Abstract:
A system includes an electromechanical device coupled to a sensing device to detect input to the electromechanical device and display to displays information related to the electromechanical device. The sensing device includes a touch surface including tactile features delineating a portion of the touch surface to be touched by the conductive object. A sensor of the system is to detect the conductive object proximate to the delineated portion of the touch surface based on a capacitance.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 13/247,248, filed Sep. 28, 2011, which is incorporated by reference herein in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present disclosure related generally to proximity and/or touch sensing systems, and more particularly to capacitance proximity/touch sensing systems and methods. 
       BACKGROUND 
       [0003]      FIG. 15  shows a conventional capacitance sensing system  1500  that includes sense electrodes (one shown as  1502 ), grounded electrodes (two shown as  1504 - 0 / 1 ), and a capacitance sensing circuit  1506 . In the absence of a sense object  1508  (e.g., part of a body such as a finger, a stylus, or other conductive object) a capacitance Cp exists between the sense electrode  1502  and ground. The presence of a sense object  1508  introduces a capacitance Cf. 
         [0004]    Schematic  1510  shows a capacitance Cx sensed by capacitance sense circuit  1506 . Cf varies according to the proximity of a sense object  1508 . In particular, Cx will grow bigger in the presence of a sense object  1508 . 
         [0005]    Conventional system  1500  includes a nonconductive touch surface  1512  serving as a touch surface. Non-conductive touch surface  1512  prevents sense objects (e.g.,  1508 ) from touching a sense electrode (e.g.,  1502 ). Absent such a nonconductive touch surface  1512 , when a sense object  1508  makes direct contact with sense electrode  1508 , because it is a conductor to ground, it can increase a capacitance between all other sense electrodes and ground, erroneously triggering touch indications for all other sense electrodes. 
         [0006]    The above limitation has prevented capacitance sensing on a contiguous conductive surface. 
         [0007]    Other conventional sensing systems have utilized sense methods other than capacitance sensing in combination with a conductive sense surface. As a first example, conventional systems have utilized piezoelectric sensors in contact with a conductive surface. In response to strain induced by touch events, piezoelectric sensors can generate an electric field. Drawbacks to piezoelectric sensors can include difficulty in tuning responses to customer&#39;s liking, susceptibility to radio frequency (RF) noise/interference (e.g., 800 MHz, 1.9 GHz signals can interfere with sense results), and cost of components, as piezoelectric systems can require higher precision analog-to-digital converters. 
         [0008]    As a second example, mechanical buttons can include conductive surfaces. Drawbacks to mechanical buttons can be susceptibility to wear and tear from moving/contacting parts and dust/debris. Other drawbacks include the expense in making mechanical buttons waterproof or resistant. Further, for many applications, mechanical buttons can lack the aesthetics for a given design. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIGS. 1A to 1C  are diagrams showing capacitance sensing systems having a conductive touch surface according to embodiments. 
           [0010]      FIG. 2  is a diagram showing a capacitance sensing system having a multi-layer conductive touch surface according to an embodiment. 
           [0011]      FIGS. 3A to 3E  are cross sectional views showing embodiments having variations between a sense electrode dimension and corresponding compressible region formed above the sense electrode, as well as shape of a conductive touch surface. 
           [0012]      FIGS. 4A to 4D  are diagrams showing capacitance sensing systems having a conductive touch surface that can also serve as a proximity sensing electrode, according to embodiments. 
           [0013]      FIG. 5  is a schematic diagram of a capacitance sensing system that can provide proximity and “button” type sensing according to one embodiment. 
           [0014]      FIGS. 6A to 6C  are diagrams showing parts of a sense assembly according to an embodiment. 
           [0015]      FIGS. 7A to 7D  are tables showing sensing results of conventional capacitance sensing systems. 
           [0016]      FIGS. 8A and 8B  show a conventional capacitance sensing system with a nonconductive touch surface. 
           [0017]      FIGS. 9A and 9B  show a capacitance sensing system according to one embodiment that can be substituted for that shown in  FIG. 8A , 
           [0018]      FIG. 10  shows a consumer electronic system according to one embodiment. 
           [0019]      FIG. 11  shows a consumer appliance system according to another embodiment. 
           [0020]      FIGS. 12A and 12B  are diagrams showing an input system according to a further embodiment. 
           [0021]      FIG. 13  is a flow diagram of a method according to an embodiment. 
           [0022]      FIG. 14  is a flow diagram of a method according to another embodiment. 
           [0023]      FIG. 15  is a block schematic diagram of a conventional capacitance sensing system. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    Various embodiments will now be described that show capacitance sensing circuits, systems and methods that can utilize a conductive touch surface enabling capacitance sensing applications and capabilities beyond those achieved with conventional approaches requiring a nonconductive touch surface. 
         [0025]    In the various embodiments shown below, like section are referred to by the same reference character but with the first digit(s) corresponding to the figure number. 
         [0026]      FIGS. 1A and 1B  show a capacitance sensing system  100  according to an embodiment. A system  100  can include a conductive touch surface  102 , one or more sense electrodes (one shown as  104 ), a nonconductive structure  106  formed between the touch surface  102  and sense electrodes (e.g.,  102 ), and a capacitance sense circuit  108 . 
         [0027]    A conductive touch surface  102  can be formed from one or more layers, one layer being formed from a conductive material for contact with a sense object (i.e., an object that contacts the touch surface to indicate an input event). This is in sharp contrast to a conventional system like that of  FIG. 15  that may include a nonconductive touch surface  1512 . A conductive touch surface  102  can be formed by any suitable conductive material, and in particular embodiments can include one or more metallic layers. Such a metallic layer can be composed of one metal, or may be an alloy. In some embodiments, a conductive touch surface  102  can be a contiguous structure formed over multiple sense electrodes (e.g.,  104 ). However, in alternate embodiments a conductive touch surface  102  can be non-contiguous, having openings formed therein. 
         [0028]    Sense electrodes (e.g.,  104 ) can be formed below a touch surface  102  and can be physically separated from a touch surface  102  by a distance. As will be described below, in particular embodiments, such a distance can vary in response to a sense object (e.g.,  110 ) contacting touch surface  102 . When a sense object (e.g.,  110 ) contacts a touch surface  102  over a sense electrode, the sense electrode can exhibit a change in capacitance. Thus, in some embodiments, each of sense electrodes (e.g.,  104 ) can serve as a “button” that senses contact with the portion of the touch surface  102  above it. 
         [0029]    Sense electrodes (e.g.,  104 ) can be formed from any suitable conductive material. In some embodiments, sense electrodes (e.g.,  104 ) can be substantially coplanar with one another. In addition or alternatively, sense electrodes (e.g.,  104 ) can be parallel to touch surface  102 . In  FIGS. 1A and 1B , sense electrodes (e.g.,  104 ) can be formed on a substrate  114 . In a very particular embodiment, sense electrodes (e.g.,  104 ) can be conductive regions formed on a printed circuit board (PCB), and substrate  114  can be a PCB with conductive layers formed therein to connect each sense electrode ((e.g.,  104 ) to a capacitance sense circuit  108 . 
         [0030]    A nonconductive structure  106  can include first portions  106 - 0  and second portions  106 - 1 . First portions  106 - 0  can be formed between each sense electrode (e.g.,  104 ) and conductive touch surface  102  in a direction perpendicular to the touch surface  102 . Second portions  106 - 1  can be formed between first portions  106 - 0  in a direction parallel to a touch surface  102 . First portions  106 - 0  can be more compressible than second portions  106 - 1 . In one embodiment, when a sense object (e.g.,  110 ) presses down on a touch surface  102 , a first portion  106 - 0  below the touch location can compress more than second portions  106 - 1 , decreasing a distance between the corresponding sense electrode (e.g.,  104 ) and touch surface  102 , and thus increasing a capacitance. 
         [0031]    In some embodiments, a nonconductive structure  106  can be a rigid, nonconductive layer positioned over sense electrodes (e.g.,  104 ), and first portions  106 - 0  can be openings formed within such an overlay. Second portions  106 - 2  can be solid regions between such openings. In a very particular embodiment, a nonconductive structure  106  can be a polymer having openings formed therein, even more particularly an acrylic resin. In other embodiments, a nonconductive structure  106  can include a glass or any other suitable nonconductive material. 
         [0032]    A capacitance sensing circuit  108  can be any suitable capacitance sensing circuit for detecting changes in a capacitance with respect to at least each sense electrode (e.g.,  104 ). As shown in  FIG. 1A , suitable capacitance sensing circuits include, but are not limited to: sigma-delta modulating (CSD) capacitance sense circuit  112 - 0 , a successive approximation register (CSA) capacitance sense circuit  112 - 1 , or an integrating type capacitance sense circuit  112 - 2 . 
         [0033]      FIG. 1A  shows a system  100  prior to a touch event. Absent a sense object  110  there can be an initial distance (d 1 ) between a sense electrode (e.g.,  104 ) and touch surface  102 . In a particular embodiment, a touch surface  102  can be connected to ground and a capacitance (Cinit) measured by capacitance sense circuit  108  can be given by the well-understood relationship Cinit=ε*(A/d 1 ) where εis permittivity of a dielectric between sense electrode  104  and touch surface  102 , and A is an area of parallel plates presented by sense electrode  104  and the corresponding portion of touch surface  102 . 
         [0034]      FIG. 1B  shows a system  100  during a touch event. A touch surface  102  can be connected to ground. A sense object  110  can contact touch surface  102  and cause a distance between sense electrode (e.g.,  104 ) and touch surface  102  to decrease from d 1  to d 2 . Consequently, a capacitance measured by capacitance sense circuit  108  can be Ctouch=ε*(A/d 2 ) where d 2 &lt;d 1 . 
         [0035]    While  FIGS. 1A and 1B  have shown a system that can employ a self-capacitance sensing, alternate embodiments can utilize mutual capacitance sensing.  FIG. 1C  shows one example of such an embodiment. 
         [0036]      FIG. 1C  shows a system  100 ′ having items like those of  FIG. 1A . However, unlike  FIG. 1A , in  FIG. 1C  a conductive touch surface  102  can be driven with a transmit signal TX. A mutual capacitance (Cm) between the conductive touch surface  102  and sense electrode (e.g.,  104 ) can increase when an object presses on the conductive touch surface  102 , decreasing a distance between the two. 
         [0037]    In this way, touches on a conductive surface can be capacitively sensed. 
         [0038]      FIG. 2  shows a capacitance sensing system  200  according to another embodiment. A system  200  can include items like those of  FIGS. 1A and 1B , and such items can be subject to the same variations as noted for the embodiment of  FIGS. 1A / 1 B. 
         [0039]      FIG. 2  differs from  FIGS. 1A and 1B  in that a conductive touch surface  202  can include multiple layers  202 - 0 ,  202 - 1 . A top layer  202 - 0  (i.e., layer that is touched) can be a conductive layer, while one or more lower layers (e.g.,  202 - 1 ) can be nonconductive or conductive. In one particular embodiment, a top layer  202 - 0  can be a conductive paint, while a lower layer  202 - 1  can be a flexible sheet, such as plastic, as but one example. 
         [0040]    Embodiments above have shown systems in which a compressible region (e.g., an opening) can have a same width as a corresponding sense electrode (where width is determined in a direction parallel to a touch surface  302 ). However, other embodiments can include variations in size between compressible portions corresponding sense electrodes. 
         [0041]      FIGS. 3A and 3B  show sense systems  300 -A/B having features like those of  FIGS. 1A and 2 .  FIG. 3A  differs from the above embodiments in that a width of a compressible portion  306 - 0 A (Wp) can be greater than a width (Ws) of a corresponding sense electrode  304 -A. Thus, a compressible portion (e.g., an opening) can extend beyond some or all of the edges of the corresponding sense electrode. 
         [0042]      FIG. 3B  differs from the above embodiments in that a width of a compressible portion  306 - 0 B (Wp) can be less than a width (Ws) of a corresponding sense electrode  304 -B. Thus, a sense electrode can extend beyond some or all of the edges of the corresponding compressible portion. 
         [0043]    While embodiments shown herein include touch surfaces that are flat, alternate embodiments can include touch surfaces with various other surface forms.  FIGS. 3C  to  3 E show three examples of variations in touch surface shape.  FIGS. 3C to 3E  shows how touch surfaces  302 C,  302 D and  302 E can have portions that rise above and/or fall below other portions of the same surface. Such features can provide a tactile indication of where a sense electrode is located (and hence where the surface can be touched) and/or a mechanical spring effect. 
         [0044]    It is understood that  FIGS. 3C to 3E  are but a few of many possible alternate embodiments. 
         [0045]    Embodiments above shown capacitance sense systems having a conductive touch surface with sense electrodes formed below. Alternate embodiments can advantageously utilize a conductive touch surface as a capacitance based proximity sense electrode. In such embodiments, a system can switch between a proximity sensing mode and a touch sensing mode. Particular embodiments having such capabilities will now be described. 
         [0046]      FIGS. 4A and 4B  show a system  400  having sections like those of  FIGS. 1A /B.  FIGS. 4A /B differ from  FIGS. 1A /B in that a capacitance sense circuit  408  can include touch sense circuits  416 , proximity sense circuits  418 , a controller  420 , and a mode switch  422 . Touch sense circuits  416  can detect changes in capacitance between a sense electrode  404  and conductive touch surface  402 . Proximity sense circuits  418  can sense capacitance changes with respect to touch surface  402  (e.g., capacitance between touch surface  402  and ground). It is understood that touch sense and proximity sense circuits ( 416  and  418 ) can include the same circuit components, share some circuit components, or can be separate circuits. 
         [0047]    A controller  420  can control sense operations of capacitance sensing circuit  408 , including operations of mode switch  422 . As will be described in more detail below, a controller  420  can switch system  400  between different operations. 
         [0048]    A mode switch  422  can selectively switch a touch surface  402  between different nodes depending upon a mode of operation. In the particular embodiment shown, a switch circuit  422  can include a multiplexer that switches a touch surface  402  between a proximity sense circuit  418  and a ground node  424 . 
         [0049]      FIG. 4A  shows a system configured for a first mode of operation. In response to a mode signal from controller  420 , a mode switch  422  can connect conductive touch surface  402  to proximity sense circuits  418 . Touch sense circuits  416  can be deactivated. In a first mode, a capacitance of touch surface  402  can be sensed by proximity sense circuit  418  to detect when a proximity sense object  410 ′ approaches the touch surface  402 . In one embodiment, upon detecting the proximity of sense object  410 ′ a controller can switch to a second mode of operation. 
         [0050]      FIG. 4B  shows a system configured for a second mode of operation. In response to a mode signal from controller  420 , a mode switch  422  can connect conductive touch surface  402  to ground node  424 . In addition, touch sense circuits  416  can be activated, while proximity sense circuits  418  can be deactivated. In a second mode, a capacitance of sense electrodes (e.g.,  404 ) can be sensed to determine if a touch has occurred on touch surface  402  above such sense electrodes. 
         [0051]      FIGS. 4C and 4D  show a system  400 ′ having sections like those of  FIGS. 4A /B.  FIGS. 4C /D differ from  FIGS. 4A /B in that a mode switch  422  can connect touch surface  402  to a transmit signal driver circuit  409  in a second mode of operation. Touch sense circuits  416  can then employ mutual capacitance sensing to detect a touch above a sense electrode (e.g.,  404 ). 
         [0052]    In this way, a capacitance sense system can utilize a conductive surface for proximity sensing in one mode, and as a conductive capacitance sensing touch surface in another mode. 
         [0053]      FIG. 5  shows a capacitance sensing system  500  according to another embodiment. In a very particular arrangement, system  500  can be one particular implementation of that shown in  FIGS. 4A /B. 
         [0054]    A system  500  can include a conductive touch surface  502 , sense electrodes  504 - 0  to - 5  formed below the touch surface  502 , and a capacitance sense circuit  508 . A capacitance sense circuit  508  can include a mode switch circuit  522 , a sigma-delta modulation (CSD) circuit  512 - 0 , a controller  520 . and components  526 . A mode switch circuit  522  can include a touch surface MUX  522 - 0  and an electrode MUX  522 - 1 . A touch surface MUX  522 - 0  can switch a touch surface  502  between a sense node  528  and a ground node  524  in response to a mode signal MODE. An electrode MUX  522 - 1  can connect any of sense electrodes ( 504 - 0  to - 5 ) to sense node  528  in response to a select signal SEL. 
         [0055]    A CSD circuit  512 - 0  can detect capacitance changes at a sense node  528 . In the particular embodiment shown, a CSD circuit  512 - 0  can include charge switch  530 - 0 , sample switch  530 - 1 , discharge switch  530 - 2 , a comparator  532 , a latch  534 , an oscillator circuit  536 , a pseudorandom sequence generator  538 , gate  540 , analog-to-digital converter/pulse width modulator (ADCPWM)  542 , and timer  544 . According to known sigma-delta modulating capacitance sense techniques, switches  530 - 0  to - 1  can form a switched capacitor circuit that charges modulating capacitor (Cmod). Modulating capacitor (Cmod) disharges through bleed resistor RB. Pulses generated by comparator  532  can be converted into count values (CNT) by timer  544 . Such count values can be provided as sensed capacitance values to controller  520 . 
         [0056]    Components  526  can include passive circuit components selected for an expected capacitance to be sensed, a desired response speed, and/or touch sensitivity. In the embodiment shown, components can include a modulating capacitor Cmod and a bleed resistor RB. 
         [0057]    A controller  520  can store, and/or have access to, threshold values for determining a sense event. In the particular embodiment shown, a controller  520  can include storage locations  546 - 0  for storing one or more proximity threshold values and storage locations  546 - 1  for storing one or more button threshold values corresponding to each sense electrode. A controller  520  can also include comparator circuits (represented by  548 ) for comparing threshold values in storage locations ( 546 - 0 ,  546 - 1 ) to count values (CNT) output from timer  544 . 
         [0058]    In a very particular embodiment, a controller  520  can include a processor that executes stored instructions. In such an embodiment, a comparator  548  can be formed by an arithmetic logic unit (ALU) of the processor. However, in alternate embodiments, all or portions of a controller  520  can be formed by custom circuits and/or programmable circuits. 
         [0059]    Having described various sections of a system  500 , two modes of operation for the system will now be described. 
         [0060]    In a first mode of operation, a system  500  can operate in a proximity sensing mode, determining if a conducting object is in proximity to a touch surface  502 . In a first mode, a controller  520  can generate mode signals (MODE) that cause touch surface MUX  522 - 0  to connect touch surface  502  to sense node  528 , and select signals SEL that disconnect sense electrodes ( 504 - 0  to - 5 ) from sense node  528 . CSD circuit  512 - 0  can begin generating count values (CNT) based a sensed capacitance Cx between sense node  528  and a ground node  524 . A controller  520  can compare count values (CNT) to proximity threshold values in storage locations  546 - 0 . If count values exceed a proximity threshold value, a controller  520  can determine a proximity sense object ( 510 ′) is within proximity of touch surface  502 . In particular embodiments, upon detecting the proximity of an object, a system  500  can switch to a second mode. 
         [0061]    In a second mode of operation, a system  500  can sense if touches occur on touch surface  502  above any of the sense electrodes ( 504 - 0  to - 5 ), enabling regions above the sense electrodes ( 504 - 0  to - 5 ) to operate as touch “buttons”. A controller  520  can generate mode signals (MODE) that cause touch surface MUX  522 - 0  to connect touch surface  502  to ground node  524 . In addition, controller  520  can generate select signals SEL that can sequentially connect each sense electrode ( 504 - 0  to - 5 ) to sense node  528 . CSD circuit  512 - 0  can generate count values (CNT) based a sensed capacitance Cx, which can represent a capacitance change between a sense electrode ( 504 - 0  to - 5 ) and touch surface  502 . A controller  520  can compare count values (CNT) for each sense electrode ( 504 - 0  to - 5 ) (i.e., button) to a corresponding button threshold value in storage locations  546 - 1 . If count values exceed a button threshold value, a controller  520  can determine that a touch has occurred above the corresponding sense electrode ( 504 - 0  to - 5 ). 
         [0062]    It is understood that a controller can include various additional processes that operate on count values (CNT) before and/or after comparison to threshold values. 
         [0063]    Such additional processes include, but are not limited to, filtering and/or hysteresis with respect to count values and threshold limits. 
         [0064]    While a system  500  can be implemented with various circuit types, in one very particular embodiment, a capacitance sense circuit  508  can be formed with a programmable system on chips device, such as the PSoC®3 and/or PSoC®5 device manufactured by Cypress Semiconductor Corporation of San Jose, Calif., U.S.A. 
         [0065]      FIGS. 6A to 6C  show components of a sense assembly that can be included in embodiments.  FIG. 6A  shows a bottom section  650 . A bottom section  650  can be a PCB having sense electrodes (one shown as  604 ) patterned thereon. In the particular embodiment shown, sense electrodes (e.g.,  604 ) are circular shaped in a four-by-four array. However, sense electrodes can have any suitable shape according to a desired application. Sense electrodes (e.g.,  604 ) can have conductive connections to corresponding leads  652 . Leads  652  can be connected to a capacitance sense circuit (not shown). 
         [0066]      FIG. 6B  shows a nonconductive structure  606  that can be attached to be situated over bottom section  650 . In the particular embodiment shown, nonconductive structure  606  can be single, relatively rigid sheet with openings (one shown as  606 - 0 ) formed therein. Openings  606 - 0  can form compressible regions with respect to a touch surface (not shown). Areas between openings (shown as  606 - 1 ) can form less, or non-compressible regions. In the particular embodiment shown, openings (e.g.,  606 - 0 ) can have a same size as, and can be vertically aligned with, sense electrodes (e.g.,  604 ) of bottom section  604 . However, as understood with reference to  FIGS. 3A / 3 B, openings (e.g.,  606 - 0 ) can have dimensions different than those of their corresponding sense electrodes. A nonconductive structure  606  can be made from any suitable nonconductive material, including those noted for item  106  in  FIGS. 1A / 1 B, or equivalent materials. A nonconductive structure  606  can be physically attached to bottom structure  650 . 
         [0067]      FIG. 6C  shows a conductive touch surface  602  according to an embodiment. A touch surface  602  can be an integral conductive structure attached to nonconductive structure  606 . In a particular embodiment, a touch surface  602  can have a uniform thickness, and can be a metallic sheet, as but one example. 
         [0068]    It is understood that  FIGS. 6A to 6C  show but one very particular embodiment, and should not be construe as limiting. 
         [0069]      FIGS. 7A to 7D  are tables showing experimental results for conventional sensing systems. Each of the tables includes the following columns: BUTTON DIAM., which shows a diameter of a sense electrode in millimeters (mm); AIR GAP shows a distance between a touch surface and a sense electrode (i.e., vertical depth of an opening) absent an object touching a touch surface in mm; RAW CNTS shows a number of raw counts (background counts) generated by a CSD type capacitance sense circuits; DIFF CNTS can be a change in counts resulting from an object touching a touch surface above a sense electrode; NOISE can be counts attributed to noise in RAW CNTS; and SNR can be a resulting signal-to-noise ratio of the system. 
         [0070]      FIG. 7A  shows results for a conventional arrangement in which a non-conductive touch surface has a 1 mm thickness. Further, a hole diameter (e.g., compressible portion of a nonconductive structure) matches that of the sense electrodes (i.e., the button diameter). 
         [0071]      FIG. 7B  shows results for a conventional arrangement in which a non-conductive touch surface has a 2 mm thickness and hole diameters match sense electrode diameters. 
         [0072]      FIG. 7C  shows results for a conventional arrangement in which a non-conductive touch surface has a 1 mm thickness and hole diameters are greater than sense electrode diameters. 
         [0073]      FIG. 7D  shows results for a conventional arrangement in which a non-conductive touch surface has a 2 mm thickness and hole diameters are greater than sense electrode diameters. 
         [0074]    It is expected that embodiments described herein can be used to replace or improve existing conventional piezoelectric, mechanical button and/or capacitance sensing systems. In the latter case, conventional sense electrode structures can be used in combination with a newly added conductive touch surface to improve a function of, or aesthetics in, an application.  FIGS. 8A to 8D  show an example of such a case. 
         [0075]      FIGS. 8A and 8B  show a conventional capacitance sensing input structure  801  for an electronic device, such as a monitor or television, for example. Input structure  801  can include a PCB  850  and a nonconductive touch surface  803 . Sense electrodes (S 0  to S 5 ) (one shown as  804 ) can be patterned layers on a surface of PCB  850 . In a particular embodiment, a nonconductive touch surface  803  can be a plastic layer. Sense electrodes  804  can have conductive connections to leads  852  through PCB  850 . 
         [0076]    In one implementation, a PCB  850  can have a thickness (tb) of about 1 mm and a nonconductive touch surface  803  can have a thickness (tn) of about 1.6 mm. 
         [0077]    When a sense object  810  is in proximity with a sense electrode  804 , it can induce a change in capacitance with respect to the sense electrode. 
         [0078]      FIG. 8B  it&#39;s a table showing sense results for the conventional structure of  FIG. 8A . The table of  FIG. 8B  includes the following columns: SENSOR, which identifies the sensor; NOISE can be counts attributed to noise; Raw Counts, can shows a number of raw counts generated by a CSD type capacitance sense circuit; Cp can be a capacitance sensed by a system (in picoFarads), SNR can be a resulting signal-to-noise ratio of the system.  FIG. 8B  shows count values and capacitance values when no finger is present over a sense electrode (No Finger Presence), and when a finger is present over a sense electrode (Finger Presence). 
         [0079]      FIGS. 9A and 9B  show a capacitance sensing input structure  956  according to an embodiment. In a particular embodiment, input structure  956  can serve as a substitute for that shown in  FIG. 8A . Input structure  956  can include a PCB  950 , a nonconductive structure  906 , and a conductive touch surface  902 . As in the case of  FIG. 8A , sense electrodes (S 0  to S 5 ) (one shown as  904 ) can be patterned layers on a surface of PCB  950  having conductive connections to leads  952 . A nonconductive structure  906  can be a plastic layer having compressible portions (one shown as  906 - 0 ) and less compressible portions (one shown as  906 - 1 ). In one embodiment, a nonconductive structure  906  can be a plastic layer and compressible portions  906 - 0  can be openings formed in the plastic layer. In one embodiment, a PCB  950  can be substantially the same as that utilized in a conventional capacitance sensing system  801 . 
         [0080]    In one implementation, a PCB  950  can have a thickness (tb) of about 1 mm and a nonconductive structure  906  can have a thickness (tn) of about 1.2 mm, and a conductive touch surface  902  can have a thickness (ts) of about 0.2 mm. Accordingly, embodiment  956  can have a form factor suitable for replacing that of  FIG. 8A . 
         [0081]    When a sense object  910  contacts (e.g., a gentle press) a touch surface  902  over a sense electrode (S 0  to S 5 ), a change in capacitance between the sense electrode and touch plate can occur, indicating a touch event. 
         [0082]      FIG. 9B  it&#39;s a table showing sense results for the embodiment of  FIG. 9A . The table of  FIG. 9A  includes the same columns as those of  FIG. 8B . 
         [0083]    In a particular embodiment, a capacitance sensing input structure  956  can include backlighting that can illuminate a touch surface  902  from behind. In one very particular embodiment a light source  951  can be positioned behind a PCB and provide light (e.g.,  953 ) to a back of PCB  950 . A PCB  950  and/or touch surface  902  can have openings that enable light to shine through. 
         [0084]    In this way, a sensing system having a conductive touch surface can be used in applications having conventional capacitance sensing with a nonconductive touch surface. 
         [0085]    Embodiments of the invention can include various electrical and/or electromechanical devices employing capacitive sensing with a conductive touch surface as described herein, equivalents. As but a few examples, systems according to embodiments described herein can include electronics products, automation products, appliances (e.g., “white” goods), as well as automotive, aeronautic and/or nautical devices. Particular examples of such embodiments will now be described. The below embodiments can utilize touch sensing based on a capacitance changes between a conductive touch surface and sense electrodes as described herein, or equivalents. 
         [0086]    Further, such embodiments can also include proximity sensing in combination with such touch sensing, in which a conductive touch surface is utilized as a proximity sensing electrode. 
         [0087]      FIG. 10  shows a system  1058  according to a particular embodiment. A system  1058  can be a display device having a conductive touch surface  1006  formed thereon. A touch surface  1006  can form part of a sensing system  1000  (shown in a cross section) like that shown in embodiments above. In a particular embodiment, a touch surface  1006  can be a portion of a larger contiguous metallic surface, for a desirable aesthetic. Such a contiguous surface can also enable high resistance to moisture for easy cleaning. 
         [0088]      FIG. 11  shows another system  1158  according to an embodiment. A system  1158  can be a household appliance. As in the case of  FIG. 10 , an appliance can include a conductive touch surface  1106  to control the system  1158 . In a particular embodiment, a touch surface  1106  can be a portion of a larger contiguous metallic surface for advantages noted in the embodiment of  FIG. 10 . 
         [0089]      FIGS. 12A and 12B  show another system  1258  according to an embodiment. A system  1258  can be a touch interface for a device, such as an automatic teller machine (ATM), as but one embodiment.  FIG. 12A  shows a top plan view of a touch surface  1206 .  FIG. 12B  shows a side cross sectional view through a portion of the touch interface, shown by line B-B in  FIG. 12A . 
         [0090]      FIGS. 12A /B show how a system  1258  can include tactile features (one shown as  1260 ) on a touch surface  1206  to delineate touch locations. In this way, “buttons” can be designated regions of a contiguous conductive structure, and not mechanical buttons integrated into a surface. Tactile features (e.g.,  1206 ) can delineate “button” center locations, button perimeters, or both. 
         [0091]      FIG. 12B  shows items like those of  FIG. 1A , and such items can be formed of the same or equivalent structures as  FIG. 1A . In addition,  FIG. 12B  shows how tactile structures (e.g.,  1260 ) can identify touch locations (e.g., “buttons”) on a contiguous touch surface  1202 . 
         [0092]    While embodiments above have shown systems, circuits, and associated methods, additional method embodiments will now be described with reference to a number of flow diagrams. 
         [0093]      FIG. 13  shows a method  1370  according to one embodiment. A method  1370  can include monitoring a capacitance between a conductive touch surface and one of multiple sense electrodes formed below the touch surface ( 1372 ). In a particular embodiment, such an action can include connecting a touch surface to ground, and sensing a capacitance between each sense electrode and ground. Further, such sensing can include any suitable capacitance sensing method. In a particular embodiment, such capacitance sensing can include sigma-delta modulation capacitance sensing as described herein, or an equivalent capacitance sensing approach. 
         [0094]    If a sensed capacitance is greater than a minimum capacitance change (ΔC_touch) required to indicate a touch (Y from  1374 ), a touch can be indicated ( 1376 ). Such an action can include indicating a touch event for the particular electrode to enable an electrode to operate as a “button”. After indicating a touch, a method  1370  can proceed to  1378 . If a sensed capacitance is not outside of a range (N from  1374 ), a method  1370  can determine if a last sense electrode has been reached  1378 . 
         [0095]    If a last sense electrode has not been reached (N from  1378 ), a method  1370  can go to a next sense electrode  1382 , and then return to  1372 . If a last sense electrode is reached (Y from  1378 ), a method  1370  can go to a first sense electrode  1382 , and then return to  1372 . 
         [0096]      FIG. 14  shows a method  1470  according to another embodiment. A method  1470  can include setting a mode to a proximity sensing mode ( 1482 ). A conductive touch surface can be connected to a capacitive sense circuit ( 1484 ). A capacitance between a touch surface and ground (Cs) can be sensed ( 1486 ). Such an action can include any of the sensing methods noted for embodiments herein, or equivalents. If a sensed capacitance is not greater than a minimum capacitance change (ΔC_prox) (N from  1488 ), a method  1470  can return to  1486  and proximity sensing with a touch surface can continue. A minimum capacitance change (ΔC_prox) can be a value for determining if an object is within a proximity of a touch surface. Such a value can vary according to operating environment and/or application. 
         [0097]    If a sensed capacitance is greater than a minimum capacitance change (ΔC_prox) (Y from  1488 ), a method  1470  can switch to a touch sense mode ( 1490 ). A conductive touch surface can be connected to a ground ( 1494 ). Initial values for sensing capacitance for multiple electrodes can be set. In the embodiment shown, this can include setting an electrode selection value (i) to zero, and starting a time out counter ( 1492 ). 
         [0098]    A selected sense electrode can be connected to a capacitance sense circuit ( 1496 ). A capacitance between a touch surface and a selected electrode can be sensed ( 1498 ). Such an action can include any of the sensing methods noted for embodiments herein, or equivalents. If a sensed capacitance is greater than a minimum capacitance (ΔC_touch) (Y from  1499 ), a method  1470  can determine that a touch has occurred at a “button” corresponding to the selected electrode, and a timer can be reset ( 1497 ). Such a touch indication can be provided to other portions of a system as input events, for example. 
         [0099]    If a sensed capacitance is not greater than a minimum capacitance (ΔC_touch) (N from  1499 ), a method  1470  can check if a last sense electrode has been reached (i=imax) ( 1495 ). If a last sense electrode has not been reached (N from  1495 ), a next sense electrode can be selected ( 1493 ). If a last sense electrode has been reached (Y from  1495 ), a method  1470  can check if a timer has reached a timeout limit ( 1491 ). If a timeout limit has not been reached (N from  1491 ), a method  1470  can return to  1492  to repeat a scanning of the sense electrodes. If a timeout limit has been reached (Y from  1491 ), a method  1470  can return to  1482  and enter the proximity sensing mode. 
         [0100]    Embodiments can enable touch inputs to be entered on a conductive surface. Such embodiments can provide highly desirable aesthetic by enabling a contiguous metallic surface to serve as a touch surface. In addition, such embodiments can provide for more water resistant designs, as a contiguous sensing surface can be formed from a single metal sheet. 
         [0101]    It should be appreciated that reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Therefore, it is emphasized and should be appreciated that two or more references to “an embodiment” or “one embodiment” or “an alternative embodiment” in various portions of this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures or characteristics may be combined as suitable in one or more embodiments of the invention. 
         [0102]    Similarly, it should be appreciated that in the foregoing description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claims require more features than are expressly recited in each claim. Rather, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention.