PATENT DOCUMENT

Publication Number: US-9268445-B2
Application Number: US-201313921155-A
Country: US
Kind Code: B2

Title: Touch sensor panels with reduced static capacitance

Abstract:
Capacitive touch panels may include a plurality of positive voltage lines that are driven at a first phase. These positive voltage lines may be used to provide the drive capacitance signal sensed by one or more sense regions. The touch panels may also include a plurality of negative phase voltage lines that are driven at a phase that is different than the first phase. Both the positive and negative voltage lines may cross-under one or more sense regions. The negative phase voltage lines are able to counter act and reduce the static capacitance in the sense regions.

Claims:
What is claimed is: 
     
       1. A touch sensitive panel comprising:
 a plurality of pixels; 
 a plurality of first voltage lines that are driven at a first phase; 
 a plurality of second voltage lines that are driven at a second phase that is different than the first phase; 
 a plurality of drive regions comprising some of the plurality of pixels arranged in a matrix, each drive region coupled at least to one of the plurality of first voltage lines; and 
 at least one sense region comprising others of the plurality of pixels, arranged in a matrix and disposed between at least a first and a second drive regions of the plurality of drive regions, the plurality of first voltage lines and the plurality of second voltage lines crossing the at least one sense region and electrically isolated therefrom; and 
 wherein the second phase is opposite the first phase and wherein the first phase of the plurality of first voltage lines and the second phase of the plurality of second voltage lines reduce static capacitance in the at least one sense region as compared to a configuration in which the second voltage lines are not utilized. 
 
     
     
       2. The touch sensitive panel of  claim 1 , wherein the touch sensitive panel comprises an integrated touch screen and display. 
     
     
       3. The touch sensitive panel of  claim 1 , further comprising a plurality of sense regions, each sense region disposed between two of the plurality of drive regions. 
     
     
       4. The touch sensitive panel of  claim 1 , wherein touch regions are formed by capacitive coupling between at least one of the first and second drive regions and the at least one sense regions and the touch sensitive panel is configured for having a touch phase and a display phase. 
     
     
       5. The touch sensitive panel of  claim 1 , wherein the plurality of second voltage lines cross-under the first and second drive regions. 
     
     
       6. The touch sensitive panel of  claim 1 , wherein the number of second voltage lines that cross-under the first and second drive regions is less than the number of second voltage lines that cross-under the at least one sense region. 
     
     
       7. The touch sensitive panel of  claim 1 , wherein the plurality of drive region and the at least one sense region comprise a plurality of capacitive elements of the plurality of pixels. 
     
     
       8. The touch sensitive panel of  claim 7 , wherein:
 all of the capacitive elements of pixels in the first drive region are electrically connected together; 
 all of the capacitive elements of pixels in the second drive region are electrically connected together; and 
 all of the capacitive elements of pixels in the at least one sense region are electrically connected together. 
 
     
     
       9. The touch sensitive panel of  claim 7 , comprising a conductive member that electrically connects together all the pixels in a region. 
     
     
       10. The touch sensitive panel of  claim 9 , where the capacitive elements of pixels within each of the first and second drive regions are electrically connected together within their respective region by a plurality of first common voltage lines disposed along a first direction and a plurality of second common voltage lines disposed along a second, different direction. 
     
     
       11. The touch sensitive panel of  claim 10 , wherein the capacitive elements of pixels within the at least one sense region are electrically connected together by a plurality of third common voltage lines. 
     
     
       12. The touch sensitive panel of  claim 10 , wherein the plurality of first and second common voltage lines within each of the first and second drive regions are coupled to a drive plate disposed within each of the first and second drive regions. 
     
     
       13. A method of reducing static capacitance in a touch panel comprising:
 providing a plurality of pixels; 
 driving a plurality of first voltage lines at a first phase; 
 driving a plurality of second voltage lines at a second phase that is different than the first phase, wherein the first voltage lines and the second voltage lines cross-under a sense region; 
 coupling at least one of the plurality of first voltage lines to a plurality of drive regions comprising some of the plurality of pixels arranged in a matrix; and 
 disposing at least one sense region, comprising others of the plurality of pixels, arranged in a matrix, between at least a first and a second drive regions of the plurality of drive regions, the plurality of first voltage lines and the plurality of second voltage lines crossing the at least one sense region and electrically isolated therefrom; and 
 wherein the second phase is opposite the first phase and wherein the first phase of the plurality of the first voltage lines and the second phase of the plurality of second voltage lines reduce static capacitance in the at least one sense region as compared to a configuration in which the second voltage lines are not utilized. 
 
     
     
       14. The method of  claim 13 , further comprising forming touch regions by capacitive coupling between at least one of the first and second drive regions and the at least one sense regions. 
     
     
       15. The method of  claim 14 , wherein the second voltage lines cross-under the first and second drive regions. 
     
     
       16. The method of  claim 14 , wherein the number of second voltage lines that cross-under the first and second drive regions is less than the number of second voltage lines that cross-under the at least one sense region. 
     
     
       17. The method of  claim 14 , wherein the plurality of drive region and the at least one sense region comprise a plurality of capacitive elements of the plurality of pixels. 
     
     
       18. The method of  claim 13 , wherein the touch sensitive panel comprises an integrated touch screen and display. 
     
     
       19. The method of  claim 13 , further comprising forming a plurality of sense regions, each sense region disposed between two of the plurality of drive regions. 
     
     
       20. The method of  claim 13 , wherein the touch sensitive panel has a touch phase and a display phase. 
     
     
       21. The method of  claim 13 , further comprising:
 coupling together all of the capacitive elements of pixels in the first drive region; 
 coupling together all of the capacitive elements of pixels in the second drive region; and 
 coupling together all of the capacitive elements of pixels in the at least one sense region. 
 
     
     
       22. The touch sensitive panel of  claim 21 , comprising a conductive member that electrically connects all the pixels in a region. 
     
     
       23. A method of making a touch panel comprising:
 providing a plurality of pixels; 
 providing a plurality of first voltage lines that are driven at a first phase; 
 providing a first and second drive region, each comprising a plurality of capacitive elements of pixels arranged in a matrix and connected to the first voltage lines; 
 providing a sense region comprising a plurality of capacitive elements of pixels arranged in a matrix; 
 disposing the sense region between the first and second drive regions; 
 disposing the plurality of first voltage lines such that they cross-under the sense region and are electrically isolated therefrom; 
 selecting a number of second voltage lines to be driven at a second phase that is different than the first phase; 
 providing the selected number of second voltage lines that cross-under the sense region and are electrically isolated therefrom; and 
 wherein the second phase is the first phase and wherein the first phase of the plurality of first voltage lines and the second phase of the plurality of second voltage lines reduce static capacitance in the at least one sense region as compared to a configuration in which the second voltage lines are not utilized. 
 
     
     
       24. A touch screen including display pixels with capacitive elements, the touch screen comprising:
 a plurality of pixels; 
 a plurality of first voltage lines that are driven at a first phase; 
 a plurality of second voltage lines that are driven at a second phase that is different than the first phase; 
 a drive region comprising a plurality of capacitive elements of pixels connected to the first voltage lines; 
 a sense region, wherein the first voltage lines and the second voltage lines cross-under the sense region; and 
 wherein the second phase is opposite the first phase and wherein the first phase of the plurality of the first voltage lines and the second phase of the plurality of second voltage lines reduce static capacitance in the sense region as compared to a configuration in which the second voltage lines are not utilized. 
 
     
     
       25. A digital media player comprising a touch screen comprising:
 a plurality of pixels each have capacitive elements; 
 a plurality of first voltage lines that are driven at a first phase; 
 a plurality of second voltage lines that are driven at a second phase that is different than the first phase;
 a plurality of drive regions each comprising a some of the plurality of capacitive elements of pixels arranged in a matrix and connected to the first voltage lines; 
 
 a sense region comprising others of the plurality of capacitive elements of pixels arranged in a matrix and disposed between two of the plurality of drive regions, wherein the first voltage lines and the second voltage lines cross-under the sense region; and
 wherein the second phase is opposite the first phase and wherein the first phase of the plurality of first voltage lines and the second phase of the plurality of second voltage lines reduce static capacitance in the sense region as compared to a configuration in which the second voltage lies are not utilized. 
 
 
     
     
       26. A mobile telephone comprising a touch screen comprising:
 a plurality of pixels each have capacitive elements; 
 a plurality of first voltage lines that are driven at a first phase; 
 a plurality of second voltage lines that are driven at a second phase that is different than the first phase; 
 a plurality of drive regions each comprising a some of the plurality of capacitive elements of pixels arranged in a matrix and connected to the first voltage lines; 
 a sense region comprising others of the plurality of capacitive elements of pixels arranged in a matrix and disposed between two of the plurality of drive regions, wherein the first voltage lines and the second voltage lines cross-under the sense region; and 
 wherein the second phase is opposite the first phase and wherein the first phase of the plurality of first voltage lines and the second phase of the plurality of second voltage lines reduce static capacitance in the sense region as compared to a configuration in which the second voltage lines are not utilized. 
 
     
     
       27. A personal computer comprising a touch screen comprising:
 a plurality of pixels each have capacitive elements; 
 a plurality of first voltage lines that are driven at a first phase; 
 a plurality of second voltage lines that are driven at a second phase that is different than the first phase; 
 a plurality of drive regions each comprising a some of the plurality of capacitive elements of pixels arranged in a matrix and connected to the first voltage lines; 
 a sense region comprising others of the plurality of capacitive elements of pixels arranged in a matrix and disposed between two of the plurality of drive regions, wherein the first voltage lines and the second voltage lines cross-under the sense region; and 
 wherein the second phase is opposite the first phase and wherein the first phase of the plurality of first voltage lines and the second phase of the plurality of second voltage lines reduce static capacitance in the sense region as compared to a configuration in which the second voltage lines are not utilized.

Description:
FIELD OF THE INVENTION 
     This relates to touch sensor panels with reduced static capacitance, and more particularly to touch sensors that include negative phase voltage lines that reduce the static capacitance of the sensor panels. 
     BACKGROUND OF THE INVENTION 
     Many types of input devices are 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 generally allow a user to perform various functions by touching (e.g. physical contact or near-field proximity) 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 event and the position of the touch event on the touch sensor panel, and the computing system can then interpret the touch event in accordance with the display appearing at the time of the touch event, and thereafter can perform one or more actions based on the touch event. 
     Mutual capacitance 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). The lines are often arranged orthogonally 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. However, overlaying a display with a touch sensor panel can have drawbacks, such as added weight and thickness, and decreased brightness of the display. 
     SUMMARY OF THE INVENTION 
     This generally relates to touch sensor panels with reduced static capacitance, and more particularly to touch sensors that may include positive voltage drive lines that are used to drive the drive regions of the sensor panels and negative phase voltage lines that reduce the static capacitance of the sensor panels. By reducing the static capacitance the accuracy of the panels may be improved and the amount of power used to achieve an accurate touch may be reduced. 
     The touch panels may include a plurality of positive voltage lines that are driven at a first phase. These positive voltage lines may be used to provide the drive capacitance signal sensed by one or more sense regions. The touch panels may also include a plurality of negative phase voltage lines that are driven at a second phase that may be different than the first phase. Both the positive and negative voltage lines may cross-under one or more sense regions. The negative phase voltage lines are able to counter act and reduce the static capacitance in the sense region. The amount of static capacitance may be tuned by selecting the number of negative voltage lines that cross-under the sense regions. 
     One embodiment of a sensor panel that may include a matrix of voltage lines that may be driven in both a positive and negative phase manner may be a sensor panels with integrated LCD functionality. Such a sensor panel may include a matrix of voltage data lines for addressing the LCD and sense pixels individually. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a partial circuit diagram of an example LCD including a plurality of LCD pixels according to embodiments of the present invention. 
         FIG. 2  illustrates an exemplary LCD having display and touch modes in which touch regions can be formed by groups of pixels in the LCD according to embodiments of the invention. 
         FIG. 3  illustrates partial circuit diagrams of a pixel of a drive region and a pixel of a sense region according to embodiments of the invention. 
         FIG. 4A  illustrates example signals applied to the pixels of a drive region during an LCD phase and during a touch phase according to embodiments of the invention. 
         FIG. 4B  illustrates example signals applied to the pixels of a sense region during an LCD phase and during a touch phase according to embodiments of the invention. 
         FIG. 5A  illustrates details of an example operation of a storage capacitor of a drive region during a touch phase according to embodiments of the invention. 
         FIG. 5B  illustrates details of an example operation of a storage capacitor of a sense region during a touch phase according to embodiments of the invention. 
         FIG. 6  illustrates the components of a capacitance signal Csig measured at a sense region according to embodiments of the invention. 
         FIG. 7  illustrates an exemplary touch and display array including drive regions and sense regions according to embodiments of the invention. 
         FIG. 8  illustrates an exemplary touch and display array with reduced static capacitance in which “dummy” negative xVcom lines are used in connection with main xVcom lines according to embodiments of the invention. 
         FIG. 9A  illustrates an exemplary touch and display array with reduced static capacitance in which the number of “dummy” negative xVcom lines in the drive region are reduced according to embodiments of the invention. 
         FIG. 9B  illustrates the negative xVcom lines and the yVcom lines that are connected to the xVcom lines in  FIG. 9A  according to embodiments of the invention. 
         FIG. 9C  illustrates the positive xVcom lines and the yVcom lines that are connected to the positive xVcom lines in  FIG. 9A  according to embodiments of the invention. 
         FIG. 9D  illustrates the xVcom lines and the yVcom lines that are connected to ground in  FIG. 9A  according to embodiments of the invention. 
         FIG. 9E  illustrates the yVcom lines that are connected to the sense plate in  FIG. 9A  according to embodiments of the invention. 
         FIG. 10  illustrates a cross sectional view of a sense region and a cross sectional view of a drive region of an LCD and sensor panel according to embodiments of the invention. 
         FIG. 11  illustrates an exemplary computing system having an LCD with display and touch modes according to embodiments of the invention. 
         FIG. 12   a  illustrates an exemplary mobile telephone having an LCD with display and touch modes according to embodiments of the invention. 
         FIG. 12   b  illustrates an exemplary digital media player having an LCD with display and touch modes according to embodiments of the invention. 
         FIG. 12   c  illustrates an exemplary personal computer having an LCD with display and touch modes according to embodiments of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the following description of preferred 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 the invention 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 invention. 
     The description includes examples of touch panels with dual-function capacitive elements that can form (a) part of a display system that generates an image on the display, and (b) part of a touch sensing system that senses touch events on or near the display. The capacitive elements can be, for example, capacitors in pixels of an LCD that are configured to operate individually, each as a pixel storage capacitor, or electrode, of a pixel in the display system, and may be configured to operate collectively as elements of the touch sensing system. In this way, for example, a display with integrated touch sensing capability may be manufactured using fewer parts, layers and/or processing steps, and the display itself may be thinner and brighter. 
     Sensor panels with integrated LCD functionality may include a matrix of voltage data lines for addressing the LCD and sense pixels individually. Although touch panels that include the examples include these dual functioning elements, the concepts described herein also include sensor panel embodiments including voltage lines that do not include display functionalities. During a sense operation, some of the voltage lines may be driven in a positive phase to drive the drive regions of the sensor panel. In addition, one or more of the voltage lines may be driven in a negative phase with respect to the positive voltage lines used to drive the drive regions of the sensor panel. These negative phase voltage lines may be used to reduce the static capacitance of the sensor panels. 
       FIG. 1  is a partial circuit diagram of example LCD panel  100  including a plurality of LCD sub-pixels according to embodiments of the present invention. The sub-pixels of panel  100  are configured such that they are capable of dual-functionality as both LCD sub-pixels and touch sensor elements. That is, the sub-pixels include capacitive elements or electrodes that can operate as part of the LCD circuitry of the pixels and that can also operate as elements of touch sensing circuitry. In this way, panel  100  can operate as an LCD with integrated touch sensing capability.  FIG. 1  shows details of sub-pixels  101 ,  102 ,  103 , and  104  of panel  100 . Note that each of the sub-pixels can represent either red (R), green (G) or blue (B), with the combination of all three R, G and B sub-pixels forming a single color pixel. 
     Sub-pixel  102  can include thin film transistor (TFT)  155  with gate  155   a , source  155   b , and drain  155   c . Sub-pixel  102  can also include storage capacitor, Cst  157 , with upper electrode  157   a  and lower electrode  157   b , liquid crystal capacitor, Clc  159 , with sub-pixel electrode  159   a  and common electrode  159   b , and color filter voltage source, Vcf  161 . If a sub-pixel may be an in-plane-switching (IPS) device, Vcf can be, for example, a fringe field electrode connected to a common voltage line in parallel with Cst  157 . If a sub-pixel does not utilize IPS, Vcf  161  can be, for example, an ITO layer on the color filter glass. Sub-pixel  102  can also include portion  117   a  of a data line for green (G) color data, Gdata line  117 , and portion  113   b  of gate line  113 . Gate  155   a  may be connected to gate line portion  113   b , and source  155   b  may be connected to Gdata line portion  117   a . Upper electrode  157   a  of Cst  157  may be connected to drain  155   c  of TFT  155 , and lower electrode  157   b  of Cst  157  may be connected to portion  121   b  of a common voltage line that runs in the x-direction, xVcom  121 . Sub-pixel electrode  159   a  of Clc  159  may be connected to drain  155   c  of TFT  155 , and common electrode  159   b  of Clc  159  may be connected to Vcf  161 . 
     The circuit diagram of sub-pixel  103  can be identical to that of sub-pixel  102 . However, as shown in  FIG. 1 , color data line  119  running through sub-pixel  103  carries blue (B) color data. Sub-pixels  102  and  103  can be, for example, known LCD sub-pixels. 
     Similar to sub-pixels  102  and  103 , sub-pixel  101  may include thin film transistor (TFT)  105  with gate  105   a , source  105   b , and drain  105   c . Sub-pixel  101  may also includes storage capacitor Cst  107 , with an upper electrode  107   a  and lower electrode  107   b , liquid crystal capacitor Clc  109 , with sub-pixel electrode  109   a  and common electrode  109   b , and color filter voltage source, Vcf  111 . Sub-pixel  101  may also include portion  115   a  of a data line for red (R) color data, Rdata line  115 , and portion  113   a  of gate line  113 . Gate  105   a  may be connected to gate line portion  113   a , and source  105   b  may be connected to Rdata line portion  115   a . Upper electrode  107   a  of Cst  107  may be connected to drain  105   c  of TFT  105 , and lower electrode  107   b  of Cst  107  may be connected to portion  121   a  of xVcom  121 . Sub-pixel electrode  109   a  of Clc  109  may be connected to drain  105   c  of TFT  105 , and common electrode  109   b  of Clc  109  may be connected to Vcf  111 . 
     Unlike sub-pixels  102  and  103 , sub-pixel  101  may also includes portion  123   a  of a common voltage line running in the y-direction, yVcom  123 . In addition, sub-pixel  101  may include connection  127  that connects portion  121   a  to portion  123   a . Thus, connection  127  may connect xVcom  121  and yVcom  123 . 
     Sub-pixel  104  (only partially shown in  FIG. 1 ) may be similar to sub-pixel  101 , except that portion  125   a  of yVcom  125  may have break (open)  131 , and portion  121   b  of xVcom  121  may have break  133 . 
     As can be seen in  FIG. 1 , the lower electrodes of storage capacitors of sub-pixels  101 ,  102 , and  103  may be connected together by xVcom  121 . This connection may be used in conjunction with gate lines, data lines, and transistors, to allow sub-pixels to be addressed. The addition of vertical common voltage lines along with connections to the horizontal common voltage lines allows grouping of sub-pixels in both the x-direction and y-direction, as described in further detail below. For example, yVcom  123  and connection  127  to xVcom  121  can allow the storage capacitors of sub-pixels  101 ,  102 , and  103  to be connected to storage capacitors of sub-pixels that may be above and below sub-pixels  101 ,  102 ,  103  (the sub-pixels above and below are not shown). For example, the sub-pixels immediately above sub-pixels  101 ,  102 , and  103  can have the same configurations as sub-pixels  101 ,  102 , and  103 , respectively. In this case, the storage capacitors of the sub-pixels immediately above sub-pixels  101 ,  102 , and  103  would be connected to the storage capacitors of sub-pixels  101 ,  102 , and  103 . 
     In general, an LCD panel could be configured such that the storage capacitors of all sub-pixels in the panel may be connected together, for example, through at least one vertical common voltage line with connections to a plurality of horizontal common voltage lines. Another LCD panel could be configured such that different groups of sub-pixels may be connected together to form a plurality of separate regions of connected-together storage capacitors. 
     One way to create separate regions may be by forming breaks (opens) in the horizontal and/or vertical common lines. For example, yVcom  125  of panel  100  may have break  131 , which can allow sub-pixels above the break to be isolated from sub-pixels below the break. Likewise, xVcom  121  may have break  133 , which can allow sub-pixels to the right of the break to be isolated from sub-pixels to the left of the break. 
       FIG. 2  illustrates an exemplary LCD and touch panel having display and touch modes in which touch regions can be formed by groups of pixels in the LCD according to embodiments of the invention. In the example of  FIG. 2 , LCD  200  can have a plurality of touch regions, which can include a plurality of drive regions  210  and a plurality of sense regions  220 . The drive regions  210  and the sense regions  220  can include groups of pixels  203 , which can display data in the display mode and sense touch in the touch mode. For simplicity, each pixel  203  is shown as a single block with a vertical common voltage line yVcom  202  and a horizontal common voltage line xVcom  201 , where each single pixel block can represent a group of red, green, and blue sub-pixels each having a data line, as shown in  FIG. 1 . 
     The drive region may be responsible for creating the field sensed by the sense region for touch sensing. Drive region  210  can be formed by connecting at least one vertical common voltage line yVcom  202  of pixel  203  with at least one horizontal common voltage line xVcom  201  of the pixel at connection  204 , thereby forming a drive region consisting of a row of pixels. For example, drive region  210  is formed by connecting the xVcom line  201  for each of three rows to the yVcom line  202 . A conductive transparent drive plate (e.g. indium tin oxide (ITO) plate) can be used to cover the drive region and connect to the vertical and horizontal common voltage lines. Generally, a drive region may be larger than a single pixel, and may be comparable to the size of a finger tip, for example, in order to effectively receive a touch or near touch on the LCD. 
     For example, a drive region can be formed by connecting a plurality of vertical common voltage lines yVcom with a plurality of horizontal common voltage lines xVcom, thereby forming a drive region consisting of a matrix of pixels. In some embodiments, drive regions proximate to each other can share horizontal common voltage lines xVcom, which can be used to stimulate the drive regions with stimulation signals, which will be described in more detail later. In some embodiments, drive regions proximate to each other can share vertical common voltage lines yVcom with breaks  212  in the lines between the drive regions in order to minimize the lines causing parasitic capacitance that could interfere with the received touch or near touch. The ground regions  214  formed of xVcom lines  201  and yVcom lines  202  between the drive regions may be connected to ground or a virtual ground in order to further minimize the interference between drive regions  210  and between the drive regions and the sense regions  220 . Optionally and alternatively, the vertical common voltage line breaks can be omitted and the lines shared in their entirety among the drive regions. 
     A sense region  220  can be formed by at least one vertical common voltage line yVcom  202  of a pixel, thereby forming a sense region consisting of a column of pixels. A conductive transparent sense plate (e.g., ITO plate) can be used to cover the sense region and connect to the vertical common voltage line. Generally, a sense region may be larger than a single column of pixels in order to effectively sense a received touch or near touch on the touch sensitive device. For example, a sense region can be formed by a plurality of vertical common voltage lines yVcom, thereby forming a sense region consisting of a matrix of pixels. In the sense region, the vertical common voltage lines yVcom can be unconnected from and can cross over (at  211 ) the horizontal common voltage lines xVcom to form the mutual capacitance structure for touch sensing. This cross over yVcom and xVcom also forms an additional parasitic capacitance between the sense and drive ITO regions. 
     In operation during touch mode, the horizontal common voltage lines xVcom  201  can transmit stimulation signals to stimulate the drive regions  210  to form electric field lines between the stimulated drive regions and adjacent sense regions  220 . When an object such as a finger touches or near touches a stimulated drive region  210 , the object can block some of the electric field lines extending to the adjacent sense regions  220 , thereby reducing the amount of charge coupled to these adjacent sense regions. This reduction in charge can be sensed by the sense regions  220  as an “image” of touch. This touch image can be transmitted along the vertical common voltage lines yVcom  202  to touch circuitry for further processing. 
     The drive regions of  FIG. 2  are shown as rows of connected drive ITO rectangles regions and the sense regions of  FIG. 2  are shown as rectangles extending the vertical length of the LCD. 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 invention. It is to be understood that the pixels used to form the touch regions are not limited to those described above, but can be any suitable pixels having touch capabilities according to embodiments of the invention. 
     A touch sensing operation according to embodiments of the invention will be described with reference to  FIGS. 3-5B . For the sake of clarity, the operation is described in terms of a single drive pixel and a single sense pixel. However, it is understood that the drive pixel may be connected to other drive pixels in a drive region and the sense pixel may be connected to other sense pixels in the sense region, as described above. Thus, in actual operation, the entire drive region may be driven, and the entire sense region can contribute to the sensing of touch. 
       FIG. 3  shows partial circuit diagrams of pixel  301  of an example drive region and pixel  303  of an example sense region. Pixels  301  and  303  include TFTs  307  and  309 , gate lines  311  and  312 , data lines  313  and  314 , xVcom lines  315  and yVcom lines  316 , fringe field electrodes  319  and  321 , and storage capacitors  323  and  325 . In the example of  FIG. 3 , storage capacitors  323  and  325  each have a capacitance of about 300 fF (femto-Farads). A lower electrode of fringe field electrode  321  of pixel  303  can be connected, through yVcom  316 , to charge amplifier  326  in the sense circuitry. Charge amplifier  326  holds this line at a virtual ground such that any charge that gets injected from fringe field electrode  321  shows up as a voltage output of the amplifier. While the feedback element of the amplifier is shown as a capacitor, it may also function as a resistor or a combination of a resistor and capacitor. The feedback can also be, for example, a resistor and capacitor feedback for minimizing die-size of the touch sensing circuitry. Exemplary  FIG. 3  also shows finger  327  that creates a stray capacitance of approximately 3 fF with a cover glass (not shown), and shows other stray capacitances in the pixels, each of which is approximately 3 fF. 
       FIG. 4A  shows example signals applied through xVcom  315  to the pixels of the drive region, including pixel  301 , during an example LCD phase and during an example touch phase. During the LCD phase, xVcom  315  and yVcom  316  may, for example, be driven with a square wave signal of 2.5V+/−2.5V, in order to perform LCD inversion. The LCD phase may, for example, be 12 ms in duration. In the touch phase, xVcom  315  may, for example, be driven with 15 to 20 consecutive stimulation phases lasting 200 microseconds each while yVcom  316  may be maintained at a virtual ground of sense preamp of touch ASIC . The stimulation signals in this case may be square or sinusoidal signals of 2.5V+/−2V each having the same frequency and a relative phase of either 0 degrees or 180 degrees (corresponding to “+” and “−” in  FIG. 4A ). The touch phase may, for example, be 4 ms in duration. 
       FIG. 5A  shows details of the operation of storage capacitor  323  during the touch phase. In particular, because the capacitance of storage capacitor  323  may be much higher than the other capacitances (i.e., stray capacitances shown in  FIG. 3 ), almost all (approximately 90%) of the AC component of the 2.5V+/−2V sinusoidal stimulation signal that may be applied at the lower electrode of the storage capacitor may be transferred to the upper electrode. In this manner the, Liquid Crystal of LCD will experience minimal electric field changes due to the touch stimuli and maintain its charge state as it was set by during the LCD mode. Therefore, the upper electrode, along with bottom Vcom electrode of  319  may be charged to 4.5 volts DC for the touch mode operation of the LCD, sees a sinusoidal signal of 4.5V+/−1.9V. These signals may be passed to the corresponding top and bottom in comb structures of electrodes  321  which may be kept at the virtual ground of the sense preamp of touch ASIC. Thus, fringe field and Vcom electrodes of  319  and  321  together with the interference of the user finger  327  can form a mutual capacitance touch sensing structure. 
     At the same time, fringe field electrode  319  may be configured to operate as a drive element for the touch sensing system, the fringe field electrode may continue to operate as a part of the LCD system. As shown in  FIG. 5A , while the voltages of the comb structures of fringe field electrode may be each modulated at approximately +/−2V, the relative voltage between the comb structures remains approximately constant at 2V+/−0.1V. This relative voltage may be the voltage that is seen by the liquid crystal of the pixel for the LCD operation. The 0.1V AC variance in the relative voltage during the touch phase should have an acceptably low affect on the LCD, particularly since the AC variance would typically have a frequency that may be higher than the response time for the liquid crystal. For example, the stimulation signal frequency, and hence the frequency of the AC variance, would typically be more than 100 kHz. However, the response time for liquid crystal is typically less than 100 Hz. Therefore, the fringe field electrode&#39;s function as a drive element in the touch system should not interfere with the fringe field electrode&#39;s LCD function. 
     Referring now to  FIGS. 3 ,  4 B, and  5 B, an example operation of the sense region will now be described.  FIG. 4B  shows signals applied through yVcom  316  to the pixels of the sense region, including pixel  303 , during the LCD and touch phases described above. As with the drive region, yVcom  316  may be driven with a square wave signal of 2.5V+/−2.5V in order to perform LCD inversion during the LCD phase. During the touch phase, yVcom  316  may be connected to amplifier  326 , which holds the voltage at or near a virtual ground of 2.5V. Consequently, fringe field electrode  321  may also be held at 2.5V. As shown in  FIG. 3 , fringing electrical fields propagate from fringe field electrode  319  to fringe field electrode  321 . As described above, the fringing electric fields may be modulated at approximately +/−2V by the drive region. When these fields are received by the top electrode of fringing field electrode  321 , most of the signal gets transferred to the lower electrode, because pixel  303  may have the same or similar stray capacitances and storage capacitance as pixel  301 . 
     Because yVcom  316  may be connected to charge amplifier  326 , and may be held at virtual ground, any charge that gets injected will show up as an output voltage of the charge amplifier. This output voltage provides the touch sense information for the touch sensing system. For example, when finger  327  gets close to the fringing fields, it captures some fields and grounds them, which causes a disturbance in the fields. This disturbance can be detected by the touch system as a disturbance in the output voltage of charge amplifier  326 .  FIG. 5B  shows that approximately 90% of a received fringing field at pixel  302  that impinges onto the electrode half of the capacitor which may also be connected to the drain of the TFT  325  will be transferred to charge amplifier  326 . 100% of the charge that impinges onto the electrode half of the capacitor, which is connected directly to yVcom  316 , will be transferred to charge amplifier  326 . The ratio of charge impinging onto each electrode will depend on the LCD design. For non-IPS, nearly 100% of the finger affected charge will impinge on the Vcom electrode because the patterned CF plate is nearest the finger. For an IPS-type display the ratio will be closer to half and half because each part of the electrode may have approximately equal area (or ¼ vs. ¾) facing the finger. For some sub-types of IPS displays, the fringing electrodes may not be coplanar, and the majority of the upward facing area may be devoted to the Vcom electrode. 
     The example driving and sensing operations of  FIGS. 3 ,  4 A-B, and  5 A-B are described using single pixels for the sake of clarity. 
       FIG. 6  shows the components of the capacitance signal Vsense  600  measured at a sense region. As discussed above, the fringe field lines that extend from the drive regions to the sense regions create a capacitance signal that may be sensed at a sense region. Vsense  600  represents the total capacitance signal measured at a sense region. Vsense  600  includes noise  602 , which represents capacitance due to coupling between the sense region and various background components. Csig.nom  604  is the starting coupling between the drive and sense region. When a finger or other object blocks a portion of the fringing electrical fields that extend from the drive and sense regions, Csig.nom  604  and Vsense  600  may be reduced by ΔCsig  606 . Accordingly, the signal capacitance at the sense region becomes Csig.nom-ΔCsig, where Csig.nom represents the static (no touch) component and ΔCsig represents the dynamic (touch) component. 
     Noise  602  may always be nonzero due to the inability of a finger, palm or other object to block all electric fields that may be produced on a touch panel, especially those electric fields that remain entirely within the touch panel. In addition, it should be understood that as a finger is pushed harder or more completely onto the multi-touch panel, the finger can tend to flatten, blocking more and more of the electric fields, and thus ΔCsig can be variable and representative of how completely the finger is pushing down on the panel (i.e. a range from “no-touch” to “full-touch”). 
     The resolution of ΔCsig as measured at the sense region may be related to the proportional dynamic range ΔCsig/Vsense. The proportionate dynamic range can be increased by increasing the Csig.nom relative to the noise component. This can be accomplished by increasing the power supplied to the drive lines. This, however, also increases the power consumption of the device. Another method of increasing the proportionate dynamic range ΔCsig/Csig may include removing components of Vsense that do not contribute to ΔCsig. 
       FIG. 7  illustrates an embodiment of touch and display array  700  including drive regions  702  and sense regions  704 . The drive regions  702  may be formed from one or more drive pixels  710 . The drive pixels include a connection to at least one vertical common voltage line yVcom  706  and at least one horizontal common voltage line xVcom  708 . Drive ITO plate  712  can be used to cover drive region  702  and provide for connection of the vertical and horizontal common voltage lines  706  and  708  in drive region  702 . 
     A sense region  704  can be formed by at least one vertical common voltage line yVcom  706  of sense pixel  714 , thereby forming sense region  704  including column of pixels  714 . Sense ITO plate  716  can be used to cover the sense region and provide connection to vertical common voltage line  706 . 
     In operation during touch mode, the horizontal common voltage lines xVcom  708  can transmit stimulation signals to stimulate the drive regions  702  to form electric field lines between the stimulated drive regions and adjacent sense regions  704 . These electric field lines contribute to Csig.nom. When an electrically conductive object, such as a finger, touches or near touches a stimulated drive region  702 , the object can block some of the electric field lines extending to the adjacent sense regions  704 , thereby reducing the amount of charge coupled to these adjacent drive/sense regions. This reduction in charge is ΔCsig. The xVcom lines may not be connected to the yVcom lines or to the sense ITO plate  716  in sense regions  704 . However, the xVcom lines which are used to drive the drive regions nonetheless cross-under the sense region. As used herein in, the term cross-under means that the lines are in the same plain as the relevant region, but are conductively insulated from the region. The difference in potential between these cross-under xVcom lines and sense ITO plates  716  produces a cross-under capacitance that contributes to Csig.nom. 
       FIG. 8  illustrates an embodiment in which “dummy” negative xVcom lines  800  are used in connection with main xVcom lines  802 . The negative xVcom may be driven with a negative phase with respect to the main drive signal. The negative phase may be completely opposite the main xVcom phase or any different phase than the main drive signal. The negative xVcom lines are connected to neither yVcom lines  706  nor to the drive ITO plate  712 . Accordingly, only the main xVcom lines  802  are connected to the drive ITO plate  712  and are used to drive the drive regions  702 . 
     Both the main xVcom lines  802  and the negative xVcom lines  800  cross-under and are conductively insulated from the yVcom lines in the sense regions  704 . The cross-under capacitance of the negative phase xVcom lines  800  relative to the sense pixels in the sense region  704  counteracts the cross-under capacitance of the positive phase main xVcom lines  802 . 
     In addition, by selecting an imbalance of more negative phase than positive phase, the inherent static Csig.nom due to the touch pixels electrodes that does not contribute to ΔCsig may be subtracted out. (This inherent static Csig.nom may, for example, be due to the fringe fields that remain within the touch panel, for example, fringe fields through a LCD polarizer, cover glass, even the out of plane above the cover glass etc.) A benefit of subtracting this Csig.nom out at the pixel location, instead of later, is that the compensated signal is in the same physical location, and subject to identical propagation delays as it travels down the sense column yVcom lines to the receive chip. 
     An imbalance of more negative phase cross-under capacitance may be created by using more cross-under negative xVcom lines than main positive xVcom lines. In addition, or alternatively, the voltage on the negative xVcom lines may be increased relative to the voltage of the positive xVcom lines. In  FIG. 8 , an imbalance of more negative xVcom lines  800  relative to the positive xVcom lines  802  is shown. The negative xVcom lines  800  have the same voltage, but opposite phase as the positive xVcom lines  802 . 
     Since the negative xVcom lines are not connected to the drive ITO plate and are not used to drive the drive regions, it may be preferred to minimize the area occupied by the negative xVcom lines in the drive area. Accordingly,  FIGS. 9A-9E  illustrate an embodiment in which the number of negative xVcom lines  904  in the drive regions may be reduced. The negative xVcom lines may then be split to create an imbalance of negative xVcom lines in the sense drive regions. Portions of the yVcom lines in the drive region may be used to split the negative xVcom lines. In  FIG. 9A , the majority of the drive region  908  includes four negative xVcom  904  lines that are not connected to the ITO drive plate  910  and nine positive xVcom lines  906  that are connected to the ITO drive plate  910  and may be used to drive the drive region  908 . In the vicinity in which the negative xVcom lines encroach the sense region  912 , they are split using the yVcom lines  914 . In the sense region  912 , the four negative xVcom lines may be split to form eight negative xVcom lines that cross-under the sense region  912 . Further, the number of positive phase xVcom lines that cross-under the sense region  912  may be similarly reduced. Although in this example the negative xVcom lines that cross-under the sense region are doubled, the actual number of negative xVcom lines that crossunder the sense region  912  can be chosen to tune the coupling capacitance of the anti-phase negative xVcom lines in the cross-under region. By reducing the total static Csig in this region, the amount of power required to drive the drive lines may be reduced. 
     The number of negative xVcom lines in the drive region may be chosen to keep the resistance of the lines low enough to not adversely affect the phase of the negative xVcom lines. 
       FIG. 9B  illustrates the negative xVcom lines  904  and the yVcom lines  920  that may be connected to the xVcom lines. These lines are not connected to and cross-under the drive ITO plates  910  and the sense ITO plates  916 .  FIG. 9C  illustrates the positive xVcom lines  906  and the yVcom lines  922  that may be connected to the positive xVcom lines  906 . These xVcom lines  906  may be connected to drive ITO plates  910 . The xVcom lines  906  are not connected to and cross-under sense ITO plates  916 .  FIG. 9D  illustrates the xVcom lines  922  and the yVcom lines  924  that may be connected to ground. The ground may be an actual ground or a virtual ground. The ground regions may be used to isolate the different regions and reduce the parasitic capacitance formed between the different regions in the touch panel. The ground regions are not connected to either the drive ITO plates  910  or the sense ITO plates  916 .  FIG. 9E  illustrates the yVcom lines  926  that may be connected to sense plate  916 . Since xVcom lines  928  are not connected to drive source, these lines may also be connected to yVcom lines  926  and sense plate  916 . 
       FIG. 10  illustrates a cross sectional view of a sense region and a cross sectional view of a drive region of an LCD and sensor panel according to embodiments of the invention. In sense section  1000 , the sense ITO plate  1004  may be connected to the yVcom line  1008  using via  1006 . The xVcom line may not be electrically connected to the sense ITO plate  1010 . In drive section  1002 , the drive ITO plate  1012  may be electrically connected both to yVcom line  1014  and xVcom line  1016 . 
       FIG. 11  illustrates an exemplary computing system that can include one or more of the embodiments of the invention described herein. In the example of  FIG. 11 , computing system  1100  can include one or more panel processors  1102  and peripherals  1104 , and panel subsystem  1106 . Peripherals  1104  can include, but are not limited to, random access memory (RAM) or other types of memory or storage, watchdog timers and the like. Panel subsystem  1106  can include, but is not limited to, one or more sense channels  1108 , channel scan logic (analog or digital)  1110  and driver logic (analog or digital)  1114 . Channel scan logic  1110  can access RAM  1112 , autonomously read data from sense channels  1108  and provide control signals  1017  for the sense channels. In addition, channel scan logic  1110  can control driver logic  1114  to generate stimulation signals  1116  at various phases that can be simultaneously applied to drive lines of touch screen  1124 . Panel subsystem  1106  can operate at a low digital logic voltage level (e.g. 1.7 to 3.3V). Driver logic  1114  can generate a supply voltage greater that the digital logic level supply voltages by cascading two charge storage devices, e.g., capacitors, together to form charge pump  1015 . Charge pump  1015  can be used to generate stimulation signals  1116  that can have amplitudes of about twice the digital logic level supply voltages (e.g. 3.4 to 6.6V). Although  FIG. 11  shows charge pump  1015  separate from driver logic  1114 , the charge pump can be part of the driver logic. In some embodiments, panel subsystem  1106 , panel processor  1102  and peripherals  1104  can be integrated into a single application specific integrated circuit (ASIC). 
     Touch screen  1124  can include a capacitive sensing medium having a plurality of drive regions  1127  and a plurality of sense regions  1129  according to embodiments of the invention. The sense and drive regions may include a plurality of xVcom voltage lines  1134  and a plurality of yVcom voltage lines  1136 . One or more of the xVcom lines may be run in a negative phase with respect to one or more of the other xVcom lines voltage lines to reduce the static capacitance of the sensor panel. Each drive region  1027  and each sense region  1029  can comprise a plurality of capacitive elements, which can be viewed as pixels  1126  and which can be particularly useful when touch screen  1124  is viewed as capturing an “image” of touch. (In other words, after panel subsystem  1106  has determined whether a touch event has been detected at each touch sensor in the touch screen, the pattern of touch sensors in the multi-touch screen at which a touch event occurred can be viewed as an “image” of touch (e.g. a pattern of fingers touching the screen).) The presence of a finger or other object near or on the touch screen can be detected by measuring changes to a signal charge present at the pixels being touched, which is a function of signal capacitance. Each sense region of touch screen  1124  can drive sense channel  1108  in panel subsystem  1106 . 
     Computing system  1100  can also include host processor  1128  for receiving outputs from panel processor  1102  and performing actions based on the outputs that can include, but are not limited to, moving one or more objects 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 coupled 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  1128  can also perform additional functions that may not be related to panel processing, and can be coupled to program storage  1132  and touch screen  1124  such as an LCD for providing a user interface to a user of the device. 
     Note that one or more of the functions described above can be performed by firmware stored in memory (e.g. one of the peripherals  1104  in  FIG. 11 ) and executed by panel processor  1102 , or stored in program storage  1132  and executed by host processor  1128 . The firmware can also 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 “computer-readable medium” can be any medium that can contain or store the program for use by or in connection with the instruction execution system, apparatus, or device. The computer readable 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. 
     The firmware can also be propagated within any transport 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 “transport medium” can be any medium that can communicate, propagate or transport the program for use by or in connection with the instruction execution system, apparatus, or device. The transport readable medium can include, but is not limited to, an electronic, magnetic, optical, electromagnetic or infrared wired or wireless propagation medium. 
     It is to be understood that the touch screen may not be limited to touch, as described in  FIG. 11 , but may be a proximity screen or any other screen switchable between a display mode and a touch mode according to embodiments of the invention. In addition, the touch sensor panel described herein can be either a single-touch or a multi-touch sensor panel. 
       FIG. 12   a  illustrates an exemplary mobile telephone  1236  that can include touch screen  1224  and other computing system blocks that can be utilized for configuring data lines of the touch screen during a touch mode of the telephone. 
       FIG. 12   b  illustrates an exemplary digital media player  1140  that can include touch screen  1224  and other computing system blocks that can be utilized for configuring data lines of the touch screen during a touch mode of the media player. 
       FIG. 12   c  illustrates an exemplary personal computer  1244  that can include touch screen  1224 , touch sensor panel (trackpad)  1226 , and other computing system blocks that can be utilized for configuring data lines of the touch screen during a touch mode of the personal computer. 
     The mobile telephone, media player, and personal computer of  FIGS. 12   a ,  12   b  and  12   c  can be thinner, lighter, more efficient, and cost and power saving with an LCD having display and touch modes with configurable data lines according to embodiments of the invention. 
     Although embodiments of this invention have been fully described with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art. Such changes and modifications are to be understood as being included within the scope of embodiments of this invention as defined by the appended claims.

Metadata:
Filing Date: 20130618
Publication Date: 20160223
Grant Date: 20160223
Priority Date: 20090202
Inventors: HOTELLING STEVEN PORTER
YOUSEFPOR MARDUKE
Assignee: APPLE INC
CPC Classifications: [{"code": "G06F2203/04112", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/0416", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03K17/9622", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0412", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/044", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/0445", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0446", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/04166", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0443", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/04184", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/04164", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0412", "inventive": true, "first": true, "tree": "[]"}, {"code": "H03K17/9622", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03K17/9622", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/044", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F2203/04112", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/04164", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F2203/04112", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F2203/04112", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/0412", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0412", "inventive": true, "first": true, "tree": "[]"}, {"code": "H03K17/9622", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/047", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 42396404