Abstract:
Disclosed herein is an electronic device including a first touch circuit to be coupled to a first touch sensing unit, the first touch sensing unit having first drive lines and first sense lines intersecting the first drive lines. A second touch circuit is to be coupled to a second touch sensing unit, the second touch sensing unit having second drive lines and second sense lines intersecting the second drive lines. A touch force circuit is to be coupled to a touch force sensing unit, the touch force sensing unit having third drive lines and third sense lines intersecting the third drive lines. The first touch circuit, second touch circuit, and touch force circuit are configured to drive the first, second, and third drive lines as a function of a synchronization signal, and acquire data from the first, second, and third sense lines as a function of the synchronization signal.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure generally relates to capacitive touch screen controller integrated circuits, and, more particularly, to a technique for using a touch screen controller integrated circuit to acquire touch data from different touch sensors in a correlated fashion. 
       BACKGROUND 
       [0002]    A touch screen display is a device that can detect an object in contact therewith or in proximity thereto. The touch screen display includes display layer covered with a touch-sensitive matrix that can detect a user&#39;s touch by way of a finger or stylus, for example. Touch screen displays are used in various applications such as mobile phones, tablets, and smartwatches. A touch screen display may enable various types of user input, such as touch selection of items or alphanumeric input via a displayed virtual keypad. Touch screen displays can measure various parameters of the user&#39;s touch, such as the location, duration, pressure, etc. 
         [0003]    One type of touch screen display is a capacitive touch screen. A capacitive touch screen may include a matrix of conductive rows and columns overlaid on the display layer forming mutual capacitance sensors. In mutual capacitance sensors, a mutual capacitance at the intersection of each row and column of the matrix may be sensed. A change in mutual capacitance between a row and a column may indicate that an object, such as a finger, is touching the screen or is in proximity to the screen near the region of intersection of the row and column. 
         [0004]    In some electronic devices, a capacitive touch screen may have multiple layers of mutual capacitance sensors in a stacked arrangement, with one layer being used to determine the X and Y coordinates of a touch location, and with another layer being used to determine the force or pressure with which the object making the touch presses against the capacitive touch screen. These different sensing layers may contain different numbers of mutual capacitance sensors. Due to the different number of mutual capacitance sensors, the pitch of these different sensing layers is not equal, which may adversely affect the accuracy of acquired touch data, in that data of a given touch event as acquired by the different sensing layers may not be cross correlated between those different sensing layers. 
         [0005]    Thus, a need exists within the art for techniques by which touch data collected from different mutual capacitance sensors can be cross correlated, at the time of acquisition. 
       SUMMARY 
       [0006]    This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter. 
         [0007]    Disclosed herein is an electronic device including a first touch circuit to be coupled to a first touch sensing unit, the first touch sensing unit having first drive lines and first sense lines intersecting the first drive lines. A second touch circuit is to be coupled to a second touch sensing unit, the second touch sensing unit having second drive lines and second sense lines intersecting the second drive lines. A touch force circuit is to be coupled to a touch force sensing unit, the touch force sensing unit having third drive lines and third sense lines intersecting the third drive lines. The first touch circuit, second touch circuit, and touch force circuit are configured to drive the first, second, and third drive lines as a function of a synchronization signal, and acquire data from the first, second, and third sense lines as a function of the synchronization signal. 
         [0008]    A method aspect disclosed herein includes generating a synchronization signal. In response to the synchronization signal, first, second, and third drive lines are driven, and data is acquired from first, second, and third sense lines intersecting the first, second, and third drive lines. The synchronization signal is not a system clock signal. 
         [0009]    Also disclosed herein is an electronic device including a first touch circuit to be coupled to a first touch sensing unit, and a second touch circuit to be coupled to a second touch sensing unit. One of the first touch circuit and the second touch integrated circuit is configured to generate a synchronization signal. The first and second touch circuits are configured to, in response to receipt of the synchronization signal, synchronously acquire touch data from the first and second touch sensing units, respectively. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1A  illustrates a portion of a capacitive touch matrix for touch location sensing. 
           [0011]      FIG. 1B  illustrates a mutual capacitance intersection in the matrix. 
           [0012]      FIG. 1C  is a block diagram of a touch screen system for touch pressure sensing. 
           [0013]      FIG. 1D  is illustrates a portion of a capacitive touch matrix for touch pressure sensing. 
           [0014]      FIG. 2A  is a schematic block diagram of an embodiment of an electronic device capable of acquiring touch data in a correlated fashion, in accordance with this disclosure. 
           [0015]      FIG. 2B  is a schematic block diagram of another embodiment of an electronic device capable of acquiring touch data in a correlated fashion, in accordance with this disclosure. 
           [0016]      FIG. 3  is a schematic block diagram of an embodiment of the touch and force sensors of  FIGS. 2A and 2B  that illustrates the different sensing layers thereof. 
           [0017]      FIG. 4  is a timing diagram showing acquisition times of the touch and force sensors of  FIGS. 2A and 2B  in a first mode of operation. 
           [0018]      FIG. 5  is a timing diagram showing acquisition times of the touch and force sensors of  FIGS. 2A and 2B  in a second mode of operation. 
           [0019]      FIG. 6  is a timing diagram showing acquisition times of the touch and force sensors of  FIGS. 2A and 2B  in a third mode of operation. 
           [0020]      FIG. 7  is a timing diagram showing acquisition times of the touch and force sensors of  FIGS. 2A and 2B  in a fourth mode of operation. 
           [0021]      FIG. 8  is a timing diagram showing acquisition times of the touch and force sensors of  FIGS. 2A and 2B  in a fifth mode of operation. 
           [0022]      FIG. 9  is a timing diagram showing generation of drive signals for the touch and force sensors in response to a synchronization signal, when operating according to the fifth mode of operation. 
           [0023]      FIG. 10  is another timing diagram showing generation of drive signals for the touch and force sensors in response to a synchronization signal, when operating according to the fourth mode of operation. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    The present description is made with reference to the accompanying drawings, in which example embodiments are shown. However, many different embodiments may be used, and thus the description should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete. Like numbers refer to like elements throughout, and prime notation is used to indicate similar elements in alternative embodiments. 
         [0025]    Reference is now made to  FIG. 1A  showing a portion of a capacitive touch matrix  10  for touch location sensing comprising a plurality of conductive rows  12  and plurality of conductive columns  14 . Each row  12  and column  14  is formed by a plurality of serially connected diamond shaped regions  16  forming a conductive line or trace. The conductive rows  12  and the conductive columns  14  cross above or below each other at intersection points, but are not in electrical contact with one another. Because of the diamond pattern, the conductive rows  12  and the conductive columns  14  are separated from each other by capacitive gaps  18 . The diamond pattern may provide decreased capacitance between conductive rows  12  and conductive columns  14 . Capacitive touch matrix  10  may sense an object that modifies the fringing electric field above the capacitive gaps  18  when the object is in contact or in proximity to the matrix  10 . 
         [0026]      FIG. 1B  shows that when a conductive row  12  and a conductive column  14  are selected by the switch matrices  44  and  46 , the total capacitance of a capacitance sensor formed between row and column conductors is the sum of four capacitances  20  between the four adjacent diamond-shaped regions  16  of the selected row and column. The mutual capacitance of the capacitance sensor between the selected row  12  and column  14  conductors can be sensed to determine whether an object is in contact with or in proximity to the matrix  10  above the region in which the four capacitances  20  are formed. Each conductive row  12  and conductive column  14  of the capacitive touch matrix  10  may be selected in succession to sense the capacitances at each intersection position of the touch matrix. 
         [0027]    Shown in  FIG. 1D  is a portion of a touch screen system  100  including the capacitive touch matrix  10  (for sensing touch location), and a capacitive touch force matrix  209  (for sensing touch pressure). The capacitive touch force matrix  209  includes columns and rows that are spaced apart vertically by a compressible layer but cross one another. The pressure of a user&#39;s finger on a touch screen incorporating the capacitive touch force matrix  209  changes the distance between the rows and columns, and thus changes the capacitance between the two. 
         [0028]      FIG. 1C  is a block diagram of a touch screen system  100  that includes the capacitive touch matrix  209  and an associated touch force IC  120 . The touch force IC  120  includes a row switch matrix  244  and a column switch matrix  246  for selection of rows and columns of the capacitive touch force matrix, such selection being made to select a particular mutual capacitance within the matrix  209  for sensing. The column switch matrix  246  receives a drive signal generated by a driver  248  and selectively applies the drive signal in a sequential manner to each of the columns C 1 -C 4 . The row switch matrix  244  sequentially selects one or more of the rows R 1 -R 3  for connection to a capacitance-to-digital converter circuit  250  that operates to sense charge of the mutual capacitance between rows R 1 -R 3  and columns C 1 -C 4  of the capacitive touch matrix  209  and convert that sensed charge to a digital value for output. 
         [0029]    With additional reference to  FIGS. 2A-2B , further details of the touch screen system  100  are now given. The touch screen system  100  may be incorporated into any suitable electronic device, such as a smartphone, tablet, smartwatch, laptop, or vehicle infotainment system. The touch screen system  100  includes a host device  102  for interfacing with the processor or system on a chip (SoC) of the electronic device, a touch location IC  110  for operating and acquiring touch location data from touch sensors  130  (which include the capacitive touch matrix  10 ), and a touch force IC  120  for operating and acquiring touch force data from touch force sensors  140  (which include a capacitive touch matrix similar to the capacitive touch force matrix  209 ). 
         [0030]    The touch IC  110  includes a touch screen controller  112  in bidirectional communication with the host device  102 . The touch screen controller  112  operates the touch analog front end  114 , which includes the various components of the touch IC  110  described above. Similarly, the force IC  120  includes a force controller  122  in bidirectional communication with the host device  102 . The force controller  122  operates the force analog front end  124 , which includes components similar to those described above with respect to the touch force IC  209 . 
         [0031]    Either the touch controller  112  or force controller  122  of the embodiment shown in  FIG. 2A , in operation, generates a synchronization signal, which is fed to the other through the host  102 . The function of this synchronization signal will be described in detail below. 
         [0032]    An alternative embodiment is shown in  FIG. 2B  in which the force IC  120 ′ lacks an on-chip touch controller, and instead the touch controller  112  of the touch IC itself  110  also functions as the touch controller for the force IC  120 ′. Here, the touch controller  112  generates the synchronization signal and feeds it directly to the force IC  120 ′. 
         [0033]    The touch sensor  130 , as shown in  FIG. 3 , makes up an upper sensing layer, and illustratively includes four touch sensors or touch sensor regions  130   a - 130   d.  The touch force sensor  140  makes up a lower sensing layer, and illustratively includes two force sensors or force sensor regions  140   a - 140   b.  It should be noted that the force sensors  140   a - 140   b  are larger than the touch sensors  130   a - 130   d,  meaning that the touch sensor  130  has a different pitch (which here is greater, but may in some applications possibly be less) than that of the force sensor  140 . 
         [0034]    The synchronization signal can be used by the touch IC  110  and force IC  120  in a variety of operation modes to provide for data acquisition in a fashion such that data from each touch sensor  130   a - 103   d  and each touch force sensor  140   a - 140   b  is correlated and consistent. 
         [0035]    In one operation mode, which can be referred to as a cell synchronization mode, data from the touch sensors  130   a - 130   d  is each acquired in order by the touch controller  122 , beginning in response to a transition of the synchronization signal. This is shown in the timing diagram of  FIG. 4 . When touch location data is acquired sequentially from touch sensors  130   a - 130   b,  at times T 1  and T 2 , touch force data is simultaneously acquired from the force sensor  140   a  (which is vertically aligned with touch sensors  130   a - 130   b ) also at times T 1  and T 2 . Similarly, when touch location data is acquired sequentially from touch sensors  130   c - 130   d  (which is vertically aligned with force sensor  140   b ), at times T 3  and T 4 , touch force data is simultaneously acquired from the force sensor  140   b  (at each acquisition of touch location data), also at times T 3  and T 4 . 
         [0036]    In an alternate cell synchronization mode, data from the touch sensors  130   a - 130   d  is each acquired in order by the touch controller  122 , beginning in response to a transition of the synchronization signal. This is shown in the timing diagram of  FIG. 5 . When touch location data is acquired from touch sensor  130   a  at time T 1 , touch force data is simultaneously acquired from the force sensor  140   a  (which is vertically aligned with the touch sensor  130   a ) also at time T 1 . Similarly, when touch location data is acquired sequentially from touch sensor  130   c  at time T 3 , touch force data is simultaneously acquired from the force sensor  140   b  (which is vertically aligned with the touch sensor  130   c ) also at time T 3 . 
         [0037]    While touch force data is not acquired concurrently with touch location data acquisition at times T 2  and T 4 , provided that the rate of change of the touch location data and touch force data is substantially less than the acquisition rate thereof, accurate and correlated touch location and touch force data can be acquired this fashion while reducing power consumption due to cutting in half the number of touch force data acquisitions. 
         [0038]    In an alternate cell synchronization mode, data from the touch sensors  130   a - 130   d  is each acquired in order by the touch controller  122 , beginning in response to a transition of the synchronization signal. This is shown in the timing diagram of  FIG. 6 . When touch location data is acquired from touch sensor  130   a  and  130   b  at times T 1  and T 2 , touch force data is acquired from the force sensor  140   a  during a window of time shown starting at time F 1  and running from after the start of acquisition of touch location data at T 1  to before the end of acquisition of touch location data at T 2 . 
         [0039]    Similarly, when touch location data is acquired sequentially from touch sensor  130   c  and  130   d  at times T 3  and T 4 , touch force data is simultaneously acquired from the force sensor  140   b  during a window of time shown starting at time F 2  and running from after the start of acquisition of touch location data at T 3  to before the end of acquisition of touch location data at T 4 . 
         [0040]    While touch force data is not acquired during the entire acquisition times for the touch sensors  130   a - 130   d  and force sensors  140   a - 140   b  provided that the rate of change of the touch location data and touch force data is substantially less than the acquisition rate thereof, accurate and correlated touch and touch force data can be acquired this fashion while reducing power consumption due to cutting in half the number of touch force data acquisitions. 
         [0041]    In a further cell synchronization mode shown in  FIG. 7 , touch location data is acquired simultaneously from touch sensors  130   a - 130   b  and force sensor  140   a  at times T 1  and T 2 , and is acquired simultaneously from the touch sensors  130   c - 130   d  and force sensor  140   b  at times T 3  and T 4 . 
         [0042]    The matrix  10  level operation of this operation mode is now described with reference to the timing diagram shown in  FIG. 10 . As shown, at the falling edge of the sync signal at time T 1 , drive signals to touch sensors  130   a - 130   b  are pulsed in a synchronized fashion, and a drive signal to force sensor  140   a  is pulsed (at a much lower frequency) in a synchronized fashion with the drive signals to touch sensors  130   a - 130   b.  Concurrent with the pulsing of these various drive signals, the appropriate sense lines are sensed to as to acquire the touch location data and the touch force data. As also shown, at the next falling edge of the sync signal at time T 2 , drive signals to touch sensors  130   c - 130   d  are pulsed in a synchronized fashion, and a drive signal to force sensor  140   b  is pulsed (at a much lower frequency) in a synchronized fashion with the drive signals to touch sensors  130   c - 130   d.    
         [0043]    In a further mode shown in  FIG. 8 , which can be referred to as a frame synchronization mode, in response to a transition of the synchronization signal, each touch sensor  130   a - 130   d  and each touch force sensor  140   a - 140   b  are respectively operated by the touch controller  112  and force controller  122  to simultaneously acquire a frame of data. In this way, the resulting acquired touch location data and touch force data is correlated, and the touch force data accurately corresponds to the pressure or force exerted by a user&#39;s finger on a display employing the touch screen system  100 . Where the touch sensor  130  and force sensor  140  have different acquisition times, the slower acquisition time controls and the synchronization signal is generated so as to permit proper function. 
         [0044]    A sample timing diagram for this frame synchronization mode is shown in  FIG. 9 . As shown, data is simultaneously acquired by the touch sensors  130   a - 130   d  and the force sensors  140   a - 140   b  at time T 1 . 
         [0045]    The matrix  10  level operation of this operation mode is now described with reference to the timing diagram shown in  FIG. 8 . As shown, at the falling edge of the sync signal at time T 1 , drive signals to the touch sensors  130   a - 130   d  are pulsed in a synchronized fashion, and drive signals to force sensors  140   a - 140   b  are pulsed (at a much lower frequency) in a synchronized fashion with the drive signals to touch sensors  130   a - 130   d.  Concurrent with the pulsing of these various drive signals, the appropriate sense lines are sensed to as to acquire the touch location data and the touch force data. 
         [0046]    Many modifications and other embodiments will come to the mind of one skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is understood that various modifications and embodiments are intended to be included within the scope of the appended claims.