of the power supply is based on a second reference voltage during the at least one gap period, an output voltage level of the voltage regulator is based on a third reference voltage during the display phase, and the output voltage level of the voltage regulator is based on a fourth reference voltage during the at least one gap period. 
     
     
       24. The integrated touch screen system of  claim 17 , wherein the power supply applies the third voltages to the voltage regulator during a first portion of the at least one gap period, the touch sensing system including a plurality of drive lines that are stimulated with drive signals during the active sensing periods, and a sense amplifier that receives a sense signal corresponding to the one or more drive signals, the integrated touch screen system further comprising: a post-noise stabilization system that resets the sense amplifier during a second portion of the at least one gap period, the second portion being after the first portion. 
     
     
       25. The integrated touch screen system of  claim 24 , wherein the post-noise stabilization system includes a switch connected to a feedback loop of the sense amplifier, and wherein resetting the sense amplifier includes closing the switch to short the feedback loop. 
     
     
       26. A method of managing power in a touch screen system that includes a touch screen including a plurality of display pixels, the plurality of display pixels including an addressing system that includes a plurality of conductive lines, the integrated touch screen system further comprising a driver configured to receive first voltages from a voltage regulator and apply second voltages to the conductive lines based on the received first voltages, the first voltages having a stable level, the method comprising:
 updating an image displayed by the display pixels during a display phase, wherein the updating of the image includes actively operating a power supply to apply third voltages to the voltage regulator, and operating the driver to apply second voltages to the conductive lines to address the display pixels; and 
 sensing touch during a touch sensing phase, the touch sensing phase including a plurality of active sensing periods during which the touch sensing system performs active touch sensing while the power supply is not actively applying the third voltages to the voltage regulator, the touch sensing phase further including at least one gap period between active sensing periods, wherein the power supply is actively operated to apply the third voltages to the voltage regulator, and the driver is operated to apply the second voltages to the conductive lines during the at least one gap period while active touch sensing is not being performed, wherein a capacitor coupled to the input of the voltage regulator is charged while the power supply is actively operated to apply the third voltages, and the charge is transferred from the capacitor to the input of the voltage regulator during the touch phase while the power supply is not actively applying third voltages. 
 
     
     
       27. The method of  claim 26 , wherein a display system controls the power supply to apply the third voltages to the voltage regulator during at least part of the display phase, and a touch sensing system controls the power supply to apply the third voltages to the voltage regulator during at least part of the touch sensing phase, the method further comprising:
 generating a synchronization signal between the display system and the touch sensing system, wherein the control of the power supply is based on the synchronization signal. 
 
     
     
       28. The method of  claim 26 , further comprising:
 boosting the third voltages applied by the power supply during the touch sensing phase, such that the magnitude of the third voltages applied to the voltage regulator during the touch sensing phase is greater than the magnitude of the third voltages applied to the voltage regulator during the display phase. 
 
     
     
       29. The method of  claim 26 , wherein an output voltage level of the power supply is based on a first reference voltage during the display phase, and the output voltage level of the power supply is based on a second reference voltage during the at least one gap period. 
     
     
       30. The method of  claim 26 , wherein an output voltage level of the power supply is based on a first reference voltage during the display phase, the output voltage level of the power supply is based on a second reference voltage during the at least one gap period, an output voltage level of the voltage regulator is based on a third reference voltage during the display phase, and the output voltage level of the voltage regulator is based on a fourth reference voltage during the at least one gap period. 
     
     
       31. The method of  claim 26 , wherein the touch screen system includes a touch sensing system including a plurality of drive lines that are stimulated with drive signals during the active sensing periods, and a sense amplifier that receives a sense signal corresponding to one or more drive signals, and wherein applying the third voltages during the at least one gap period includes applying the third voltages during a first portion of the at least one gap period, the method further comprising:
 resetting the sense amplifier during a second portion of the at least one gap period, the second portion being after the first portion. 
 
     
     
       32. The method of  claim 31 , wherein resetting the sense amplifier includes shorting a feedback loop of the sense amplifier.

Description:
FIELD OF THE DISCLOSURE 
     This relates generally to touch sensing, and more particularly, to power management for integrated display touch controllers. 
     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 near 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). 
     SUMMARY 
     The following description includes examples of reducing or eliminating the effects of noise that can be generated by a power system of a touch screen device, such as a gate line voltage system that applies voltage to gate lines of the touch screen. In one example, a power supply, such as a charge pump, can be disabled during active touch sensing, such that noise from the charge pump is not generated during touch sensing. In some examples, a voltage regulator can help to maintain the gate voltage level at or above a desired threshold. Some examples can include a voltage boost system that can increase the magnitude of the voltage applied to the gate lines during the touch sensing phase, which can help maintain the gate voltage level during the touch sensing phase. In some cases, noise entering the touch sensing system can have a lasting effect on noise-sensitive components, even after the noise source is disabled, for example. In these cases, for example, a post-noise stabilizing system can be included to stabilize, reset, etc., noise-sensitive components of the touch sensing system, which can help to reduce or eliminate the lasting effect of noise. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A-1C  illustrate an example mobile telephone, an example media player, and an example personal computer that each include an example touch screen according to embodiments of the disclosure. 
         FIG. 2  is a block diagram of an example computing system that illustrates one implementation of an example touch screen according to embodiments of the disclosure. 
         FIG. 3  is a more detailed view of the touch screen of  FIG. 2  showing an example configuration of drive lines and sense lines according to embodiments of the disclosure. 
         FIG. 4  illustrates an example configuration in which touch sensing circuitry includes common electrodes (Vcom) according to embodiments of the disclosure. 
         FIG. 5  illustrates an exploded view of example display pixel stackups according to embodiments of the disclosure. 
         FIG. 6  illustrates an example touch sensing operation according to embodiments of the disclosure. 
         FIG. 7  illustrates an example touch screen device according to various embodiments. 
         FIG. 8  illustrates an example power management method of a touch sensing system according to various embodiments. 
         FIG. 9  is a diagram of circuit portion of an example touch screen device according to various embodiments. 
         FIG. 10  is a flowchart of an example operation of a touch screen device according to various embodiments. 
         FIG. 11  illustrates more details of an example touch sensing phase operation of a touch screen device according to various embodiments. 
         FIGS. 12A and 12B  illustrate an example transition from display phase to touch phase and an example transition from touch phase to display phase according to various embodiments. 
         FIG. 13  shows an example timing diagram for an example charge and discharge process according to various embodiments. 
         FIG. 14  illustrates an example power management method of a touch sensing system according to various embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description of example embodiments, reference is made to the accompanying drawings which form a part hereof, and in which it is shown by way of illustration specific embodiments in which embodiments of the disclosure can be practiced. It is to be understood that other embodiments can be used and structural changes can be made without departing from the scope of the embodiments of this disclosure. 
     The following description includes examples of reducing or eliminating the effects of noise that can be generated by a power system of a touch screen device, such as a gate line voltage system that applies voltage to gate lines of the touch screen. In one example, a power supply, such as a charge pump, can be disabled during active touch sensing, such that noise from the charge pump is not generated during touch sensing. In some examples, a voltage regulator can help to maintain the gate voltage level at or above a desired threshold. Some examples can include a voltage boost system that can increase the magnitude of the voltage applied to the gate lines during the touch sensing phase, which can help maintain the gate voltage level during the touch sensing phase. In some cases, noise entering the touch sensing system can have a lasting effect on noise-sensitive components, even after the noise source is disabled, for example. In these cases, for example, a post-noise stabilizing system can be included to stabilize, reset, etc., noise-sensitive components of the touch sensing system, which can help to reduce or eliminate the lasting effect of noise. 
     As touch sensing circuitry becomes more closely integrated with circuitry of other systems, undesirable interaction between circuit elements of different systems can be more likely to occur. For example, touch sensing circuitry can be integrated into the display pixel stackups of integrated touch screens. Display pixel stackups are typically manufactured by processes including depositing, masking, etching, doping, etc., of materials such as conductive materials (e.g., metal, substantially transparent conductors), semiconductive materials (e.g., polycrystalline silicon (Poly-Si)), and dielectric materials (e.g., SiO2, organic materials, SiNx). Various elements formed within a display pixel stackup can operate as circuitry of the display system to generate an image on the display, while other elements can operate as circuitry of a touch sensing system that senses one or more touches on or near the display. 
       FIGS. 1A-1C  show example systems in which a touch screen according to embodiments 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 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 example computing system  200  that illustrates one implementation of an example 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 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 a 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 example 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 example integrated touch screen in which embodiments of the disclosure can be implemented with 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 embodiments 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. 
     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 example 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 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 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 example 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 example 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 example 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 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 (M1) layer  501 , a second metal (M2) layer  503 , a common electrode (Vcom) layer  505 , and a third metal (M3) 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 . M3 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. M1 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 M1 layer can also include gate lines  520 . M2 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 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 example 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 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. 
     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 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 example touch screen device  700  and an example 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 on 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 through 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 example configuration, subsequent voltage regulators, such as low dropout regulators (LDOs), can be used to stabilize VGL and/or VGH rails. In this example 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 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 example 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 example 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 through 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 example power management timing method during the touch sensing phase of touch screen device  700  according to various embodiments.  FIG. 8  shows an example 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 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 to a high state to enable the charge pump clocks and therefore allow the charge pumps to restore VGL and VGH 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, and that the charge pump voltages may have drooped toward ground during touch scanning. Setting TOUCH_CP_EN to a high state can allow 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 and VGH_CP_CLK can be, for example, a function of the load current drawn from VGL and VGH. 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 are not occurring the voltage level of VGL can droop toward ground and away from the desired voltage level due to, for example, load current imposed on VGL 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. In some embodiments, touch controller  713  can boost the gate voltages such that the magnitudes of the voltage levels of VGL  735  and VGH  737  that are applied during the touch sensing phase are greater than the corresponding voltage magnitudes applied during the display phase, as illustrated in  FIG. 14 . 
     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 VGL_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. 
       FIG. 9  is a more detailed diagram of circuit portion of an example touch screen device  900  according to various embodiments of the disclosure. The circuit portion of touch screen device  900  illustrates elements of a noise coupling mechanism, such as described above, that can couple noise on the gate lines into the touch sensing system. For the sake of clarity, other elements of touch screen device  900  have been omitted from  FIG. 9 . Touch screen device  900  can include a touch screen controller  901  that can be, for example, a combined touch and display controller, such as touch screen controller  703  above. Touch screen controller  901  can include a negative charge pump  902 , a voltage regulator, such as a negative low dropout regulator (LDO)  903 , which can keep a gate line voltage (VGL)  905  level stable regardless of the state of the charge pump. Negative charge pump  902  can have an output capacitor Cvcpl  908 , which can be connected to a ground  910 . During touch scanning, an output voltage of the negative charge pump (VCPL)  912  can droop toward ground due to the gate drivers sinking current into Cvcpl  908 . The amount of droop can be dependent on the magnitude of the load current. In between touch scans, negative charge pump  902  can be enabled and can restore the VCPL  912  level to a desired charge pump voltage level for the touch phase, VCPL_TOUCH. The LDO can be powered by VCPL  912  and can provide a stable output voltage VGL, which can equal the VGL_TOUCH voltage level, while rejecting the noise on VCPL. Vcpl_ref  914  can be the reference voltage for negative charge pump  902  and can control the VCPL  912  voltage level. Vgl_ref  916  can be the reference voltage for negative LDO  903  and can control the VGL  905  voltage level. Vcpl_ref  914  can be adjusted such that the negative charge pump voltage level VCPL  912  is above the VGL  905  voltage level such that negative LDO  903  remains in regulation. The difference between VCPL  912  and VGL  905 , that is, the difference between the voltage into negative LDO  903  and the output voltage of the negative LDO, can be dependent on the minimum dropout voltage requirement Vdo_ldo for the negative LDO, the charge pump inactivity Tcp_off and the VGL supply current Ivgl. The difference between VCPL  912  and VGL  905  is referred to as over voltage (Vdo) and is defined as:
 
 Vdo=Vdo _ ldo+Ivgl*Tcp _off/ Cvcpl.  
 
The last term in the equation is the amount of voltage change across Cvcpl  908  due to current into the output capacitor from the gate drivers.
 
     Touch screen controller  901  can also include a sense amplifier  906  that can include a feedback resistor (RFB)  907  and a feedback capacitor (CFB)  909 . Touch screen controller  901  can include a post-noise stabilizing system  910  that can include a feedback bypass switch (SW)  911 , which can be connected in parallel with feedback resistor  907  and feedback capacitor  909 , and a feedback bypass controller (FBK_BP)  913  that can control feedback bypass switch  911  to short the feedback loop of sense amplifier  906 , as described in more detail below. In some embodiments, feedback bypass controller  913  can be included in a touch controller (not shown) of touch screen controller  901 , for example. 
       FIG. 9  shows some elements of a touch screen of touch screen device  900 , including a gate line  915  and a sense line  917 . Sense line  917  can include, for example, a sense Vcom line, such as described above in reference to  FIG. 7 . A gate-to-sense coupling capacitance  919  between gate line  915  and sense line  917  can couple noise  920  on the gate line, such as noise from negative LDO  903 , into the sense line. Gate-to-sense coupling capacitance  919  can result from, for example, the structural configuration and material composition of gate line  915  and sense line  917 , the structures and materials of other circuit structures, the particular mode of operation of one or more circuit elements of the touch screen device, etc.  FIG. 9  also shows an external noise source  921 , which can generate external noise that can be coupled into sense line  917  by an external noise coupling capacitance  922 . 
     The noise, Vnz_o, on the output of the sense amplifier due to the noise, Vnz, on VGL coupled through the gate-to-sense line capacitance, Cvs, into the sense amplifier can be defined as: Vnz_o=Vnz*Gvs. Gvs is the noise gain of the sense amplifier from VGL to the output of the sense amplifier and is defined as: Gvs=−Cvs/Cfb. Vnz_o can include in-band components, i.e., that occur within the demodulation bandwidth of the touch subsystem, and/or include out-of-band components. Out-of-band noise components can be detrimental to touch performance and can take up dynamic output range in the sense amplifier, therefore limiting the amount of external noise the sense amplifier can accommodate. For example, the sense amplifier can have a dynamic output range of 4 Vpp. The touch signal can take up 1 Vpp, and therefore can occupy 25% of the sense amplifier output range. This can leave 75% of the sense amplifier&#39;s output range for external noise. Thus, for example, if the noise gain, Gvs, is 25V/V and the residual noise on VGL is 40 mV, the VGL noise component would take up (25V/V×0.04 Vpp)=1 Vpp in the output of the sense amplifier, therefore reducing the sense amplifier&#39;s output range for external noise from 75% to 50%. It is therefore beneficial to utilize LDO  903  to reduce any noise induced by the charge pump. 
     When negative charge pump  902  is off, external noise source  921  and LDO  903  may be the sole source of noise into the sense amplifier due to gate-to-sense coupling capacitance Cvs  919 . However, while negative charge pump  902  is operating (as illustrated in  FIG. 9 ), sense line noise  923  can also include residual charge pump noise, due to finite power supply rejection of LDO, for example. 
     As explained above, the VGL voltage levels during touch phase and display phase can be different. In some embodiments, it can be advantageous to lower the VGL voltage level during touch phase, which can reduce or eliminate cross talk between the display system and the touch sensing system. In order to increase touch integration time (i.e., reducing integration bandwidth and therefore increasing touch signal-to-noise ratio), it can be advantageous to reduce the time it takes for the VGL voltage level to settle from VGL_LCM to VGL_TOUCH after entering touch phase upon the rising edge of BSYNC, where VGL_LCM is the VGL voltage level during display phase and VGL_TOUCH is the VGL voltage level during touch phase. Typically, the charge pump settling time can be longer than the duration of touch phase and therefore may greatly exceed the settling time needed to charge VGL from VGL_LCM to VGL_TOUCH in the desired time. Therefore, it can be advantageous to rely on the charge transfer from Cvcpl  908  to an LDO output capacitor Cvgl  925  to quickly charge Cvgl to the VGL_TOUCH voltage level. 
       FIGS. 12A and 12B  show a more detailed view of example negative LDO  903  and the current flow out of and into Cvgl  925  during transition from display phase to touch phase (illustrated in  FIG. 12A ) and transition from touch phase to display phase (illustrated in  FIG. 12B ) according to various embodiments. Negative LDO  903  can have a push-pull output stage  1201  including of a P-channel FET (field effect transistor)  1203  and an N-channel FET  1205 . The gain of negative LDO  903  can be set by a feedback network including an input resistor Ri  1207  and a feedback resistor Rf  1209 . In this example, the output voltage of the negative LDO is: VGL=−Vgl_ref*Rf/Ri. 
     Referring now to  FIG. 12A , during the transition from display phase to touch phase, Vgl_ref  916  can transition from a first voltage level to a second voltage level, where the second voltage level can typically be higher than the first voltage level. This can cause N-channel FET  1205  in push-pull output stage  1201  to conduct, which can result in charge being transferred from Cvgl  925  to Cvcpl  908  (indicated in  FIG. 12A  by arrowed lines along the path from Cvgl to Cvcpl), therefore lowering the VGL voltage level from VGL_LCM to VGL_TOUCH. In order to maintain a touch drop-out voltage requirement, Vdo_touch, charge pump reference voltage Vcpl_ref  914  can be adjusted accordingly. A settling time, Tsettle, (described in more detail below in reference to  FIG. 13 ) can depend on the sizes of capacitors Cvgl  925  and Cvcpl  908 , the amount of overcharge Vdo, and the ON resistance, RON, of N-channel FET  1205 . In some embodiments, two parallel N-channel FETs can be used, a first N-channel FET that can be always active and a second N-channel FET that can be enabled only during the settling phase during the transition from touch phase to display phase. The second N-channel FET can be used to lower the impedance between Cvgl and Cvcpl as to speed up settling of VGL to the VGL_TOUCH voltage level upon transition from the display phase to the touch phase. 
     Referring to  FIG. 12B , during the transition from touch phase to display phase, Vgl_ref  916  can transition from a first voltage level, VGL_TOUCH, to a second voltage level, VGL_LCM, where the second voltage level can typically be higher than the first voltage level. This can cause P-channel FET  1203  in push-pull output stage  1201  of negative LDO  903  to conduct, which can result in charge being transferred from ground to Cvgl  925  (indicated in  FIG. 12B  by arrowed lines along the path from ground to Cvgl). In order to maintain a LDO drop-out requirement, Vdo_lcm, the charge pump reference voltage Vcpl_ref  914  can be adjusted accordingly. In this example embodiment, the settling time can be largely dependent on Cvgl  925  and the ON resistance of P-channel FET  1203 . 
       FIG. 13  shows an example timing diagram for an example VGL charge and discharge process according to various embodiments. Upon rising edge of a BSYNC signal  1301 , a charge pump reference voltage, Vcpl_ref  1303 , can transition from a first voltage level, Vcpl_ref_lcm  1305 , to a second voltage level, Vcpl_ref_touch  1307 , and an LDO reference voltage, Vgl_ref  1309 , can transition from a first voltage level, Vgl_ref_lcm  1311 , to a second voltage level, Vgl_ref_touch  1313 . A charge pump enable signal, CP_CLK_EN  1315 , can be HIGH, which can cause the negative charge pump to draw current from Cvcpl  908 , in order to lower an output voltage level of the charge pump, VCPL  1317 , to a desired charge pump voltage level for the touch phase, VCPL_TOUCH, according to the new voltage level of charge pump reference voltage, Vcpl_ref_touch  1307 . As illustrated in  FIG. 13 , during a phase  1  an output voltage level of the LDO, VGL  1319 , can drop rapidly due to the charge transfer from Cvgl to Cvcpl via N-channel_FET (as described above, for example). Negative charge pump  902  can contribute little to the change in VGL level. At the end of phase  1 , an equilibrium point can be reached where VGL=VCPL and VGL&gt;VGL_TOUCH. During a phase  2 , both VCPL  1317  and VGL  1319  can be lowered. The transition between phase  2  and a phase  3  can occur when VCPL=VGL=VGL_TOUCH+Vdo, at which time negative LDO  902  can start regulating the VGL voltage level. In phase  3 , VGL  1319  voltage level can remain at VGL_TOUCH while negative charge pump  902  decreases VCPL  1317  voltage level until VCPL=VCPL_TOUCH=VGL_TOUCH+Vdo_touch. Depending on the overcharge level, Vdo_lcm, phase  1  may directly transition to phase  3 , that is, VGL  1319  can already be charged to VGL_TOUCH at the end of phase  1 . 
     Upon the falling edge of BSYNC signal  1301 , reference voltage Vcpl_ref  1303  into the charge pump can transition from Vcpl_ref_touch  1307  to Vcpl_ref_lcm  1305 , and reference voltage Vgl_ref  1309  into the negative LDO can transition from Vgl_ref_touch  1313  to Vgl_ref_lcm  1311 . Signal CP_CLK_EN  1315  can be HIGH, which can cause negative charge pump  902  to draw current from Cvcpl in order to lower the VCPL  1317  voltage level to VCPL_LCM, according to the new voltage level of negative charge pump reference voltage, Vcpl_ref_lcm  1305 . During a phase  4 , VGL  1319  voltage level can increase rapidly toward ground due to the charge transfer from ground to Cvgl via P-channel_FET in the negative LDO (as described above, for example). Because the display phase can be longer than the touch phase, for example, in some embodiments the display phase can be as much as three times longer than the touch phase, VCPL  1317  can be overcharged sufficiently during display phase to achieve fast settling during a settling time, Tsettle  1321 , during the transition from a display to a touch phase. 
     In some embodiments, VGH and VCPH may be adjusted in a similar way as described above, for example, in which VGH during touch mode can have a voltage level VGH_TOUCH, VGH during display mode can have a voltage level VGH_LCM, and VGH_TOUCH can be lower than VGH_LCM. In some embodiments, for example, a positive LDO can discharge a capacitance Cvgh through an N-channel FET to ground upon a rising edge of a BSYNC signal to lower the VGH voltage level, and a P-channel FET can transfer charge from a capacitance Cvcph to Cvgh upon a falling edge of the BSYNC signal as to increase the VGH voltage level. In some embodiments, VGH and VGL can be adjusted together as to maintain the same voltage differential (e.g., VGH_TOUCH-VGL_TOUCH˜VGH_LCM-VGL_LCM) in the touch phase and the display phase, as to operate within the voltage limits tolerable by other components of the system, such as a gate driver. It should also be understood, that different combinations of voltage levels for VCPH, VGH, etc., are possible and that all voltage levels can be programmable, as needed by a given application. In some embodiments, in which VGH and VGL can be adjusted together, that is, VGL and VGH can be lowered during transition from display-to-touch-phase and where VGL and VGH can be increased during transition from touch-to-display phase, charge from Cvcph and Cvgh can be recycled to Cvcpl and Cvgl upon transition from display phase to touch phase, and charge from Cvcpl and Cvgl can be recycled to Cvcph and Cvgh during the transition from touch phase to display phase, which can, for example, yield power savings. 
       FIG. 10  is a flowchart of an example operation of a touch screen device, such as touch screen device  900 , according to various embodiments of the disclosure. Reference to touch screen device  900  is made to illustrate one example implementation of the example operation of  FIG. 10 . During a display phase, an image can be updated ( 1001 ) on a touch screen of the device. A rising edge of a BSYNC signal can be detected ( 1002 ), and a touch sensing phase can be performed in response, for example, during a blanking period of the touch screen after the updating of the display. In the touch sensing phase, all gate lines can be set ( 1003 ) LOW to disable the display TFTs. Setting the gate lines LOW, essentially can pull the gate lines to the negative gate drive supply voltage VGL, which can be, for example, an output voltage of a negative LDO as described above. The charge pumps can be enabled ( 1004 ). VGL and VGH voltage levels can be lowered ( 1005 ) from VGL_LCM and VGH_LCM to VGL_TOUCH and VGH_TOUCH, for example, by using the example charge transfer mechanism described above. After the charge pumps are disabled, the sense amplifier feedback switch can be applied and released ( 1006 ) a certain time later to speed up settling prior to the first touch scan. The touch sensing scan can be performed ( 1007 ) for a time, TSCAN. After the touch sensing scan, the charge pumps can be enabled ( 1008 ) for a time, TGAP, to restore the VGL and VGH voltage levels to the desired levels VGL_TOUCH and VGH_TOUCH. If all touch scans are completed ( 1009 ) and after a falling edge of the BSYNC signal is detected ( 1010 ), the charge pumps can be enabled ( 1011 ), and VGL and VGH voltage levels can be raised from VGL_TOUCH and VGH_TOUCH to VGL_LCM and VGH_LCM, for example, by using the example charge transfer mechanism described above in preparation for the next display update. At  1009 , if all touch scans are not completed, the process can again disable ( 1005 ) the charge pumps and apply and release ( 1006 ) the sense amplifier feedback switch for quick settling in preparation for the next touch sensing scan. 
       FIG. 11  illustrates more details of an example touch sensing phase operation of touch screen device  900  according to various embodiments of the disclosure.  FIG. 11  shows a portion of a touch sensing phase of touch screen device  900  including periods of active touch sensing, during which a touch scan control  1101  of a touch controller (not shown) can perform touch scan steps to actively scan the touch screen. During a scan gap in between active touch sensing, a charge pump enable control signal  1103  of the touch controller can enable negative charge pump  902  for a portion of the scan gap. While negative charge pump  902  is enabled, a charge pump clock signal  1105  can clock the negative charge pump multiple times corresponding to multiple applications of VGL  905  to gate line  915 . Charge pump enable control signal  1103  can disable negative charge pump  902 , and feedback bypass controller  913  can send a feedback bypass control signal  1107  to close feedback bypass switch  911  to short the feedback loop of sense amplifier  906 . Feedback bypass control signal  1107  can open feedback bypass switch  911  prior to the next touch scan step, during which sense amplifier  906  can receive and amplify sense signals for further processing to determine touch. 
     Although embodiments of this disclosure have been fully described with reference to the accompanying drawings, it is to be noted that various changes and modifications including, but not limited to, combining features of different embodiments, omitting a feature or features, etc., as will be apparent to those skilled in the art in light of the present description and figures. For example, while the foregoing may describe example embodiments that can include multiple elements that can be used to reduce or eliminate effects of noise in touch sensing, such as an LDO, which can further include a capacitor (e.g., gate line capacitor  925 ), a voltage boost system, and a post-noise stabilizer system (e.g., feedback bypass switch  911  and feedback bypass controller  913 ), and corresponding methods of operation (e.g., various processes described in reference to  FIG. 10 ), it should be noted that each of these elements can be used independently of the others. In other words, some embodiments can include only one of these elements and/or processes, while other embodiments can include various combinations of two or more of these elements and/or processes, as one skilled in the art would readily understand in light of the disclosure. 
     It should be understood that one or more of the functions of performing touch sensing, controlling gate line voltages, etc., described above can be performed by computer-executable instructions, such as software/firmware, residing in a medium, such as a memory, that can be executed by a processor, as one skilled in the art would understand. The software/firmware can be stored and/or transported within any computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. In the context of this document, a “non-transitory computer-readable storage medium” can be any physical medium that can contain or store the program for use by or in connection with the instruction execution system, apparatus, or device. The non-transitory computer-readable storage medium can include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus or device, a portable computer diskette (magnetic), a random access memory (RAM) (magnetic), a read-only memory (ROM) (magnetic), an erasable programmable read-only memory (EPROM) (magnetic), a portable optical disc such a CD, CD-R, CD-RW, DVD, DVD-R, or DVD-RW, or flash memory such as compact flash cards, secured digital cards, USB memory devices, memory sticks, and the like. In the context of this document, a “non-transitory computer-readable storage medium” does not include signals. In contrast, in the context of this document, a “computer-readable medium” can include all of the media described above, and can also include signals. 
     Although various embodiments are described with respect to display pixels, one skilled in the art would understand that the term display pixels can be used interchangeably with the term display sub-pixels in embodiments in which display pixels are divided into sub-pixels. For example, some embodiments directed to RGB displays can include display pixels divided into red, green, and blue sub-pixels. One skilled in the art would understand that other types of display screen could be used. For example, in some embodiments, a sub-pixel may be based on other colors of light or other wavelengths of electromagnetic radiation (e.g., infrared) or may be based on a monochromatic configuration, in which each structure shown in the figures as a sub-pixel can be a pixel of a single color.

Metadata:
Filing Date: 20110923
Publication Date: 20170912
Grant Date: 20170912
Priority Date: 20110923
Inventors: KRAH CHRISTOPH HORST
WHITE KEVIN J.
BI YAFEI
Assignee: APPLE INC
CPC Classifications: [{"code": "G06F3/044", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0412", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/0418", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/04184", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0446", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/04164", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0443", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0412", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/04184", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0446", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0443", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/04164", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0443", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/04164", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/04184", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0412", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/0412", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/0446", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 46832621