PATENT DOCUMENT

Publication Number: US-10152187-B2
Application Number: US-201715627058-A
Country: US
Kind Code: B2

Title: Electronic device with an integrated touch sensing and force sensing device

Abstract:
An integrated touch sensing and force sensing device is included in an electronic device. The integrated touch sensing and force sensing device includes a force-sensitive layer operably attached to an input surface, a first electrode layer attached to a first surface of the force-sensitive layer, and a second electrode layer attached to a second surface of the force-sensitive layer. An analog front end processing channel is operable to process a touch signal that is based on a change in an electrical property between the first and second electrode layers and operable to process a force signal that is based on an electrical property generated by the force-sensitive layer based on a force applied to the input surface.

Claims:
What is claimed is: 
     
       1. A method of power management in an integrated touch-sensing and force-sensing device, the method comprising:
 detecting, at a force-sensitive layer of the integrated touch sensing and force sensing device, a force input to the integrated touch sensing and force sensing device while a touch-sensing operation of the integrated touch sensing and force sensing device is disabled; 
 enabling the touch-sensing operation in response to detecting the force input; and 
 detecting a touch input to the integrated touch sensing and force sensing device by detecting a change in an electrical property between a first electrode layer attached to a first surface of the force-sensitive layer and a second electrode layer attached to a second surface of the force-sensitive layer opposite the first surface. 
 
     
     
       2. The method of  claim 1 , wherein:
 detecting the force input comprises:
 processing the force input by a force processing channel to produce a force signal; and 
 determining that the force signal equals or exceeds a threshold value; and 
 
 enabling the touch-sensing operation in response to detecting the force input comprises:
 enabling the touch-sensing operation when the force signal equals or exceeds the threshold value. 
 
 
     
     
       3. The method as in  claim 1 , further comprising processing a touch signal based on the touch input to the integrated touch sensing and force sensing device. 
     
     
       4. The method of  claim 3 , further comprising:
 disabling the touch-sensing operation after processing the touch signal. 
 
     
     
       5. The method of  claim 1 , wherein enabling the touch-sensing operation comprises enabling circuitry in a touch processing channel. 
     
     
       6. The method of  claim 5 , wherein enabling circuitry in the touch processing channel comprises transitioning the circuitry from an off or lower power state to an operational state. 
     
     
       7. The electronic device of  claim 1 , wherein the first surface is opposite the second surface. 
     
     
       8. The electronic device of  claim 1 , wherein the force-sensitive layer comprises a piezoelectric layer. 
     
     
       9. The electronic device of  claim 1 , wherein the first and second electrode layers form a capacitive sensor. 
     
     
       10. The electronic device of  claim 1 , wherein the at least one of the first or second electrode layers is conductively coupled to the force-sensitive layer. 
     
     
       11. An electronic device, comprising:
 an integrated touch sensing and force sensing device, comprising:
 an input surface; 
 a force-sensitive layer attached to the input surface; 
 a first electrode layer attached to a first surface of the force sensitive layer; and 
 a second electrode layer attached to a second surface of the force-sensitive layer; and 
 
 an analog front end (AFE) processing channel operably connected to the integrated touch sensing and force sensing device, the AFE processing channel comprising:
 a touch processing channel configured to process a touch signal that is based on a change in an electrical property between the first and second electrode layers; and 
 a touch power management channel configured to detect a force applied to the force-sensitive layer and, in response, enable a touch-sensing operation of the integrated touch sensing and force sensing device. 
 
 
     
     
       12. The electronic device of  claim 11 , wherein the force-sensitive layer comprises a piezoelectric layer. 
     
     
       13. The electronic device of  claim 11 , wherein enabling the touch-sensing operation comprises enabling circuitry of the touch processing channel. 
     
     
       14. The electronic device of  claim 13 , wherein enabling circuitry of the touch processing channel comprises transitioning the circuity from an off or lower power state to an operational state. 
     
     
       15. The electronic device of  claim 11 , wherein the touch power management channel comprises a comparator configured to compare a force signal corresponding to the force applied to the force sensitive layer to a threshold value, and to enable the touch-sensing operation based on the comparison. 
     
     
       16. The electronic device of  claim 11 , wherein:
 the first electrode layer comprises a set of discrete electrodes; 
 the AFE processing channel further comprises a receiver AFE channel operably connected to at least one respective discrete electrode in the set of discrete electrodes; 
 the touch processing channel is operably connected to a first output of the AFE receiver channel; and 
 the touch power management channel is operably connected to a second output of the AFE receiver channel. 
 
     
     
       17. The electronic device of  claim 16 , wherein enabling the touch-sensing operation comprises enabling circuitry of the touch processing channel or the receiver AFE channel. 
     
     
       18. The electronic device of  claim 17 , wherein enabling circuitry of the touch processing channel comprises transitioning the circuity from an off or lower power state to an operational state. 
     
     
       19. The electronic device of  claim 17 , wherein the touch processing channel comprises:
 a demodulator operably connected to the first output of the AFE receiver channel; and 
 an accumulator operably connected to an output of the demodulator; 
 wherein the enabled circuitry of the touch processing channel comprises the demodulator and the accumulator. 
 
     
     
       20. The electronic device of  claim 11 , wherein the touch power management channel is further configured to disable the touch-sensing operation after touch signal processing.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 14/498,556, filed on Sep. 26, 2014, and entitled “Electronic Device with an Integrated Touch Sensing and Force Sensing Device,” which is incorporated by reference as if fully disclosed herein. 
    
    
     TECHNICAL FIELD 
     The present invention relates generally to electronic devices, and more specifically to an electronic device that includes an integrated touch sensing and force sensing device. 
     BACKGROUND 
     Touch displays have become increasingly popular in electronic devices. Smart phones, cell phones, tablet computers, notebook computers, and computer monitors, and so forth, are increasingly equipped with displays 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. 
     Touch sensitive devices generally provide position identification of where the user touches the device. A touch may include movement, gestures, and other effects related to position detection. For example, touch sensitive devices can provide information to a computing system regarding user interaction with a graphical user interface (GUI) of a display, such as pointing to elements, reorienting or repositioning elements, editing or typing, and other GUI features. In another example, touch sensitive devices can provide information to a computing system for a user to interact with an application program, such as relating to input or manipulation of animation, photographs, pictures, slide presentations, sound, text, other audiovisual elements, and so forth. 
     While the touch sensitive devices provide an input mechanism that provides an appearance that the user is interacting directly with element displayed in the GUI, the input is generally limited to the x-, y-positioning of the touch. In some cases, the input sensitivity has been increased to allow for multi-touch inputs, but this is still limited to positional constraints of the surface upon which the touch is sensed. Some applications and programs may benefit from additional input modes beyond that provided strictly by the touch sensing. 
     SUMMARY 
     In one aspect, an integrated touch sensing and force sensing device is included in an electronic device. The integrated touch sensing and force sensing device includes a force-sensitive layer attached to an input surface, a first electrode layer attached to a first surface of the force-sensitive layer, and a second electrode layer attached to a second surface of the force-sensitive layer. One or more analog front end (AFE) processing channels is operably connected to the integrated touch sensing and force sensing device. Each AFE processing channel is configured to process a touch signal that is based on a change in an electrical property between the first and second electrode layers and operable to process a force signal that is based on an electrical property generated by the force-sensitive layer based on a force applied to the input surface. In one embodiment, the force-sensitive layer is made of a piezoelectric material. The touch signal, for example, may be based on a change in a capacitance between the first and second electrode layers. 
     In some embodiments, an AFE processing channel may include a receiver AFE channel operably connected to one electrode layer in the integrated touch sensing and force sensing device. A touch processing channel and a force processing channel may each be operably connected to an output of the receiver AFE channel. A touch transmitter channel can be operably connected to the other electrode layer in the integrated touch sensing and force sensing device. In some embodiments, a servo/sigma delta analog-to-digital converter is included in the receiver AFE channel. 
     In some embodiments, a mechanical oscillator may be operably connected to the force-sensitive layer in the integrated touch sensing and force sensing device The mechanical oscillator may modulate the force applied to the force-sensitive layer. A separate demodulator channel can demodulate the amplitude modulated charge from the force-sensitive layer. 
     In some embodiments, a touch power management channel may be electrically connected to an output of the first analog-to-digital converter in the analog front end processing channel. The touch power management channel can receive signals from other analog front end channels. The power management channel can detect a force applied to the force-sensitive layer and in response enable a touch sensing operation. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the invention 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. 
         FIG. 1  is a conceptual cross-sectional view of a display screen that can be used for touch and force sensing operations; 
         FIG. 2  is a front view of one example of an electronic device that can include an integrated touch sensing and force sensing device; 
         FIG. 3  is an example block diagram of the electronic device shown in  FIG. 2 ; 
         FIG. 4  is a simplified cross-section view of the electronic device taken along line  4 - 4  in  FIG. 1 ; 
         FIGS. 5-10  depict various configurations of the first electrode layer  406  and the second electrode layer  408  shown in  FIG. 4 ; 
         FIG. 11  is a simplified schematic diagram of a first analog front end (AFE) processing channel that may be operably connected to a force-sensitive layer of an integrated touch sensing and force sensing device; 
         FIG. 12  is a simplified schematic diagram of a second analog front end processing channel that may be operably connected to a force-sensitive layer of an integrated touch sensing and force sensing device; 
         FIG. 13  depicts an example schematic diagram of the sigma delta analog-to-digital converter  1200  shown in  FIG. 12 ; 
         FIG. 14  is a simplified schematic diagram of a first processing channel shared by the integrated touch sensing and force sensing device; 
         FIG. 15  is a simplified schematic diagram of a second processing channel shared by the integrated touch sensing and force sensing device; 
         FIG. 16  is a simplified schematic diagram of a third processing channel shared by the integrated touch sensing and force sensing device; 
         FIG. 17  is a simplified schematic diagram of a fourth processing channel shared by the integrated touch sensing and force sensing device; 
         FIG. 18  is a flowchart of a method of power management in an integrated touch sensing and force sensing device; and 
         FIG. 19  is a simplified schematic diagram of a fifth processing channel shared by the integrated touch sensing and force sensing device. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments herein are described in conjunction with a display in an electronic device that includes an integrated touch sensing and force sensing device. Other embodiments, however, are not limited to this implementation. An integrated touch sensing and force sensing device can be included in a different component in or connected to an electronic device. As one example, an integrated touch sensing and force sensing device can be incorporated into an enclosure of an electronic device. Additionally or alternatively, an integrated touch sensing and force sensing device can be included in an input device, such as a track pad or mouse. 
     Embodiments of the integrated touch sensing and force sensing device may be used with multi-touch enabled devices. The integrated touch sensing and force sensing device is adapted to resolve force on a touch sensing element basis. In some embodiments, a piezoelectric film is included in a touch sensing device and used to determine an amount of force applied to an input surface of the touch sensing device. The piezoelectric film can create a charge that is a function of the applied force due to the strain on the piezoelectric material. A touch processing channel and a force processing channel are operatively connected to the integrated touch sensing and force sensing device and may share circuitry that processes both touch and force inputs. 
     Referring now to  FIG. 1 , there is shown a conceptual cross-sectional view of a display that can be used for touch and force sensing operations. The functions can include a display function  100 , a touch sensing function  102 , and a force sensing function  104 . These functions can be performed in conjunction with the display  106 . In other words, a user can interact with a viewable image on the display  106  with one or more touches, an applied force, or both touch and force. For example, a game that is displayed on the display  106  can receive touch inputs from a user. As another example, an application displayed on the display  106  can perform one function at one rate of speed when a user applies a small amount of force to the display and perform the function at a faster rate of speed when the user applies a greater amount of force to the display  106 . 
     The touch sensing and force sensing functions can each use or share some or all of the display area. For example, in one embodiment, a user can interact with a displayed image by touching and/or by applying a force at an appropriate position on the display, with the appropriate position located anywhere on the display. In another embodiment, the display function  100  and the touch sensing function  102  can use the entire display  106  while the force sensing function  106  involves a portion of the display  106 . Thus, each function can use some or all of the display  106  when in operation. The arrangement of the functions in  FIG. 1  is for illustrative purposes only, and does not correspond to any layers or devices in the display or in an electronic device. Additionally, the arrangement of the functions does not correspond to the amount of area on the display used by each function. 
       FIG. 2  is a front view of one example of an electronic device that can employ an integrated touch sensing and force sensing device. In the illustrated embodiment, the electronic device  200  is implemented as a smart telephone. Other embodiments can implement the electronic device differently, such as, for example, as a laptop computer, a tablet computing device, a wearable communication device, a digital music player, a kiosk, a remote control device, and other types of electronic devices that include an integrated touch sensing and force sensing device. 
     The electronic device  200  includes an enclosure  202  surrounding a display  204  and one or more buttons  206  or input devices. The enclosure  202  can form an outer surface or partial outer surface and protective case for the internal components of the electronic device  200 , and may at least partially surround the display  204 . The enclosure  202  can be formed of one or more components operably connected together, such as a front piece and a back piece. Alternatively, the enclosure  202  can be formed of a single piece operably connected to the display  204 . 
     The display  204  can be implemented with any suitable display, including, but not limited to, a multi-touch sensing touchscreen device that uses liquid crystal display (LCD) technology, light emitting diode (LED) technology, organic light-emitting display (OLED) technology, or organic electro luminescence (OEL) technology. 
     The button  206  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  206  can be integrated as part of a cover glass of the electronic device. Additionally or alternatively, the electronic device  200  can include other types of input devices. Example input devices include, but are not limited to, a microphone, a trackpad, a communication or network port, and one or more buttons. 
     Referring now to  FIG. 3 , there is shown an example block diagram of the electronic device  200  shown in  FIG. 2 . The electronic device  200  can include the display  204 , a processing device  300 , a power source  302 , a memory or storage device  304 , a sensor  306 , and an input/output  308  (e.g., input/output device and/or an input/output port). The processing device  300  can control some or all of the operations of the electronic device  200 . The processing device  300  can communicate, either directly or indirectly, with substantially all of the components of the electronic device  200 . For example, a system bus or other communication mechanism  310  can provide communication between the processing device  300 , the power source  302 , the memory  304 , the sensor  306 , and/or the input/output  308 . 
     The processing device  300  can be implemented as any electronic device capable of processing, receiving, or transmitting data or instructions. For example, the processing device  300  can be a microprocessor, a central processing unit (CPU), an application-specific integrated circuit (ASIC), a digital signal processor (DSP), or combinations of such devices. As described herein, the term “processing device” is meant to encompass a single processor or processing unit, multiple processors, multiple processing units, or other suitably configured computing element or elements. 
     It should be noted that the components of the electronic device can be controlled by multiple processing devices. For example, select components of the electronic device  200  may be controlled by a first processing device and other components of the electronic device  200  may be controlled by a second processing device where the first and second processing devices may or may not be in communication with each other. 
     The power source  302  can be implemented with any device capable of providing energy to the electronic device  200 . For example, the power source  302  may be one or more batteries or rechargeable batteries. Additionally or alternatively, the power source can be a power cord that connects the electronic device to another power source such as a wall outlet. 
     The memory  304  can store electronic data that can be used by the electronic device  200 . For example, a memory can store electrical data or content such as, for example, audio and video files, documents and applications, device settings and user preferences, timing signals, control signals, and data structures or databases. The memory  304  can be configured as any type of memory. By way of example only, the memory can be implemented as random access memory, read-only memory, Flash memory, removable memory, or other types of storage elements, or combinations of such devices. 
     The electronic device  200  may also include one or more sensors  306  positioned substantially anywhere on the electronic device  200 . The sensor(s)  306  can be configured to sense substantially any type of characteristic, such as but not limited to, pressure, light, touch, heat, movement, relative motion, biometric data, and so on. For example, the sensor(s)  306  may be a heat sensor, a position sensor, a light or optical sensor, an accelerometer, a pressure transducer, a gyroscope, a magnetometer, a health monitoring sensor, and so on. Additionally, the one or more sensors  306  can utilize any suitable sensing technology, including, but not limited to, capacitive, ultrasonic, resistive, optical, ultrasound, piezoelectric, and thermal sensing technology. 
     The input/output  308  can transmit and/or receive data from a user or another electronic device. The I/O device(s) can include a display, a touch sensing input surface such as a track pad, one or more buttons (e.g., button  206 ), one or more cameras, one or more microphones or speakers, one or more ports such as a microphone port, and/or a keyboard. Additionally or alternatively, an I/O device or port can transmit electronic signals via a communications network, such as a wireless and/or wired network connection. Examples of wireless and wired network connections include, but are not limited to, cellular, Wi-Fi, Bluetooth, IR, and Ethernet. 
     A touch controller  312  includes touch processing channel  314  and force processing channel  316 . The touch controller  312  is operably connected to the display  204 . In particular, the touch controller  312  is configured to transmit and receive signals from the touch sensing and force sensing device included in the display  204 . The touch processing channel  314  and the force processing channel  316  can share circuitry when processing signals received from the integrated touch sensing and force sensing device. 
     It should be noted that  FIG. 1-3  are exemplary only. In other examples, the electronic device may include fewer or more components than those shown in  FIGS. 1-3 . Additionally, as described earlier, an integrated touch sensing and force sensing device may be incorporated into substantially any type of device. Additionally or alternatively, an integrated touch sensing and force sensing device can be included in any type of component within, or connected to an electronic device. 
       FIG. 4  is a simplified cross-section view of the electronic device taken along line  4 - 4  in  FIG. 2 . The integrated touch sensing and force sensing device  400  can include an input surface  402  and a force-sensitive layer  404 . The input surface  402  may be an exterior surface, such as a cover glass disposed over the top surface of the electronic device. The input surface  402  is substantially transparent in the illustrated embodiment. 
     The force-sensitive layer  404  is disposed below the input surface  402 . The force-sensitive layer  404  can be attached to the input surface  402  with an optically clear adhesive (not shown). The force-sensitive layer  404  is typically a compliant material that exhibits an electrical property that is variable in response to deformation or deflection of the layer. The force-sensitive layer may be formed from a piezoelectric, piezo-resistive, resistive, or other strain-sensitive materials. The force-sensitive layer  404  is a piezoelectric layer in the embodiments described herein. The piezoelectric layer generates a localized electric charge in response to a deformation of the piezoelectric layer. 
     A first electrode layer  406  is attached to a first surface of the force-sensitive layer  404  and a second electrode layer  408  is attached to an opposing second surface of the force-sensitive layer  404 . In the illustrated embodiment, the electrodes can be formed from a transparent conductive material, such as an indium tin oxide (ITO). As will be described in more detail later, one electrode layer can be connected to drive circuitry that applies a stimulus signal to the electrode layer. Another electrode layer can be connected to sense circuitry capable of detecting one or more touches and an amount of electric charge generated by the piezoelectric layer  404 . 
     A display layer  410  can be attached to the integrated touch sensing and force sensing device  400 . The display layer may take a variety of forms, including as a liquid crystal display (LCD), a light-emitting diode (LED) display, an organic light-emitting diode (OLED) display, or the like, for generating images to be displayed by the electronic device. The display layer  410  can be coupled to the piezoelectric layer  404  and/or to the second electrode layer  408  by an optically clear adhesive (not shown). Since the materials above the display layer  410  may be formed from transparent materials, images generated by the display layer  410  can be viewed through the materials positioned above the display layer. 
     In the illustrated embodiment, a touch sensing device is formed by the first and second electrodes  406 ,  408 . The touch sensing device can detect touch using any suitable sensing technology. Example touch sensing technologies include, but are not limited to, capacitive, ultrasound, resistive, and optical sensing technologies. As one example, the integrated touch sensing and force sensing device  400  can detect one or more touches based on capacitance differences between a finger and an electrode layer, or based on capacitance differences between the first and second electrode layers  406 ,  408 . Sense circuitry connected to one electrode layer is scanned to measure a capacitance between the first and second electrode layers. 
     For force detection, as a user applies a downward force on the input surface  402 , the input surface  402  can deform by an amount corresponding to an amount of the applied force. The deformation of the input surface  402  may cause a corresponding deformation in the piezoelectric layer  404 . The piezoelectric layer  404  can then generate an amount of electric charge based on the amount of deformation of the layer. The generated electric charge may be received by the sense circuitry via the electrode layer attached to the sense circuitry. Since the amount of electric charge generated by the piezoelectric layer  404  can be representative of the amount of deformation of the piezoelectric layer, and because the amount of deformation of the piezoelectric layer may be representative of the force applied to the input surface  402 , the amount of electric charge detected by the sense circuitry can be representative of the force applied to the input surface  402 . In this way, the sense circuitry can be used to detect an amount of force applied to the input surface  402 . 
     The first and second electrode layers  406 ,  408  may each include a single electrode or multiple electrodes.  FIGS. 5-10  depict various configurations of the first electrode layer  406  and the second electrode layer  408  shown in  FIG. 4 . In  FIGS. 5 and 6 , the second electrode layer  408  extends along the surface of the piezoelectric layer  404  and may have a shape that substantially matches the shape of the piezoelectric layer  404 . The first electrode layer  406  includes multiple discrete electrodes extending along the surface of the piezoelectric layer  404 . While  FIG. 5  shows the first electrode layer  406  having twenty-five discrete electrodes arranged in rows and columns, the first electrode layer  406  can have any number of discrete electrodes having any desired shape and arranged in any given pattern. When the first electrode layer is patterned into discrete electrodes, the location or locations of a touch on the input surface  402  can be determined. Additionally, the location and the amount of force applied to the input surface  402  can be determined. 
     When the first and second electrodes are configured as shown in  FIGS. 5 and 6 , the first electrode layer  406  is the sense layer and a reference voltage (e.g., ground) is applied to the second electrode layer  408 . A self-capacitance analog front end processing channel can be used in conjunction with the first electrode layer shown in  FIG. 5 , with the second electrode layer  408  acting as the ground return for the force sensing device. In some embodiments, the first electrode layer  406  shown in  FIG. 5  may be implemented into the V COM  layer of a display, such as the V COM  layer in an in-cell touchscreen display. Additionally, the force-sensitive layer  404  ( FIG. 4 ) may replace the layer in the in-touch touchscreen display stack that is adjacent to the V COM  layer to form an in-cell touch and force sensor. 
     Both the first and second electrode layers  406 ,  408  include multiple discrete electrodes in  FIGS. 7 and 8 . The discrete electrodes can extend along the surfaces of the piezoelectric layer  404 . Again, while  FIGS. 7 and 8  show the first and second electrode layers  406 ,  408  each having twenty-five discrete electrodes arranged in rows and columns, the first and second electrode layers can each have any number of discrete electrodes having any desired shape and arranged in any given pattern. When the first and second electrode layers are patterned into discrete electrodes, the location of multiple touches on the input surface  402  can be determined. Additionally, the location and the amount of multiple forces applied to the input surface  402  can be determined. 
     When the first and second electrodes are configured as shown in  FIGS. 7 and 8 , the discrete electrodes in one electrode layer (e.g., the first electrode layer  406 ) are the sense electrodes and a reference voltage (e.g., ground) is applied to the discrete electrodes in the other electrode layer (e.g., the second electrode layer  408 ). Similar to  FIG. 5 , a self-capacitance analog front end processing channel can be used in conjunction with the sense electrodes (e.g., the first electrode layer) with the other electrode layer (e.g., the second electrode layer) acting as a per electrode ground return for the force sensing device. 
     In  FIGS. 9 and 10 , the first electrode layer  406  may be patterned into discrete rows of electrodes. The second electrode layer  408  can be patterned into discrete columns of electrodes. The first and second electrode layers  406 ,  408  are used in a mutual capacitance mode. Charge between the electrode rows and the electrode columns can be measured at each intersection of an electrode row and an electrode column. When the first and second electrodes are patterned into discrete electrodes, the location of multiple touches on the input surface  402  can be determined. Additionally, the location and the amount of multiple forces applied to the input surface  402  can be determined. While  FIGS. 9 and 10  show the first and second electrode layers each having five rectangular discrete electrodes arranged in rows and columns, respectively, in other embodiments the first and second electrode layers can have any number of discrete electrodes having any desired shape and arranged in any given pattern. 
     The display layer  410  is not included in those embodiments that include an integrated touch sensing and force sensing device in a component other than in the display, such as in an enclosure, an input device (e.g., button or a track pad). In one embodiment, a substrate (not shown) may be disposed below the sense layer. The substrate may be substantially any support surface, such as a portion of a printed circuit board, the enclosure, or the link. Additionally, the substrate may be configured to surround or at least partially surround one or more sides of the integrated touch sensing and force sensing device. 
     Referring now to  FIG. 11 , a simplified schematic of an analog front end (AFE) processing channel is shown. In one embodiment, one or more AFE processing channels is operably connected to an integrated touch sensing and force sensing device  1100 . An AFE processing channel can include an integration capacitor  1102  and an AFE  1104 . In the illustrated embodiment, the AFE  1104  includes an amplifier  1106 , a low-pass filter  1108 , and a nyquist ADC  1110  (e.g., SAR or similar). In some embodiments, the integration capacitor  1102  can be sufficiently large in size to make implementing the capacitor into an ASIC impractical. Therefore, in some embodiments, the integration capacitor  1102  and the AFE  1104  in  FIG. 11  can be replaced with a sigma-delta ADC  1200  (see  FIG. 12 ). Instead of accumulating the charge by the integration capacitor  1302 , charge is continuously digitized and digitally accumulated using sigma-delta techniques. The sigma-delta ADC includes the functions of the low-pass filter  1108  shown in  FIG. 11 . The quantizer in the sigma-delta ADC can have lower resolution than that of the ADC  1110  while not compromising dynamic range. While the quantizer resolution is smaller, and thus its quantization noise is higher than that of the nyquist ADC  1110 , the quantization noise is shaped by the feedback loop in the sigma-delta ADC and pushed toward higher frequencies at 6 dB per octave, for example, for a 1 st  order sigma delta ADC. The decimation filter performs the digital accumulation function while removing the shaped quantization noise, which can improve the dynamic range of the measurement. 
     In some embodiments, a first charge is obtained when a force is applied to the piezoelectric layer, and second charge is obtained when the force on the piezoelectric layer is released. The second charge has a polarity that is opposite to the polarity of the first charge. Thus, integration of the charge may be needed to determine the full or absolute force applied to the piezoelectric layer 
     
       
         
           
             
               ( 
               
                 
                   F 
                   ⁡ 
                   
                     ( 
                     t 
                     ) 
                   
                 
                 = 
                 
                   
                     1 
                     ∝ 
                   
                   ⁢ 
                   
                     ∫ 
                     
                       
                         Q 
                         ⁡ 
                         
                           ( 
                           t 
                           ) 
                         
                       
                       ⁢ 
                       dt 
                     
                   
                 
               
               ) 
             
             . 
           
         
       
     
     In one embodiment, sigma-delta ADC  1200  can be a first order sigma-delta ADC. In another embodiment sigma-delta ADC  1200  can be a second or higher order sigma-delta ADC. Additionally, components other than the components shown in  FIG. 12  may be included in an analog front end processing channel. 
       FIG. 13  depicts an example schematic diagram of the sigma delta analog-to-digital converter  1200  shown in  FIG. 12 . The analog front end processing channel  1300  includes a summing circuit  1302  operably connected to the piezoelectric layer in the integrated touch sensing and force sensing device  1100 , and an input of an amplifier  1304  operably connected to an output of the summing circuit  1302 . The other input of the amplifier  1304  is operably connected to a bias voltage. A feedback capacitor  1306  is connected between an output of the amplifier  1304  and the input of the amplifier. Amplifier  1304  and capacitor  1306  form an integrator  1305 . An input of an analog-to-digital converter (ADC)  1308  is operably connected to the output of the amplifier  1304 . An input of a feedback current digital-to-analog converter (DAC)  1310  is operably connected to the output of a flip flop  1312 , and an output of the feedback current DAC  1310  is operably connected to an input of the summing circuit  1302 . An input of the flip-flop  1312  (e.g., D input) is operably connected to the output of the ADC  1308 . The clock (CLK) input of the flip-flop  1312  is connected to a sample clock signal FS. Although only one flip-flop  1312  is shown in  FIG. 13 , embodiments can use one or more flip-flops. The number of flip-flops included in the sigma delta ADC  1200  may be dependent upon the resolution of the ADC  1308 . For example, when the ADC is a 1-bit ADC, a single flip flop can be used. As another example, when an N-bit ADC is used, and N is greater than one, 2 N−1  flip flops may be used. 
     The output of the flip-flop  1312  can be connected to a decimation filter  1314 . The decimation filter can be an N+1 order decimation filter, where N is the order of the sigma delta ADC. In some embodiments, the decimation filter can be a Cascaded Integrator Comb (CIC) or FIR type decimation filter. The ADC  1308  and the feedback current DAC  1310  can each have resolutions of one or more bits. 
     Charge from the piezoelectric layer in the integrated touch sensing and force sensing device  1100  is received by the integrator  1305 , which integrates the charge. The signal output from the integrator  1305  is converted to a digital signal by the ADC  1308 . The feedback current DAC  1310  converts the digital signal to an analog signal and the summing circuit  1302  subtracts the analog signal from the charge signal received from the piezoelectric layer. Thus, the amplifier  1304  integrates the charge received from the piezoelectric layer in the integrated touch sensing and force sensing device  1100 . 
     The ADC  1308  introduces a quantization error Q/SQRT(12), where Q is the least significant bit (LSB) size of the ADC. The quantization noise is shaped by the feedback loop of the sigma-delta ADC. The transfer function from the point of the ADC&#39;s quantization noise to the output includes the integrator in negative feedback configuration, such that the overall frequency response from the perspective of the quantization noise is that that of a high-pass filter of the same order as the integrator. Therefore, the quantization noise is pushed toward higher frequencies at 6 dB/octave for a first order sigma-delta ADC. The decimation filter  1314  filters out some (e.g., a majority) of the quantization noise, leading to a result on signal line  1316  that is proportional to the total integrated charge. The total integrated charge can then be correlated to force. 
     Referring now to  FIG. 14 , there is shown a simplified schematic diagram of a first processing channel shared by the integrated touch sensing and force sensing device. Force is detected by measuring a relative charge (dQ=∝·dF) in the illustrated embodiment. A touch transmitter channel  1400  is connected to a discrete electrode  1402  (e.g., a row electrode). When the electrode layer is patterned into discrete electrodes, each discrete electrode may be connected to a touch transmitter channel, or groups of discrete electrodes can be connected to a touch transmitter channel. 
     A receiver analog front end (AFE) channel  1404  is connected to the other electrode layer  1406  (e.g., a column electrode). As described earlier, the row and column electrodes  1402 ,  1406 , respectively, are connected to different surfaces of the piezoelectric layer  1408 . In the illustrated embodiment, the electrode  1402  is a drive electrode (e.g., included in electrode layer  408 ) and the electrode  1406  is the sense electrode (e.g., included in electrode layer  406 ). Other embodiments can use the electrode  1402  as the sense electrode and electrode  1406  as the drive electrode. 
     A touch processing channel  1410  receives the output signal from the receiver analog front end channel  1404 . A force processing channel  1412  also receives the output signal from the receiver analog front end channel  1404 . 
     The touch transmitter channel  1400  includes an amplifier  1414  connected to a resistor  1416 . The resistor  1416  is connected to the drive electrode  1402 . An ADC  1418  can digitize the voltage across resistor  1416 . The ADC  1418  can be a first or higher order sigma-delta ADC, a SAR ADC, or another type of ADC. A decimation filter and error correction circuit  1420  is connected to an output of the ADC  1418 . A stimulation signal circuit  1422  is provided to the input of the amplifier  1414 . As a non-limiting example, the stimulation signal circuit  1422  can be implemented with a numerically controlled oscillator. When a touch sensing operation is to be performed, the stimulation signal circuit  1422  is applied to the drive electrode  1402  and an electrical property (e.g., a capacitance) on the sense electrode  1406  is sensed. 
     The receiver AFE channel  1404  includes an amplifier  1426  connected to an anti-aliasing filter  1428 . An input of an ADC  1430  is connected to the output of the anti-aliasing filter  1428 . An input of the amplifier  1426  is connected to the sense electrode  1406 . A feedback capacitor  1432  is connected between an output of the amplifier  1426  and the input of the amplifier  1426 . 
     The touch processing channel  1410  includes a demodulator  1434  connected to an accumulator  1436 . The force processing channel  1412  includes an error comparator  1438  and a decimation filter and error correction circuit  1440 . The output of the ADC  1430  (representing column force results) is input into the error comparator  1438 . In the embodiment shown in  FIG. 14 , the receiver AFE channel  1404  is shared for touch data, force data, touch sensing, and force sensing. Composite touch and force signals output from the receiver AFE channel  1404  are processed separately by the touch processing and force processing channels  1410  and  1412 , respectively. 
     When a force is applied to an input surface of the integrated touch sensing and force sensing device, charge from the piezoelectric layer  1408  is measured on the drive electrode  1402  and on the sense electrode  1406 . For the drive electrode  1402 , the amplifier  1414  receives charge from the piezoelectric layer  1408 . The voltage VCM_TX across the resistor  1416  represents the force on the intersection  1442  of the row-column electrodes (VCM_TX=−f(Qpiezo)). The output  1424  of the decimation filter and error correction circuit  1420  represents the row force result. For the sense electrode  1406 , the amplifier  1426  receives charge from the piezoelectric layer  1408 . The common mode output range VCM_RX of the charge amplifier represents the force on the intersection  1442  of the row-column electrodes (VCM_RX=f(Qpiezo)). 
     In the illustrated embodiment, the force sensing channel  1412  is comprised of the error comparator  1438  and the decimation filter and error correction circuit  1440 . The error comparator  1438  computes a common mode correction which is the difference between the measured common mode level and the desired common mode level NCM. The error comparator  1438  can have provisions to sample the signal from the receiver AFE channel  1404  at the zero crossing of the touch signal at the common mode point (in the absence of external noise). A digital common mode correction value is then converted to an analog current by a feedback current DAC  1444 . The analog correction current is applied to the inverting input of amplifier  1426  opposite that of the piezoelectric current into amplifier  1426  to maintain the output common mode of amplifier  1426 . The feedback current DAC  1444  can be a R2R, C2C, sigma-delta DAC, or similar DAC. The common mode correction value is therefore directly related to the amount of piezoelectric current plus any parasitic currents (e.g. amplifier leakage current). The decimation filter and error correction circuit  1440  decimates the common mode correction value, and therefore the output of the decimation filter and error correction circuit  1440  is related to the force measurement. A subsequent processing block (not shown) can compensate for errors in the force measurement associated with, for example, leakage in the amplifier. In essence, the receiver AFE channel  1404 , the force processing channel  1412 , and the feedback current DAC  1444  form a sigma delta ADC, whose loop bandwidth is a function of the transconductance of the feedback current DAC  1444  and the integrator capacitor  1432 . The loop-bandwidth is adjusted to prevent saturation of the charge amplifier while providing attenuation of interferers above the loop-bandwidth of the sigma-delta ADC. The decimation filter and error correction circuit  1440  may be optimized to filter out undesired interferers above the loop-bandwidth of the sigma-delta ADC. 
       FIG. 15  is a simplified schematic diagram of a second processing channel shared by the integrated touch sensing and force sensing device. Like the  FIG. 14  embodiment, the illustrated embodiment detects force by measuring a relative charge (dQ=∝·dF). In the illustrated embodiment, the touch transmitter channel  1400  and the touch processing channel  1410  are similar to the touch transmitter channel and the touch processing channel shown in  FIG. 14 , and therefore will not be described in more detail herein. A receiver AFE channel  1500  can be connected to the sense electrode  1406 . The touch processing channel  1410  receives the output signal from the receiver AFE channel  1500 . 
     The receiver AFE channel  1500  is similar to the receiver AFE channel  1404  in  FIG. 14  with the exception of the servo/sigma delta ADC  1502 . The servo/sigma delta ADC  1502  is built around the charge amplifier  1426 . The servo/sigma delta ADC  1502  processes the touch signal from sense electrode  1406  and serves as the integrator of the sigma-delta ADC (see amplifier  1304  and feedback capacitor  1306  in  FIG. 13 ). Summing node  1302  is represented by the connection from block  1502  to the inverting input of  1426 , and ADC  1308 , flip-flop  1312 , and the feedback current DAC  1310  are included in block  1502 . 
     The servo/sigma delta ADC  1502  maintains the amplifier common mode relative to the touch stimulation signal circuit  1422 . Therefore, the output  1504  of the decimation filter and error correction circuit  1440  represents the low frequency piezoelectric and leakage charge that is directly related to the force applied to the piezoelectric layer in the integrated touch sensing and force sensing device  1408 . The bandwidth of the sigma delta ADC  1502  is sufficiently low so as to not to interfere with touch operations. The sampling rate FS of the sigma-delta ADC  1502  is selected as to be below the minimum touch stimulation signal frequency and to be correlated to the touch stimulation signal circuit  1422  to prevent noise injection into the touch processing channel  1410 . An advantage of the embodiment in  FIG. 15  is that ADC  1430  and subsequent touch processing channel  1410  need not be active for force detection, which can save power compared to the embodiment in  FIG. 14 . Furthermore, the force measurement can be used as a wake-up mechanism for touch sensing operations. For example, the circuitry related to only touch processing can be in an off or low power state. As one example, the demodulator  1434  and the accumulator  1436  in  FIG. 14  can be in an off or low power state. When a force signal equals or exceeds a given threshold value, the touch processing circuitry needed for touch processing can be activated or enabled. 
     In response to an applied force, the amplifier  1414  and the amplifier  1426  both receive charge from the piezoelectric layer in the integrated touch sensing and force sensing device  1408 . The voltage VCM_TX across the resistor  1416  represents the force on the intersection  1442  of the row-column electrodes (VCM_TX=−f(Qpiezo)). The output  1424  of the sigma delta ADC  1418  and the decimation filter and error correction circuit  1420  represents the row force result. The common mode output range VCM_RX of the amplifier  1426  represents the force on the intersection  1442  of the row-column electrodes (VCM_RX=f(Qpiezo)). The output  1504  of the servo/sigma delta ADC  1502  and the decimation filter and error correction circuit  1440  represents the column force result. 
     In some embodiments, a detected force can be used to enable a touch sensing operation.  FIG. 16  is a simplified schematic diagram of a third processing channel shared by the integrated touch sensing and force sensing device. A force is detected by measuring a relative charge (dQ=∝·dF) in the embodiment of  FIG. 16 . The voltage VCM_RX across the resistor  1416  represents the force on the intersection  1442  of the row-column electrodes (VCM_RX=f(Qpiezo)). 
     The receiver AFE channel (including amplifier  1426 , AAF  1428 , and ADC  1430 ) and the touch processing channel  1410  are similar to the receiver AFE channel and the touch processing channel shown in  FIG. 15 , and will not be described in more detail. A touch power management channel  1600  is connected to an output of the servo/sigma delta ADC  1502 . The touch power management channel  1600  receives other force results (e.g., from block  1420  and/or block  1440 ) on signal line(s)  1602 . A summing circuit  1604  sums the signals and the summed signals are received by a comparator  1606 . The output  1608  of the comparator may be used to enable a touch sensing operation. The power management channel  1600  can detect a force applied to the piezoelectric layer of the integrated touch sensing and force sensing device  1408  and use the touch detection for improved touch latency and power management. 
       FIG. 17  is a simplified schematic diagram of a fourth processing channel shared by the integrated touch sensing and force sensing device. Unlike the embodiments shown in  FIGS. 14-16 , the embodiment shown in  FIG. 17  is configured to measure the absolute charge (Q(F)=∝·(F 0 ·sin(ω MEC ·t)+F OFFSET )). In the illustrated embodiment, the touch transmitter channel  1400  and the touch processing channel  1410  are similar to the touch transmitter channel and the touch processing channel in  FIG. 14 . The receiver AFE channel  1500  is similar to the receiver AFE channel  1500  in  FIG. 15 . Therefore, these channels will not be described in more detail herein. 
     The piezoelectric layer of the integrated touch sensing and force sensing device  1408  is modulated with a force displacement signal FMEC produced by a mechanical oscillator  1700 . The amplitude of the FMEC signal modulates the force applied to the piezoelectric layer. The voltage VCM_TX across the resistor  1416  represents the force on the intersection  1442  of the row-column electrodes (VCM_RX=−f(Qpiezo)). The common mode output range VCM_RX of the amplifier  1426  represents the force on the intersection  1442  of the row-column electrodes (VCM_RX=f(Qpiezo)). 
     A separate demodulator channel  1702  demodulates the amplitude modulated charge from the piezoelectric layer in the integrated touch sensing and force sensing device  1408 . The output  1704  of the integrator  1706  represents the charge or force on the sense electrode  1406 . The output from the sigma delta converter  1418  in the touch transmitter channel  1400  is processed by the demodulator  1708  and the integrator  1710 , and the output  1712  represents the charge or force on the drive electrode  1402 . 
     The embodiment shown in  FIG. 17  may also be used to provide tactile or haptic feedback. The mechanical oscillator  1700  can be amplitude modulated based on the user input applied to the integrated touch sensing and force sensing device. For example, pressing a button on an on-screen keyboard may be used to modulate the amplitude of the mechanical oscillator  1700  to produce haptic feedback. 
     In the embodiments shown in  FIGS. 14-17 , the output that represents the force on the drive electrode  1402  and the output that represents the force on the sense electrode  1406  can be processed by a processing device (e.g., processing device  300 ) to correlate the output signal to a value that represents the force. Similarly, the outputs from the touch processing channels that represent the touch may be processed by a processing device. 
     Referring now to  FIG. 18 , a flowchart of a method of power management in an integrated touch sensing and force sensing device is shown. Initially, some or all of the circuitry associated only with processing touch inputs may be in an off or low power state (block  1800 ). As described earlier, the demodulator  1434  and the accumulator  1436  in  FIG. 14  can be in an off or low power state at block  1800 . A force input is then received and processed by the receiver AFE channel at block  1802 . Next, as shown in block  1804 , a determination can be made as to whether or not the force signal equals or exceeds a given threshold value. If not, the process returns to block  1802 . If the force signal equals or exceeds the given threshold value, the method passes to block  1806  where the circuitry associated with processing touch inputs is enabled and the touch input or inputs associated with the force input is processed by the receiver AFE channel and the touch processing channel. A determination may then be made at block  1808  as to whether or not processing of the touch input(s) is complete. If not, the process waits at block  1808 . If processing of the touch input(s) is complete, the method returns to block  1800 . 
     When the electrodes  406  and  408  are configured as shown in  FIGS. 9 and 10 , force inputs can be acquired using projection scanning, where force inputs are acquired on M columns and N rows. Superimposing the row and column results yields M×N results. However, phantom touch inputs may occur if more than one touch input is applied to the integrated touch sensing and force sensing device. For example, if an integrated touch sensing and force sensing device with four rows (enumerated rows  0  to  3 ) and four columns (enumerated columns  0  to  3 ) is used and touch inputs are applied at locations ( 1 , 1 ) and ( 2 , 2 ), phantom images may be induced at locations ( 1 , 2 ) and ( 2 , 1 ) and the location of the force inputs cannot be resolved. However, the location of the touch inputs can be resolved by using the touch signals. Therefore during processing, force inputs can be related to touch signals. 
       FIG. 19  is a simplified schematic diagram of a fifth processing channel shared by the integrated touch sensing and force sensing device. The  FIG. 19  embodiment employs self-capacitance measurement rather than mutual capacitance measurement used in the embodiments shown in  FIGS. 14-17 . In the embodiment shown in  FIG. 19 , a stimulation signal circuit V STIM  is applied to the non-inverting input of the amplifier  1426 , and the output of amplifier  1426  is a function of the capacitance of the integrated touch sensing and force sensing device  1100  and the feedback capacitance as follows: Vout=V STIM *(1+Cpiezo/Cf), where V STIM  is the amplitude of the stimulation signal, Cf is the feedback capacitance, Cpiezo is the capacitance of the integrated touch sensing and force sensing device  1100  including any capacitance imposed on the integrated touch sensing and force sensing device  1100  due to the proximity of a finger. The phase sensitive demodulation of the touch signal in block  1410  occurs at the same frequency as the frequency of the stimulation signal circuit V STIM . The operation of the force processing channel is the same as that described in conjunction with the embodiments of  FIGS. 14-17 . 
     The decimation and error correction block  1440  performs error correction on the force signals. Errors can be induced, for example, by non-linearities in the force processing channel, interferers (internal and external), parasitic effects, such as leakage currents induced by the amplifier  1426 , or sensor effects, such as temperature induced sensor deformation. Example error correction techniques may include adaptive offset compensation, base-lining, and adaptive filtering as a function of parameters such as temperature. 
     Although  FIGS. 14-17 and 19  depict a single receiver AFE channel, a single touch processing channel, a single force processing channel, a single power management channel, and a single demodulator channel, those skilled in the art will recognize that the integrated touch sensing and force sensing device can be operably connected to multiple processing channels. As one example, each intersection of a row electrode and a column electrode (see  FIGS. 9 and 10 ) can be operably connected to a receiver AFE channel, a touch processing channel, and a force processing channel. In other words, multiples of the processing channels shown in  FIGS. 14-17  and  FIG. 19  may be operably connected to each intersection of a row electrode and a column electrode. 
     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. 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: 20170619
Publication Date: 20181211
Grant Date: 20181211
Priority Date: 20140926
Inventors: KRAH, CHRISTOPH H.
Assignee: APPLE INC
CPC Classifications: [{"code": "G06F2203/04105", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/044", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/0418", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0412", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0414", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/016", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F2203/04106", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/04182", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0446", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0445", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0412", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/04182", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0446", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F2203/04106", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F2203/04106", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/0445", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0412", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F2203/04105", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/016", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/016", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F2203/04105", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 59069608