PATENT DOCUMENT

Publication Number: US-10965285-B2
Application Number: US-201916706757-A
Country: US
Kind Code: B2

Title: Multiple controllers for a capacitive sensing device

Abstract:
A capacitive sensing device can include multiple capacitive sensors. A first device controller is operatively connected to a portion of the capacitive sensors, while a second device controller is operatively connected to another portion of capacitive sensors. A common node or shield can be connected between the first device controller and the second device controller. Charging and discharging events of selected drive lines in the capacitive sensing device and/or of the common node or shield can be synchronized to reduce undesirable effects such as noise and/or to prevent the charging events and the discharging events from overlapping with each other. One or more reference capacitive sensors can be shared by the multiple device controllers.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 a set of capacitive sensors; 
 an array of pixels associated with the set of capacitive sensors that are operable to perform display functions; 
 a first controller that controls a first group of the set of capacitive sensors; and 
 a second controller that controls a second group of the set of capacitive sensors. 
 
     
     
       2. The electronic device of  claim 1 , wherein the first controller is inoperative to control charging of at least one of the second group of the set of capacitive sensors. 
     
     
       3. The electronic device of  claim 2 , wherein the second controller is inoperative to control charging of at least one of the first group of the set of capacitive sensors. 
     
     
       4. The electronic device of  claim 2 , wherein the second controller is inoperative to control discharging of at least one of the first group of the set of capacitive sensors. 
     
     
       5. The electronic device of  claim 1 , wherein the first controller is inoperative to control discharging of at least one of the second group of the set of capacitive sensors. 
     
     
       6. The electronic device of  claim 5 , wherein the second controller is inoperative to control charging of at least one of the first group of the set of capacitive sensors. 
     
     
       7. The electronic device of  claim 5 , wherein the second controller is inoperative to control discharging of at least one of the first group of the set of capacitive sensors. 
     
     
       8. The electronic device of  claim 1 , wherein at least one of the set of capacitive sensors is unassociated with the array of pixels. 
     
     
       9. An electronic device, comprising:
 a display including pixels that combine display functions and capacitive sensing functions; 
 a first controller that controls the capacitive sensing functions of a first group of the pixels; and 
 a second controller that controls the capacitive sensing functions of a second group of the pixels. 
 
     
     
       10. The electronic device of  claim 9 , wherein the first controller controls capacitive sensing charging functions of the first group of the pixels. 
     
     
       11. The electronic device of  claim 10 , wherein the second controller is inoperative to control the capacitive sensing charging functions of the first group of the pixels. 
     
     
       12. The electronic device of  claim 9 , wherein the first controller controls capacitive sensing discharging functions of the first group of the pixels. 
     
     
       13. The electronic device of  claim 12 , wherein the second controller is inoperative to control the capacitive sensing discharging functions of the first group of the pixels. 
     
     
       14. The electronic device of  claim 9 , wherein a touch to a surface associated with the display is determinable using at least a capacitance change detected using the capacitive sensing functions of the pixels. 
     
     
       15. The electronic device of  claim 9 , wherein an amount of a force applied to a surface associated with the display is determinable using at least a capacitance change detected using the capacitive sensing functions of the pixels. 
     
     
       16. An electronic device, comprising:
 a touch surface; 
 a display, coupled to the touch surface, including a set of pixels that is operable to perform display functions; 
 a set of capacitive sensors; 
 a first controller that controls a first group of the set of capacitive sensors; and 
 a second controller that controls a second group of the set of capacitive sensors; 
 wherein, each capacitive sensor in the set of capacitive sensors is associated with a pixel in the set of pixels. 
 
     
     
       17. The electronic device of  claim 16 , wherein the first controller and the second controller both control a third group of the set of capacitive sensors. 
     
     
       18. The electronic device of  claim 16 , wherein the first controller controls all of the set of capacitive sensors. 
     
     
       19. The electronic device of  claim 16 , wherein at least one of the set of pixels is unassociated with the set of capacitive sensors. 
     
     
       20. The electronic device of  claim 16 , wherein:
 the first controller controls charging and discharging of at least one the first group of the set of capacitive sensors; and 
 the second controller is inoperative to control charging and discharging of the at least one of the first group of the set of capacitive sensors.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 15/493,481, filed Apr. 21, 2017, which is a continuation of U.S. patent application Ser. No. 14/196,710, filed Mar. 4, 2014, now U.S. Pat. No. 9,660,646, which is a nonprovisional of, and claims the benefit under 35 U.S.C. § 119(e) of, U.S. Provisional Application No. 61/775,649 filed on Mar. 10, 2013, the contents of which are incorporated herein by reference in their entirety. 
    
    
     FIELD 
     The present invention relates generally to display screens, and more specifically to touch or force sensing through capacitive sensing elements. 
     BACKGROUND 
     Touch sensitive devices have become increasingly popular in electronic devices due to their ease of use, their versatility of operation, and their ability to be integrated into an electronic device. Computer monitors, laptop and notebook computers, smart telephones, tablet computers, and portable media players are equipped with touch sensitive devices that are configured to sense touch as a user input. The touch may be sensed in accordance with one of several different touch sensing techniques, including, but not limited to, capacitive touch sensing. 
     In some instances, a touch sensing device can detect touch with a capacitive sensing device. A capacitive sensing device can be small, for example, when included in a track pad. In a touchscreen, the capacitive sensing device can be larger. Typically, a device controller or integrated circuit is connected to a capacitive sensing device to control the operations of the capacitive sensing device. Users expect a larger touch sensitive device to be as sensitive to touch as a smaller touch sensitive device. However, it can be challenging to control a large capacitive sensing device with one device controller. This can be due, in part, to the finite number of connections the device controller has to connect to the various signal lines used to control or operate the capacitive sensors of the touch sensitive device. For example, in some embodiments, each capacitive sensor in a capacitive sensing device can be formed at the intersection of a drive line and a separate sense line. The drive and sense lines are connected to the device controller, thus requiring multiple connections. Further, a shield in the capacitive sensing device may need to have a signal repeatedly applied to it during scanning operations. The signal applied to the shield can be produced by the device controller. Likewise, other components in the capacitive sensing elements may require control signals to operate, and these control signals may be generated by the device controller. 
     SUMMARY 
     In one aspect, one device controller can be operatively connected to a portion of the capacitive sensors in a capacitive sensing device, and another device controller can be operatively connected to another portion of the capacitive sensors in the capacitive sensing device. The capacitive sensors can be disposed, for example, in individual pixels or with intersecting drive and signal lines. The device controllers can each include a switching device, and the switching devices can be operatively connected to a common node or a shield. Charging and discharging of the drive lines and sense lines in the capacitive sensing device can be controlled by the first device controller and the second device controller. Charging and discharging of the common node or shield can be controlled by the device controllers through the switching devices. In some embodiments, the charging and discharging of a common node or shield can be synchronized to reduce or eliminate undesirable effects, such as cross-coupling noise. By way of example only, signals having three phases, an on phase, a tri-state phase, and an off phase can be applied to the common node or shield to prevent the charging events and the discharging events from overlapping with each other. 
     In another aspect, the switching devices can each include a first switch and a second switch connected to a switch node. A first current supply can be connected between a power supply and the first switch. A second current supply may be connected between the second switch and a reference signal level. In some embodiments, the reference signal level is ground. The common node can be operatively connected to the switch node in one switching device and to the switch node is the other switching device. 
     In another aspect, one or more reference capacitive sensors can be operatively connected to the first and second device controllers and shared by the first and second device controllers. At least one of the shared reference capacitive sensors can provide a reference capacitance that can be compared to the measured capacitances to determine if any changes in capacitance have occurred. The shared reference capacitive sensor or sensors can be disposed within the capacitive sensors in the capacitive sensing device and/or outside of the capacitive sensors. 
     In another aspect, a surface of a touch device can be partitioned into two or more sections with at least one section being scanned for capacitive changes in the capacitive sensors included in the at least one section. By way of example only, a touchscreen can be logically partitioned into two or more sections, and one section can be used to display an image while one or more additional sections can be used to interact with the image. The section or sections that are used to interact with the image can use an applied force to interact with the image. The capacitive sensors in the section or sections that is used to interact with the image can be operatively connected to one device controller. If so, the one device controller can be used to control a scanning operation. However, some of the capacitive sensors in the section or sections can be operatively connected to a first device controller and other capacitive sensors in the section or sections can be operatively connected to a second device controller. If so, both the first and second device controllers can be used to control the scanning operation. The charging and discharging of a common node or shield during the scanning operation can be synchronized to reduce or eliminate any undesirable effects. 
     And in yet another aspect, an electronic device can include a capacitive sensing device, a first device controller operatively connected to a portion of the capacitive sensors in the capacitive sensing device, and a second device controller operatively connected to another portion of the capacitive sensors in the capacitive sensing device. Both the first and second device controllers can each include a switching device. Each switching device may include a first switch and a second switch connected to a switch node. A first current supply can be connected between a power supply and the first switch. A second current supply may be connected between the second switch and a reference signal level. In some embodiments, the reference signal level is ground. The common node can be operatively connected to the switch node in one switching device and to the switch node is the other switching device. The electronic device may be an output device such as a display, or an input device such as a track pad or home button. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments are better understood with reference to the following drawings. The elements of the drawings are not necessarily to scale relative to each other. Identical reference numerals have been used, where possible, to designate identical features that are common to the figures. 
         FIGS. 1A-1C  depict front perspective views of examples of electronic devices that include capacitive sensing systems; 
         FIG. 2  illustrates a conceptual drawing of a capacitive sensing device; 
         FIGS. 3A-3B  depict conceptual drawings of an array of pixels that include capacitive sensors; 
         FIG. 4  illustrates a simplified block diagram of one example of a capacitive sensing system; 
         FIG. 5  depicts a simplified schematic view of one example of the switching devices  432 ,  434  shown in  FIG. 4 ; 
         FIG. 6  illustrates one example of a timing diagram for the switching devices  432 ,  434  shown in  FIG. 4 ; 
         FIG. 7  depicts a simplified conceptual drawing of a shared capacitive sensor in a capacitive sensing system; 
         FIG. 8  illustrates one example of a layout for a capacitive sensing device having a shared capacitive sensor; 
         FIG. 9  depicts another layout for a capacitive sensing device having a shared capacitive sensor and multiple device controllers; and 
         FIG. 10  is a flowchart of one embodiment of a method for operating a multiple device controller capacitive sensing system. 
     
    
    
     DETAILED DESCRIPTION 
     In some embodiments described herein, a capacitive sensing system includes a capacitive sensing device and multiple device controllers. The multiple device controllers can allow the capacitive sensing system to have scalability. For example, when the capacitive sensing device is smaller, one device controller can be used to control and operate the capacitive sensing device. Alternatively, when the capacitive sensing device is larger, multiple device controllers can be used to control and operate the capacitive sensing device. For example, in one embodiment, one device controller can drive the drive and sense lines for all of the capacitive sensors in a smaller capacitive sensing device while multiple device controllers can drive the drive and sense lines in a larger capacitive sensing device. 
     The surface of a touch device can be logically partitioned into two or more sections, and the capacitive sensors in at least one section can be used to detect an applied force. For example, a touchscreen can be used to display a visual image, such as, for example, a user interface, a program, or a settings screen. In one embodiment, the screen can be logically divided into one or more sections and one or more sections can be used to detect a force applied to the screen while other sections of the screen can be used for visual display only (i.e., not used for force detection). A number of folders can be displayed on the screen, for example, and an applied force can be used to interact with only one of the folders. Another example can include a program, such as a video game, that uses one or more sections of the screen for controlling or interacting with the video game using one or more applied forces. 
     In one embodiment, when a common node in the capacitive sensing system is to be charged and discharged concurrently with the drive and sense lines during a scanning operation, one device controller can charge and discharge the common node in a smaller system while the multiple device controllers can each charge and discharge the common node in a larger system. When multiple device controllers are used to control a scanning operation, the charging and discharging cycles of both the drive lines and the common node can be synchronized to reduce noise caused in part by stray capacitances. By way of example only, an intermediate state can be included in the signals output from the multiple controllers to prevent the charging and discharging events from overlapping. 
     Typically, the measured capacitances are compared to a reference or absolute capacitance when determining whether a force has been applied to a touch device. When multiple device controllers are used to sense capacitance changes, the reference capacitive sensor can be shared by the multiple device controllers. The shared reference capacitive sensor can be a discrete capacitive sensor separate from the capacitive sensing device, or the shared reference capacitive sensor can be included in the capacitive sensing device. Additionally, more than one reference capacitive sensor can be used. 
     Directional terminology, such as “top”, “bottom”, “front”, “back”, “leading”, “trailing”, etc., is used with reference to the orientation of the Figure(s) being described. Because components of embodiments described herein can be positioned in a number of different orientations, the directional terminology is used for purposes of illustration only and is in no way limiting. 
     Referring now to  FIGS. 1A-1C , there are shown front perspective views of examples of electronic devices that can include capacitive sensing systems. As shown in  FIG. 1A , the electronic device  102  can be a laptop or netbook computer that includes a display  104  and a touch device, shown in the illustrated embodiment as a track pad  106 . An enclosure  108  can form an outer surface or partial outer surface and protective case for the internal components of the electronic device  102 , and may at least partially surround the display  104  and the track pad  106 . The enclosure  108  can be formed of one or more components operably connected together, such as a front piece and a back piece. 
     The display  104  is configured to display a visual output for the electronic device  102 . The display  104  can be implemented with any suitable display technology, including, but not limited to, a liquid crystal display (LCD), an organic light-emitting display (OLED), or organic electro-luminescence (OEL) display. The display  104  can include a multi-touch capacitive sensing touchscreen in some embodiments. The display  104  can include at least one capacitive sensing system that detects touch or force using capacitive changes at capacitive sensors. 
     The track pad  106  can be used to interact with one or more viewable objects on the display  104 . For example, the track pad  106  can be used to move a cursor or to select a file or program (represented by an icon) shown on the display. The track pad  106  can use capacitive sensing to detect an object, such as a finger or a conductive stylus, near or on the surface of the track pad  106 . The track pad  106  can include a capacitive sensing system that detects touch through capacitive changes at capacitive sensors. Additionally or alternatively, the same or another capacitive sensing system can be used to detect an amount of force applied to the track pad  106  using capacitive changes. 
       FIG. 1B  is a front perspective view of another electronic device that can include a capacitive sensing system. In the illustrated embodiment, the electronic device  110  is a smart telephone that includes an enclosure  112  surrounding a display  114  and one or more buttons  116  or input devices. The enclosure  112  can be similar to the enclosure described in conjunction with  FIG. 1A , but may vary in form factor and function. 
     The display  114  can be implemented with any suitable display, including, but not limited to, a multi-touch capacitive sensing touchscreen (i.e., a touch device) that uses liquid crystal display (LCD) technology, organic light-emitting display (OLED) technology, or organic electro luminescence (OEL) technology. A capacitive sensing touchscreen device can detect a touch or force using capacitive changes at capacitive sensors. 
     The button  116  can take the form of a home button, which may be a mechanical button, a soft button (e.g., a button that does not physically move but still accepts inputs), an icon or image on a display, and so on. Further, in some embodiments, the button  116  can be integrated as part of a cover glass of the electronic device. 
     Referring now to  FIG. 1C , there is shown a front perspective view of another electronic device that can include a capacitive sensing system. In the illustrated embodiment, the electronic device  118  is a tablet computer that can include a display  120 , an enclosure  122 , and one or more buttons  124  or input devices. The enclosure, display, and the one or more buttons can be similar to the enclosure, display, and button described in conjunction with  FIG. 1B , but may vary in form factor and function. 
     The electronic device  118  can also include one or more receiving ports  126 . A receiving port  126  can receive one or more plugs or connectors, including, but not limited to, a universal serial bus cable, a tip ring sleeve connector, or the like. 
       FIG. 2  illustrates a conceptual drawing of capacitive sensing device. The capacitive sensing device  200  can include a set of drive lines  202  arranged in columns and a set of sense lines  204  arranged in rows. In other embodiments, the sense lines can be arranged in columns and the drive lines in rows. It should be noted that the term “lines” is used herein to mean simply conductive pathways, as one skilled in the art will recognize the pathways are not limited to elements that are strictly linear, but can include pathways that change direction and can include pathways of different sizes, shapes, and materials. 
     The drive lines  202  can be charged by drive signals output from one or more drive circuits (not shown) and received by one or more drive interfaces  206  in the capacitive sensing device  200 . By way of example only, the drive circuit(s) or the drive interface(s)  206  can included a timed circuit that selects each drive line  202  in turn and drives that line for a relatively short period of time, eventually selecting each drive line  202  in a round-robin fashion. 
     Similarly, sense signals received on the sense lines  204  can be output by one or more sense interfaces  208  in the capacitive sensing device  200  and transmitted to one or more sense circuits (not shown). By way of example only, the sense circuit(s) or the sense interface(s)  208  can included a timed circuit that selects each sense line  204  in turn and senses that row for a relatively short period of time, eventually selecting each sense line  204  in a round-robin fashion. 
     The drive lines  202  and the sense lines  204  are configured to produce individual capacitive sensors  210 . The individual capacitive sensors  210  can be dispersed such that each capacitive sensor  210  can represents a different position on the touch device. 
     In another embodiment, each capacitive sensor is included in an individual pixel of a display layer, thereby combining the display and capacitive sensing functions in each pixel.  FIGS. 3A-3B  depict conceptual drawings of an array of pixels that include capacitive sensors. In the illustrated embodiment, the individual pixels are included on a display layer  300  and each pixel combines the display and capacitive sensing functions. For simplicity, only the capacitive sensing function is described herein. 
     A conductive layer  308  is patterned into discrete electrodes  302  with each electrode connected to a sense line  304 . Each discrete electrode  302  is included in a pixel. The sense lines  304  can be connected to sense circuits (not shown) through a sense interface  306 . The conductive layer  308  with the discrete electrodes  302  can be disposed over a common node layer  310 . The combination of an individual electrode  302  and the common node layer  310  forms a capacitive sensor. In another embodiment, the conductive layer  308  can be disposed under the common node layer  310 . Typically, an insulating layer is disposed between the conductive layer  308  and the common node layer  310 . 
     The common node layer  310  can be driven with an excitation signal when the capacitive sensors in the array of pixels operate in a mutual capacitance mode. The sense lines  304  are scanned to measure the capacitance between the electrodes  302  in each pixel and the common node layer  310 . 
     The common node layer  310  can be connected to a reference voltage or signal, such as ground, when the capacitive sensors in the array of pixels operate in a self-capacitance mode. In a self-capacitance system, the capacitance of a single electrode with respect to ground can be measured. A sense line  304  can be used to measure the capacitance between an electrode  302  and the common node layer  310  (e.g., ground). 
     Additionally or alternatively, embodiments can include force sensing systems that detect an amount of force applied to a touch device, or changes in amounts of force applied to the touch device, by measuring capacitive changes at one or more capacitive sensors. The touch device can be a touchscreen, a track pad, or other input device. A force detecting system can include a flexible touchable surface that is included in a device or display stack. The device or display stack can further include a compressible gap and a capacitive sensing device capable of detecting changes in capacitance in response to surface flex, such as flex caused by an applied force. The compressible gap can include an air gap, a compressible substance, or a compressible structure. 
     By way of example only, two patterned conductive layers can both be active layers and operate in a mutual capacitance force-sensing mode. As the device or display stack is pushed or otherwise moved downward, the capacitance of individual pixel capacitive sensors or row/column intersection may increase, since the layers are moved closer to one another. This increase in capacitance may be correlated to a decrease in distance between the layers, and thus, to an amount of force needed to move the layers a given distance. 
     Alternately, one patterned conductive layer can be active while the other conductive layer is passive, thereby operating in a self-capacitance force-sensing mode. As the active layer moves toward the self-capacitive sense layer, the capacitance measured at any individual pixel capacitive sensor or row/column intersection may change. Again, this change in capacitance may be correlated to a change in distance between the conductive layers and, thus, to an amount of force required to move the layers that distance. 
     Referring now to  FIG. 4 , there is shown a simplified block diagram of one example of a capacitive sensing system. The capacitive sensing system  400  includes a first device controller  402 , a capacitive sensing device  404 , and a second device controller  406 . The first and second device controllers  402 ,  406  can be implemented with any type of suitable controller, including, but not limited to, an application specific integrated circuit (ASIC). 
     In one embodiment, the first device controller  402  can be used to control a portion of the capacitive sensors in the capacitive sensing device  404  and the second device controller  406  can control another portion of the capacitive sensors. In another embodiment, only one device controller can be used to control the capacitive sensors in the capacitive sensing device  404 . The number of device controllers that is used to control the capacitive sensing device  404  can be based on a one or more system aspects, including, but not limited to, the number of capacitive sensors in the capacitive sensing device  404  and/or the configuration of the capacitive sensing device. Additionally, when multiple controllers are used to control a capacitive sensing device, the portions of the capacitive sensing device that each controller controls can be equal or can vary. By way of example only, each controller can control half of the capacitive sensors in a capacitive sensing device. 
     The first and second device controllers  402 ,  406  can each include a drive circuit  408 ,  410  that provides a drive signal on a respective signal line  412 ,  414 . As described earlier, the drive signal can be selectively applied to the drive lines (e.g.,  202  in  FIG. 2 ) in the capacitive sensing device  404 . The signal lines  412 ,  414  can be implemented as conductive traces or with other conductive routing technologies such as those associated with printed circuit boards, flexible circuits, and integrated circuits. 
     The first and second device controllers  402 ,  406  can each further include a sense circuit  416 ,  418  that receives sensed signals on a respective signal line  420 ,  422 . As described earlier, the sensed signals can be selectively transmitted from the sense lines (e.g.,  204  in  FIG. 2 ) to a sense circuit  416 ,  418 . The signal lines  420 ,  422  can be implemented as conductive traces or with other conductive routing technologies such as those associated with printed circuit boards, flexible circuits, and integrated circuits. 
     Scan logic  424 ,  426  can be connected to the sense circuits  416 ,  418  and can provide control for respective sense circuits  416 ,  418  to selectively scan the sense lines in the capacitive sensing device  404 . The scan logic  424 ,  426  can be connected to respective drive circuits  408 ,  410  and can control the drive circuits  408 ,  410  to generate drive signals at various frequencies and phases that can be selectively applied to the drive lines in the capacitive sensing device  404 . 
     Each device controller  402 ,  406  can further include a touch processor  428 ,  430 , such as, for example, a microprocessor. A touch processor  428 ,  430  can be connected to a respective scan logic  424 ,  426  and can control the scan logic  424 ,  426  and can process the sensed signals. The touch processor  428 ,  430  can be used to detect an amount of force applied to a touch device, or changes in amounts of force applied to the touch device in one embodiment. In another embodiment, a host processor (not shown) can be in communication with the touch processors  428 ,  430  and the host processor can be used to detect an amount of force, or changes in amounts of force, applied to the touch device. 
     The device controllers  402 ,  406  can each include a switching device  432 ,  434  that can be connected to a respective touch processor  428 ,  430  and to a common node  436 . The common node  436  can be made of any suitable conductive material or combination of conductive materials, including, but not limited to, a metal. By way of example only, the common node  436  can be a shield that is configured to protect the capacitive sensing device  404  and to reduce errors in capacitance measurements, which can be caused in part by stray or parasitic capacitances. 
     The touch processors  428 ,  430  can be used to control the switching devices  432 ,  434  to selectively apply a signal to the common node  436  and to selectively discharge the signal from the common node  436 . The switching devices  432 ,  434  will be discussed in more detail with respect to  FIG. 5 . 
     A power supply  438 ,  440  is connected to each device controller  402 ,  406 . The power supplies  438 ,  440  can be implemented as a single shared power supply or as two separate power supplies. The power supplies  438 ,  440  can be any suitable type of power supply, including, but not limited to a voltage source. 
       FIG. 5  illustrates a simplified schematic view of one example of the switching devices  432 ,  434  shown in  FIG. 4 . Switching devices  432 ,  434  can each include a first current source  500 ,  502  connected to a respective power supply  438 ,  440 . The first current sources  500 ,  502  can each be connected in series to a respective first switch  504 ,  506 . The first switches  504 ,  506  can each be connected in series to a respective second switch  508 ,  510 . And the second switches  508 ,  510  can each be connected in series to a respective second current source  512 ,  514 . The second current sources  512 ,  514  can each be connected to ground. In other embodiments, a voltage source connected to a switch having non-overlapping switch openings and closings, or a voltage source connected to a comparative switch, can be used in place of one or more current sources  500 ,  502 ,  512 ,  514 . 
     The common node  436  is connected between switch nodes  516 ,  518 . In one embodiment of a row and column self-capacitance sensing system, a scanning operation includes selecting a drive line (e.g.,  202  in  FIG. 2 ) using the scan logic and a respective drive circuit, and the drive line charged or driven to a given voltage or current level. To reduce stray capacitances, the common node  436  is driven to the given voltage or current level using the switching devices  432 ,  434 . The sense lines are then scanned and the capacitances are measured and compared to a reference capacitance to determine if any changes in capacitance have occurred. For example, a capacitance change can occur when a finger or conductive stylus applies one or more forces to the touch device. 
     The charge on the selected drive line and on the common node  436  is then discharged. The selected drive line and the common node can be discharged by connecting the selected drive line and the common node to a reference level, such as ground. The selected drive line is discharged using the scan logic and respective drive circuit while the common node  436  is discharged using the switching devices  432 ,  434 . The scanning process is repeated for each drive line. Thus, the capacitance of each capacitive sensor is measured by selectively charging each drive line and the common node, measuring the capacitance by sensing the sense lines, and then discharging the selected drive line and the common node  436 . 
     With the capacitance sensing system shown in  FIG. 4 , the device controllers  402 ,  406  can individually charge and discharge some of the capacitive sensors in the capacitive sensing device  404 , and can control the charging and discharging of the common node  436 . Each charging and discharging cycle of the signal lines  412 ,  414  and the common node  436  can be coordinated to reduce or eliminate cross-coupling noise that may be generated when the charging and/or discharging events occur out of phase. For example, if all of the drive lines and the common node are to be charged and discharged, the charging and discharging events can be synchronized so that the integration period for the capacitive sensors is opened and closed at the same, or substantially the same, time. Additionally or alternatively, the charging and discharging events can be synchronized so that the components and associated charge and discharge levels have time to settle in case the charging and/or discharging events occur at different speeds. 
     In an embodiment of a per-pixel self-capacitance sensing device, the common node (e.g.,  310  in  FIG. 3B ) is driven with an excitation or drive signal and the sense lines (e.g.,  304  in  FIG. 3A ) are scanned to measure the capacitance of each pixel capacitive sensor. When multiple controllers are used to control a scanning operation, the device controllers can control the charging and discharging of the common node  436  using the switching devices  432 ,  434 . 
     Referring now to  FIG. 6 , there is shown one example of a timing diagram for the switching devices  432 ,  434  shown in  FIG. 5 . The illustrated timing diagram can be used for a capacitive sensing device that operates in a mutual capacitance mode and includes the capacitive sensors in each pixel in a pixel array. Prior to time T 1 , both switching devices  432 ,  434  connect the common node  436  to a reference level  600 , such as ground. When a scanning operation is to begin, the current sources  500 ,  502  can be placed in an intermediate or tri-state phase  602  by placing the switches  504 ,  506 ,  508 ,  510  in an open state. An intermediate or tri-state phase is a phase where no active drive signal is output from the current sources. 
     At time T 2 , the current sources  500 ,  502  can be placed in an on phase to charge the common node  436  by closing the switches  504 ,  506  (switches  508 ,  510  remain open). When the charging event is complete at time T 3 , the current sources  500 ,  502  can be returned to the tri-state phase  602  by opening the switches  504 ,  506  (switches  508 ,  510  remain open). At time T 4 , the current sources  500 ,  502  can be placed in an off phase and the switches  508 ,  510  can be placed in a closed state (switches  504 ,  506  remain open). 
     The tri-state phases can prevent the on and off states of the current sources from overlapping. For example, the on and off states of the current sources can be a little out of phase with respect to each other. The tri-state phase provides additional time for the two current sources to be in the on or off states concurrently. 
     When a capacitive sensing system determines whether a force or forces has been applied to a touch device, the measured capacitances are typically compared to a reference or absolute capacitance to determine if a capacitance change has occurred at one or more capacitive sensors. The reference capacitance can be shared by the multiple device controllers in some embodiments.  FIG. 7  depicts a simplified conceptual drawing of a shared capacitive sensor in a capacitive sensing system. A capacitive sensing device  700  is connected to device controllers  702 ,  704 . Each device controller  702 ,  704  can control only a portion of the capacitive sensors in the capacitive sensing device  700  in one embodiment. 
     Reference capacitance sensor  706  can be measured by both device controllers  702 ,  704 . The reference capacitance sensor  706  can be a separate and discrete capacitive sensor, or the reference capacitance sensor  706  can be included in the capacitive sensing device  700 . Although only one reference capacitance sensor is shown, a capacitive sensing system can include one or more reference capacitance sensors. 
     Referring now to  FIG. 8 , there is shown one example of a layout for a capacitive sensing device having a shared capacitive sensor and multiple device controllers. The shared capacitive sensor  800  can be the capacitive sensor positioned in the center of the capacitive sensing device. Additionally, each device controller may control only a portion of the capacitive sensors in the capacitive sensing device. In the illustrated embodiment, one device controller may control the capacitive sensors free of hatch lines while the other device controller controls the capacitive sensors that include the hatch lines. Control of the capacitive sensing device is roughly divided in half in the illustrated embodiment, with one device controller controlling one half of the capacitive sensors and the other device controller controlling the other half of capacitive sensors. 
       FIG. 9  illustrates another layout for a capacitive sensing device having a shared capacitive sensor and multiple device controllers. The shared capacitive sensor  900  can be the capacitive sensor positioned in the center of the capacitive sensing device. In the illustrated embodiment, one device controller may control the capacitive sensors not including hatch lines while the other device controller controls the capacitive sensors that include the hatch lines. Control of the capacitive sensors in the capacitive sensing device is configured in a checkerboard pattern. In some embodiments, an artifact may be more easily diagnosed with this configuration. The artifact can be produced, for example, by a defect or break in the capacitive sensing system or in the electronic device. Alternatively, it may be easier to compensate for a discrepancy in one device controller compared to the other device controller because the artifact can be uniform across the capacitive sensing device instead of occurring at a seam in the capacitive sensing device where the control shifts from one device controller to the other. 
     Other embodiments can include any number of shared capacitive sensors. For example, an entire row of column of capacitive sensors can be shared. Alternatively, multiple shared capacitive sensors can be distributed throughout a capacitive sensing device. 
     Referring now to  FIG. 10 , there is shown a flowchart of one embodiment of a method for operating a multiple device controller capacitive sensing system. Initially, a determination is made at block  1000  as to whether a surface of a touch device is to be partitioned logically into two or more sections. For example, as described earlier, a number of folders can be displayed on a touchscreen and an applied force can be used to interact with only one of the folders. In another example, a program, such as a video game, can use one or more sections of the touchscreen for controlling or interacting with the video game through one or more applied forces. 
     If the surface of the touch device is to be partitioned, the method continues at block  1002  where the surface is partitioned into sections and the capacitive sensors included in at least one section that is to be used to detect an applied force are identified. A determination is then made at block  1004  as to whether one device controller is to be used to control the scanning operation. The number of device controllers that are used to control the scanning operation can be determined by which capacitive sensors are to be scanned during the scanning operation. The capacitive sensors in the at least one section to be scanned can be operatively connected to only one device controller (e.g. either the first device controller or the second device controller), or some of the capacitive sensors can be connected to the first device controller and the other capacitive sensors can be connected to the second device controller. So if all of the capacitive sensors in the at least one section to be scanned are connected to only the first device controller or to only the second device controller, then the respective device controller is used to control the scanning operation (block  1006 ). The charging and discharging events that occur during the scanning operation are controlled by the respective device controller. 
     However, if some of the capacitive sensors in the at least one section to be scanned are operatively connected to the first device controller and the other capacitive sensors to be scanned are operatively connected to the second device controller, then both the first and second device controllers are used to control the scanning operation (block  1008 ). The charging and discharging events that occur during the scanning operation can be controlled and synchronized by both the first and second device controllers. 
     Various embodiments have been described in detail with particular reference to certain features thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the disclosure. For example, embodiments can use more than two device controllers to control a capacitive sensing device. As another example, the embodiments described herein have described the two device controllers independently controlling a capacitive sensing device. The multiple device controllers are the same with respect to each other. Other embodiments are not limited to this construction. For example, the multiple device controllers can be configured in a master-slave arrangement. Differentiating logic would be included in such an arrangement that instructs one device controller to be the master and the other device controller to be a slave. In the master-slave arrangement, one device controller is different from the other device controller. 
     Additionally, the embodiments described herein have been described as detecting one or more applied forces on a touch device. Other embodiments can use multiple device controllers to detect one or more touches on the touch device. With touch detection, the capacitance of one or more capacitive sensors changes when a finger (or fingers) or a conductive stylus touch the touch device. 
     And even though specific embodiments have been described herein, it should be noted that the application is not limited to these embodiments. In particular, any features described with respect to one embodiment may also be used in other embodiments, where compatible. Likewise, the features of the different embodiments may be exchanged, where compatible.

Metadata:
Filing Date: 20191208
Publication Date: 20210330
Grant Date: 20210330
Priority Date: 20130310
Inventors: SAUER, Christian M.
RICHARDS, PETER W.
Assignee: APPLE INC
CPC Classifications: [{"code": "G06F3/041661", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0446", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03K17/9622", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/0446", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0445", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/03547", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/041661", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03K17/9622", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/0447", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0443", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F2203/04107", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/0412", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0412", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/041661", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/03547", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/0446", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F2203/04107", "inventive": false, "first": false, "tree": "[]"}, {"code": "H03K17/9622", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/0443", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 58708203