Touch sensor with simultaneously driven drive electrodes

In one embodiment, a method comprises generating, by a controller, a plurality of drive signals. The method further includes simultaneously transmitting, by the controller, the plurality of drive signals to a plurality of drive electrodes disposed on a touch sensor. The method further includes sensing a sense electrode of a plurality of sense electrodes disposed on the touch sensor. The sensing comprises measuring, for each drive electrode of the plurality of drive electrodes, at least one value indicative of a capacitance between the sense electrode and the drive electrode.

TECHNICAL FIELD

This disclosure relates generally to touch sensors.

BACKGROUND

A touch sensor may detect the presence and location of a touch or the proximity of an object (such as a user's finger or a stylus) within a touch-sensitive area of the touch sensor overlaid on a display screen, for example. In a touch-sensitive-display application, the touch sensor may enable a user to interact directly with what is displayed on the screen, rather than indirectly with a mouse or touch pad. A touch sensor may be attached to or provided as part of a desktop computer, laptop computer, tablet computer, personal digital assistant (PDA), smartphone, satellite navigation device, portable media player, portable game console, kiosk computer, point-of-sale device, or other suitable device. A control panel on a household or other appliance may include a touch sensor.

There are a number of different types of touch sensors, such as (for example) resistive touch screens, surface acoustic wave touch screens, and capacitive touch screens. Herein, reference to a touch sensor may encompass a touch screen, and vice versa, where appropriate. When an object touches or comes within proximity of the surface of the capacitive touch screen, a change in capacitance may occur within the touch screen at the location of the touch or proximity. A touch-sensor controller may process the change in capacitance to determine its position on the touch screen.

DESCRIPTION OF EXAMPLE EMBODIMENTS

FIG. 1illustrates an example touch sensor10with an example touch-sensor controller12. Touch sensor10and touch-sensor controller12may detect the presence and location of a touch or the proximity of an object within a touch-sensitive area of touch sensor10. Herein, reference to a touch sensor may encompass both the touch sensor and its touch-sensor controller, where appropriate. Similarly, reference to a touch-sensor controller may encompass both the touch-sensor controller and its touch sensor, where appropriate. Touch sensor10may include one or more touch-sensitive areas, where appropriate. Touch sensor10may include an array of drive and sense electrodes (or an array of electrodes of a single type) disposed on one or more substrates, which may be made of a dielectric material. Herein, reference to a touch sensor may encompass both the electrodes of the touch sensor and the substrate(s) that they are disposed on, where appropriate. Alternatively, where appropriate, reference to a touch sensor may encompass the electrodes of the touch sensor, but not the substrate(s) that they are disposed on.

An electrode (whether a ground electrode, a guard electrode, a drive electrode, or a sense electrode) may be an area of conductive material forming a shape, such as for example a disc, square, rectangle, thin line, other suitable shape, or suitable combination of these. One or more cuts in one or more layers of conductive material may (at least in part) create the shape of an electrode, and the area of the shape may (at least in part) be bounded by those cuts. In particular embodiments, the conductive material of an electrode may occupy approximately 100% of the area of its shape. As an example and not by way of limitation, an electrode may be made of a transparent material such as indium tin oxide (ITO) and the ITO of the electrode may occupy approximately 100% of the area of its shape (sometimes referred to as 100% fill), where appropriate. In particular embodiments, the conductive material of an electrode may occupy substantially less than 100% of the area of its shape. As an example and not by way of limitation, an electrode may be made of one or more opaque materials such as fine lines of metal or other conductive material (FLM), such as for example copper, silver, or a copper- or silver-based material, and the fine lines of conductive material may occupy approximately 5% of the area of its shape in a hatched, mesh, or other suitable pattern. Herein, reference to FLM encompasses such material, where appropriate. Although this disclosure describes or illustrates particular electrodes made of particular conductive material forming particular shapes with particular fill percentages having particular patterns, this disclosure contemplates any suitable electrodes made of any suitable conductive material forming any suitable shapes with any suitable fill percentages having any suitable patterns.

Where appropriate, the shapes of the electrodes (or other elements) of a touch sensor may constitute in whole or in part one or more macro-features of the touch sensor. One or more characteristics of the implementation of those shapes (such as, for example, the conductive materials, fills, or patterns within the shapes) may constitute in whole or in part one or more micro-features of the touch sensor. One or more macro-features of a touch sensor may determine one or more characteristics of its functionality, and one or more micro-features of the touch sensor may determine one or more optical features of the touch sensor, such as transmittance, refraction, or reflection.

A mechanical stack may contain the substrate (or multiple substrates) and the conductive material forming the drive or sense electrodes of touch sensor10. As an example and not by way of limitation, the mechanical stack may include a first layer of optically clear adhesive (OCA) beneath a cover panel. The cover panel may be clear and made of a resilient material suitable for repeated touching, such as for example glass, polycarbonate, or poly(methyl methacrylate) (PMMA). This disclosure contemplates any suitable cover panel made of any suitable material. The first layer of OCA may be disposed between the cover panel and the substrate with the conductive material forming the drive or sense electrodes. The mechanical stack may also include a second layer of OCA and a dielectric layer (which may be made of PET or another suitable material, similar to the substrate with the conductive material forming the drive or sense electrodes). As an alternative, where appropriate, a thin coating of a dielectric material may be applied instead of the second layer of OCA and the dielectric layer. The second layer of OCA may be disposed between the substrate with the conductive material making up the drive or sense electrodes and the dielectric layer, and the dielectric layer may be disposed between the second layer of OCA and an air gap to a display of a device including touch sensor10and touch-sensor controller12. As an example only and not by way of limitation, the cover panel may have a thickness of approximately 1 mm; the first layer of OCA may have a thickness of approximately 0.05 mm; the substrate with the conductive material forming the drive or sense electrodes may have a thickness of approximately 0.05 mm; the second layer of OCA may have a thickness of approximately 0.05 mm; and the dielectric layer may have a thickness of approximately 0.05 mm. Although this disclosure describes a particular mechanical stack with a particular number of particular layers made of particular materials and having particular thicknesses, this disclosure contemplates any suitable mechanical stack with any suitable number of any suitable layers made of any suitable materials and having any suitable thicknesses. As an example and not by way of limitation, in particular embodiments, a layer of adhesive or dielectric may replace the dielectric layer, second layer of OCA, and air gap described above, with there being no air gap to the display.

In particular embodiments, the mechanical stack containing the substrate and the drive or sense electrodes may be formed within a display panel (thus forming an in-cell sensor) or on a display panel (thus forming an on-cell sensor). In an in-cell sensor, the display may be on the same substrate as the drive or sense electrodes. The display panel may be a liquid crystal display (LCD), a light-emitting diode (LED) display, an LED-backlight LCD, or other suitable electronic display and may be visible through the touch sensor10that provides the touch-sensitive area. Although this disclosure describes particular display types, this disclosure contemplates any suitable display types.

One or more portions of the substrate of touch sensor10may be made of polyethylene terephthalate (PET) or another suitable material. This disclosure contemplates any suitable substrate with any suitable portions made of any suitable material. In particular embodiments, the drive or sense electrodes in touch sensor10may be made of ITO in whole or in part. In particular embodiments, the drive or sense electrodes in touch sensor10may be made of fine lines of metal or other conductive material. As an example and not by way of limitation, one or more portions of the conductive material may be copper or copper-based and have a thickness of approximately 5 μm or less and a width of approximately 10 μm or less. As another example, one or more portions of the conductive material may be silver or silver-based and similarly have a thickness of approximately 5 μm or less and a width of approximately 10 μm or less. This disclosure contemplates any suitable electrodes made of any suitable material.

Touch sensor10may implement a capacitive form of touch sensing. In a mutual-capacitance implementation, touch sensor10may include an array of drive and sense electrodes forming an array of capacitive nodes. A drive electrode and a sense electrode may form a capacitive node. The drive and sense electrodes forming the capacitive node may come near each other, but not make electrical contact with each other. Instead, the drive and sense electrodes may be capacitively coupled to each other across a space between them. A pulsed or alternating voltage applied to the drive electrode (by touch-sensor controller12) may induce a charge on the sense electrode, and the amount of charge induced may be susceptible to external influence (such as a touch or the proximity of an object). When an object touches or comes within proximity of the capacitive node, a change in capacitance may occur at the capacitive node and touch-sensor controller12may measure the change in capacitance. By measuring changes in capacitance throughout the array, touch-sensor controller12may determine the position of the touch or proximity within the touch-sensitive area(s) of touch sensor10.

In a self-capacitance implementation, touch sensor10may include an array of electrodes of a single type that may each form a capacitive node. When an object touches or comes within proximity of the capacitive node, a change in self-capacitance may occur at the capacitive node and touch-sensor controller12may measure the change in capacitance, for example, as a change in the amount of charge needed to raise the voltage at the capacitive node by a pre-determined amount. As with a mutual-capacitance implementation, by measuring changes in capacitance throughout the array, touch-sensor controller12may determine the position of the touch or proximity within the touch-sensitive area(s) of touch sensor10. This disclosure contemplates any suitable form of capacitive touch sensing, where appropriate.

In particular embodiments, one or more drive electrodes may together form a drive line running horizontally or vertically or in any suitable orientation. Similarly, one or more sense electrodes may together form a sense line running horizontally or vertically or in any suitable orientation. In particular embodiments, drive lines may run substantially perpendicular to sense lines. Herein, reference to a drive line may encompass one or more drive electrodes making up the drive line, and vice versa, where appropriate. Similarly, reference to a sense line may encompass one or more sense electrodes making up the sense line, and vice versa, where appropriate.

Touch sensor10may have drive and sense electrodes disposed in a pattern on one side of a single substrate. In such a configuration, a pair of drive and sense electrodes capacitively coupled to each other across a space between them may form a capacitive node. For a self-capacitance implementation, electrodes of only a single type may be disposed in a pattern on a single substrate. In addition or as an alternative to having drive and sense electrodes disposed in a pattern on one side of a single substrate, touch sensor10may have drive electrodes disposed in a pattern on one side of a substrate and sense electrodes disposed in a pattern on another side of the substrate. Moreover, touch sensor10may have drive electrodes disposed in a pattern on one side of one substrate and sense electrodes disposed in a pattern on one side of another substrate. In such configurations, an intersection of a drive electrode and a sense electrode may form a capacitive node. Such an intersection may be a location where the drive electrode and the sense electrode “cross” or come nearest each other in their respective planes. The drive and sense electrodes do not make electrical contact with each other—instead they are capacitively coupled to each other across a dielectric at the intersection. Although this disclosure describes particular configurations of particular electrodes forming particular nodes, this disclosure contemplates any suitable configuration of any suitable electrodes forming any suitable nodes. Moreover, this disclosure contemplates any suitable electrodes disposed on any suitable number of any suitable substrates in any suitable patterns.

As described above, a change in capacitance at a capacitive node of touch sensor10may indicate a touch or proximity input at the position of the capacitive node. Touch-sensor controller12may detect and process the change in capacitance to determine the presence and location of the touch or proximity input. Touch-sensor controller12may then communicate information about the touch or proximity input to one or more other components (such one or more central processing units (CPUs)) of a device that includes touch sensor10and touch-sensor controller12, which may respond to the touch or proximity input by initiating a function of the device (or an application running on the device). Although this disclosure describes a particular touch-sensor controller having particular functionality with respect to a particular device and a particular touch sensor, this disclosure contemplates any suitable touch-sensor controller having any suitable functionality with respect to any suitable device and any suitable touch sensor.

Touch-sensor controller12may be one or more integrated circuits (ICs), such as for example general-purpose microprocessors, microcontrollers, programmable logic devices or arrays, application-specific ICs (ASICs). In particular embodiments, touch-sensor controller12comprises analog circuitry, digital logic, and digital non-volatile memory. In particular embodiments, touch-sensor controller12is disposed on a flexible printed circuit (FPC) bonded to the substrate of touch sensor10, as described below. The FPC may be active or passive, where appropriate. In particular embodiments, multiple touch-sensor controllers12are disposed on the FPC. Touch-sensor controller12may include a processor unit, a drive unit, a sense unit, and a storage unit. The drive unit may supply drive signals to the drive electrodes of touch sensor10. The sense unit may sense charge at the capacitive nodes of touch sensor10and provide measurement signals to the processor unit representing capacitances at the capacitive nodes. The processor unit may control the supply of drive signals to the drive electrodes by the drive unit and process measurement signals from the sense unit to detect and process the presence and location of a touch or proximity input within the touch-sensitive area(s) of touch sensor10. The processor unit may also track changes in the position of a touch or proximity input within the touch-sensitive area(s) of touch sensor10. The storage unit may store programming for execution by the processor unit, including programming for controlling the drive unit to supply drive signals to the drive electrodes, programming for processing measurement signals from the sense unit, and other suitable programming, where appropriate. Although this disclosure describes a particular touch-sensor controller having a particular implementation with particular components, this disclosure contemplates any suitable touch-sensor controller having any suitable implementation with any suitable components.

Tracks14of conductive material disposed on the substrate of touch sensor10may couple the drive or sense electrodes of touch sensor10to connection pads16, also disposed on the substrate of touch sensor10. As described below, connection pads16facilitate coupling of tracks14to touch-sensor controller12. Tracks14may extend into or around (e.g. at the edges of) the touch-sensitive area(s) of touch sensor10. Particular tracks14may provide drive connections for coupling touch-sensor controller12to drive electrodes of touch sensor10, through which the drive unit of touch-sensor controller12may supply drive signals to the drive electrodes. Other tracks14may provide sense connections for coupling touch-sensor controller12to sense electrodes of touch sensor10, through which the sense unit of touch-sensor controller12may sense charge at the capacitive nodes of touch sensor10. Tracks14may be made of fine lines of metal or other conductive material. As an example and not by way of limitation, the conductive material of tracks14may be copper or copper-based and have a width of approximately 100 μm or less. As another example, the conductive material of tracks14may be silver or silver-based and have a width of approximately 100 μm or less. In particular embodiments, tracks14may be made of ITO in whole or in part in addition or as an alternative to fine lines of metal or other conductive material. Although this disclosure describes particular tracks made of particular materials with particular widths, this disclosure contemplates any suitable tracks made of any suitable materials with any suitable widths. In addition to tracks14, touch sensor10may include one or more ground lines terminating at a ground connector (which may be a connection pad16) at an edge of the substrate of touch sensor10(similar to tracks14).

Connection pads16may be located along one or more edges of the substrate, outside the touch-sensitive area(s) of touch sensor10. As described above, touch-sensor controller12may be on an FPC. Connection pads16may be made of the same material as tracks14and may be bonded to the FPC using an anisotropic conductive film (ACF). Connection18may include conductive lines on the FPC coupling touch-sensor controller12to connection pads16, in turn coupling touch-sensor controller12to tracks14and to the drive or sense electrodes of touch sensor10. In another embodiment, connection pads16may be connected to an electro-mechanical connector (such as a zero insertion force wire-to-board connector); in this embodiment, connection18may not need to include an FPC. This disclosure contemplates any suitable connection18between touch-sensor controller12and touch sensor10.

FIG. 2illustrates an example touch-sensor controller12aconfigured to simultaneously drive a plurality of drive electrodes102of an example touch sensor10a. Touch sensor10aalso includes a plurality of sense electrodes104and tracks14. Touch-sensor controller12aincludes drive unit108and sense unit109. Touch sensor10a, drive electrodes102, sense electrodes104, tracks14aand14b, touch-sensor controller12a, drive unit108, and sense unit109may respectively have any suitable characteristics of touch sensor10, the drive electrodes, the sense electrodes, tracks14, touch-sensor controller12, the drive unit, and the sense unit described above in connection withFIG. 1.

In operation, controller12amay supply drive signals to drive electrodes102via drive unit108. In particular embodiments, each of the drive signals has a different dominant frequency. Accordingly, multiple drive electrodes102may each be driven at a different frequency. In particular embodiments, multiple drive electrodes102are driven simultaneously. The drive signals may capacitively couple from drive electrodes102into sense electrodes104. Accordingly, each sense electrode104may carry a sense signal that includes frequency components from multiple drive signals (e.g., the drive signals present on the drive electrodes102that intersect with the particular sense electrode104). In operation, controller12amay also be operable to sense the sense electrodes104using one or more sense units109. Sense unit109may be operable to split the signal received from a sense electrode104into multiple signals that each correspond to one of the drive electrodes102. Thus, each split signal also corresponds to a capacitive node106of the sense electrode104. The split signals may include the frequency components of the drive signal present on the corresponding drive electrode102. Accordingly, in particular embodiments, a split signal may have the same dominant frequency as the dominant frequency of one of the drive signals. Each of the split signals may be analyzed by sense unit109to determine whether the split signal indicates that a touch has occurred at the corresponding capacitive node. Such embodiments allow a plurality of the drive electrodes102to be driven simultaneously and sensed simultaneously through one or more sense electrodes104. These embodiments provide various advantages over implementations that allow driving and sensing of only one drive electrode at a time. For example, for a given amount of time, a greater number of capacitive nodes106of touch sensor10amay be measured. This allows quicker measurement of the capacitive nodes106of touch sensor10aand more accurate touch detection since more samples may be obtained in a given amount of time.

As depicted, touch sensor10aincludes multiple drive electrodes102a-h. The drive electrodes102may be arranged in any suitable configuration. For example, a drive electrode102may extend across touch sensor10ain a line or other suitable shape. In a particular embodiment, a drive electrode102extends across a portion of touch sensor10ain a particular direction. For example, in the embodiment depicted, each drive electrode102extends across touch sensor10ain a horizontal direction. Touch sensor10amay include any suitable number of drive electrodes102. In particular embodiments, each drive electrode102is electrically isolated from each other drive electrode102. That is, an electrically conductive element does not couple a drive electrode102to another drive electrode102.

Touch sensor10aalso includes multiple sense electrodes104a-h. The sense electrodes104may be arranged in any suitable configuration. For example, a sense electrode104may extend across touch sensor10ain a line or other suitable shape. In a particular embodiment, a sense electrode104extends across a portion of touch sensor10ain a particular direction. For example, in the embodiment depicted, each sense electrode104extends across touch sensor10ain a vertical direction. Touch sensor10amay include any suitable number of sense electrodes104. In particular embodiments, each sense electrode104is electrically isolated from each other sense electrode104. That is, an electrically conductive element does not couple a sense electrode104to another sense electrode104.

Capacitive nodes106may be formed at the intersection of the drive electrodes102and the sense electrodes104. As described above, an intersecting drive electrode102and sense electrode104may be capacitively coupled to each other across a space between them. As examples, the intersection between drive electrode102aand sense electrode104aforms capacitive node106a, the intersection between drive electrode102band sense electrode104bforms capacitive node106b, and the intersection between drive electrode102fand sense electrode104cforms capacitive node106c.

Touch sensor10aalso includes tracks14a. Tracks14acouple to drive electrodes102and facilitate connection of the drive electrodes102to touch-sensor controller12a. For example, as described above, each track14amay couple one or more drive electrodes102to a connection pad (such as connection pad16described above) of touch sensor10a. A connector (such as connection18described above) may couple the connection pad to touch-sensor controller12a. Touch sensor10amay include any suitable number of tracks14a. For example, touch sensor10amay include a track14afor each drive electrode102. As another example, at least one of the tracks14amay be coupled to multiple drive electrodes102such that there are more drive electrodes102than tracks14a.

Touch sensor10aalso includes tracks14b. Tracks14bcouple to sense electrodes104and facilitate connection of the sense electrodes104to touch-sensor controller12a. For example, as described above, each track14bmay couple one or more sense electrodes104to a connection pad (such as connection pad16described above) of touch sensor10a. A connector (such as connector18described above) may couple the connection pad to touch-sensor controller12a. Touch sensor10amay include any suitable number of tracks14b. For example, touch sensor10amay include a track14bfor each sense electrode104. As another example, at least one of the tracks14bmay be coupled to multiple sense electrodes104such that there are more sense electrodes104than tracks14b.

As depicted, touch-sensor controller12aincludes drive unit108. Drive unit108is coupled to drive electrodes102via tracks14a. Drive unit108is operable to generate drive signals and transmit the drive signals to the drive electrodes102. Drive unit108may generate any suitable drive signals. A drive signal may include a sin wave, a square wave, a triangle wave, a wave with periodic pulses, or other suitable signal having shaped pulses. The drive signal may have any suitable dominant frequency. The dominant frequency is the frequency at which the spectrum content of the drive signal is the greatest. In particular embodiments, a drive signal may include spectrum content at the dominant frequency of the drive signal and at any suitable number of harmonics of the dominant frequency.

In particular embodiments, drive unit108generates multiple different drive signals that each have a different dominant frequency. Each drive signal may be transmitted from drive unit108to a set of one or more drive electrodes102. In a particular embodiment, a plurality of drive electrodes102are each simultaneously driven by a separate drive signal. Accordingly, each drive electrode102of at least a subset of the drive electrodes102of touch sensor10amay be driven by a drive signal having a dominant frequency that is different from the dominant frequency of each other drive signal. In various embodiments, each drive electrode102of touch sensor10ais simultaneously driven by a separate drive signal having a dominant frequency that is different from the dominant frequencies of the other drive signals. In particular embodiments, groups of drive electrodes102are successively driven by drive signals having different dominant frequencies. Thus, a first group of drive electrodes102(e.g., drive electrodes102a-d) may be driven with four drive signals that each have a different dominant frequency for a first period of time, then a second group of drive electrodes (e.g., drive electrodes102e-h) may be driven with four drive signals that each have a different dominant frequency for a second period of time, and so on. In particular embodiments, the set of drive signals that drive a group of drive electrodes102may have the same dominant frequencies as the other sets of drive signals used to drive the other groups.

FIG. 3depicts frequency domain representations300of various drive signals that may be generated by drive unit108and sense signals that may be analyzed by controller12a. The horizontal axes of representations300depict frequency and the vertical axes depict the amplitude of the power of the signals represented. Frequency domain representation300aincludes waveforms302of a plurality of drive signals that may be generated by drive unit108. For example, waveform302adepicts the frequency content of a first drive signal that has a dominant frequency at303a, waveform302bdepicts the frequency content of a second drive signal that has a dominant frequency at303b, and so on. As depicted in representation300a, each drive signal has a different dominant frequency.

In particular embodiments, each drive signal generated by drive unit108is transmitted to a set of one or more drive electrodes102. For example, the drive signal represented by waveform302amay be transmitted to drive electrode102a, the drive signal represented by waveform302bmay be transmitted to drive electrode102b, the drive signal represented by waveform302cmay be transmitted to drive electrode102c, and so on. As another example, a single drive signal may be transmitted to multiple drive electrodes102in succession. For example, if the drive signals represented by waveforms302e-hare omitted, the drive signal represented by waveform302amay be transmitted to drive electrodes102aand then102e, the drive signal represented by waveform302bmay be transmitted to drive electrodes102band then102f, the drive signal represented by waveform302cmay be transmitted to drive electrodes102cand then102g, and the drive signal represented by waveform302dmay be transmitted to drive electrodes102dand then102h. Thus in various different embodiments, multiple drive electrodes102of touch sensor10aare simultaneously driven with drive signals having different dominant frequencies.

When the drive signals are received by drive electrodes102, the drive signals may capacitively couple into the sense electrodes104. For example, a portion of each drive signal carried by a drive electrode102may be capacitively coupled into a sense electrode that intersects with the drive electrodes102, such as sense electrode104a. Frequency domain representation300bofFIG. 3depicts a waveform304of a sense signal that may be present on one of the sense electrodes, such as sense electrode104a. As depicted, waveform304includes attenuated frequency components from each of the drive signals depicted in waveform300a. Accordingly, the sense signal includes frequency components at each of the dominant frequencies303of the drive signals depicted in300a.

Sense unit109is operable to receive at least one sense signal from at least one sense electrode104, sense charge at the capacitive nodes116associated with the sense electrode104, and provide measurement signals representing capacitances at the capacitive nodes116. In particular embodiments, any one or more of these functions may be performed concurrently with the transmission of the drive signals to the drive electrodes102. In the embodiment depicted, sense unit109includes receiver front end110, demultiplexer111, frequency splitter112, a plurality of filters114a, and a plurality of detectors116. The various components of sense unit109may be implemented by software, hardware, or a combination thereof.

Demultiplexer111is operable to pass a sense signal from a sense electrode104to receiver front end110. For example, demultiplexer111may receive sense signals from a plurality of sense electrodes104and select one sense electrode104at a time to be passed to receiver front end110. In particular embodiments, demultiplexer111allows a single set of hardware or software (e.g., receiver front end110, frequency splitter112, filters114, and detectors116) to analyze sense signals from multiple different sense electrodes104. As an alternative, demultiplexer111may be omitted and each sense electrode104may be coupled directly to its own sense unit109such that the sense signals of the sense electrodes104may be analyzed simultaneously by multiple sense units109instead of in succession by a single sense unit109. As another alternative, controller12amay include multiple sense units109and a demultiplexer111for each sense unit109that allows the sense unit109to analyze a plurality of sense signals in succession.

Receiver front end110may receive a sense signal from a sense electrode104and perform any suitable processing of the sense signal. For example, receiver front end110may integrate or aggregate the sense signal, amplify the sense signal, or equalize the sense signal (e.g., amplify or attenuate one or more portions of the drive signals in order to compensate for channel characteristics of sense electrode104that affect the drive signals differently). In particular embodiments, the sense signal may be integrated using a timescale that is small enough to preserve the frequency content information contained in the sense signal. In particular embodiments, receiver front end110is a low noise amplifier with an adjustable gain. In various embodiments, receiver front end110includes a bandpass filter that is operable to pass a range of frequencies that includes the dominant frequencies of the drive signals but filter frequencies outside of this range.

Frequency splitter112is operable to receive a signal and demodulate the signal. For example, frequency splitter112may receive a processed sense signal from receiver front end110and break out the signal into multiple signals that each carry a portion of the frequency content of the processed sense signal. In particular embodiments, frequency splitter112may demodulate the signal by multiplying the signal with a weight matrix. The demodulated signals may then pass through filters114that remove unwanted noise or amplify the signals before they are passed to detectors116. In a particular embodiment, filters114are narrow active filters.

Frequency domain representation300cofFIG. 3depicts waveforms306for each of the sense signals that are passed to detectors116. After demodulation and filtering, each signal represents the portion of a drive signal that was capacitively coupled into the sense electrode104. Accordingly, each signal represented by a waveform306may correspond to a drive electrode104and the capacitive node106aformed by the intersection of the sense electrode104and the particular drive electrode102. For example, the signal represented by waveform306acorresponds to drive electrode102aand capacitive node106a, the signal represented by waveform306bcorresponds to drive electrode102band the capacitive node formed by the sense electrode104and drive electrode102b.

Detectors116may process these signals and determine at least one value indicative of a capacitance of the respective capacitive node106. For example, detector116may measure an amount of charge of the signal, a voltage level of the signal, a phase delay of the signal, or other suitable characteristic of the signal. Detectors116may, alone or in combination with other hardware or software, determine a change in capacitance (or lack thereof) at the respective capacitive node106. For example, detector116may detect a change in amplitude of the signal at its input relative to a normal level of the signal and determine that the capacitance at the capacitive node106has changed relative to a previous measurement. Touch-sensor controller may analyze the results of multiple detectors116to determine a location of one or more touches or proximity inputs. Detector116may use any suitable techniques for determining where a touch or proximity input has occurred.

In particular embodiments, controller12amay also be operable to detect whether a touch occurring at a capacitive node106is caused by an active stylus or a passive object, such as a human finger. In particular embodiments, an active stylus used in combination with touch sensor10amay generate an electrical signal having any suitable characteristics of the drive signals described above. In a particular embodiment, the signal generated by the active stylus has a dominant frequency that is different from the drive signals transmitted to the drive electrodes102. The signal generated by the active stylus may capacitively couple into one or more sense electrodes104and this coupling may be detected by controller12a. For example, frequency splitter112and an additional filter114may isolate the signal generated by the active stylus and feed this signal to a detector116which may determine whether or not a touch measured by the other detectors116was caused by an active stylus.

FIG. 4illustrates an example method for simultaneously driving a plurality of drive electrodes102and sensing a sense electrode104. The method begins at step402where a plurality of drive signals are generated. Each of the drive signals may have a different dominant frequency. The drive signals may be generated by a drive unit108of a touch-sensor controller12a. At step404, the drive signals are simultaneously transmitted to drive electrodes102. Each drive electrode102may be driven at a unique frequency. Accordingly, multiple drive electrodes102may be driven simultaneously with different frequencies. Each of the drive signals carried by the drive electrodes102may capacitively couple into one or more sense electrodes104that intersect with the drive electrodes102.

At step406, a sense signal is received from a sense electrode104. The sense signal may include frequency components from each of the drive signals. After reception of the sense signal, any suitable processing may be performed to the sense signal. For example, the sense signal may be amplified, filtered, equalized, or otherwise processed. The processed signal is then passed to a frequency splitter.

At step408, the sense signal is split into a plurality of signals that each correspond to one of the drive electrodes102driven at step404. Accordingly, each split signal also corresponds to a capacitive node106formed by the respective drive electrode102and the sense electrode104. At step410, the split signals are analyzed to determine whether a touch occurred at the corresponding capacitive nodes106. For example, a change in amplitude of the split signal relative to a previous measurement of the same capacitive node106may indicate that the capacitance at the node has changed. A change in capacitance may indicate that a touch has occurred at the relevant capacitive node106. The split signals may also be compared with other split signals to determine where a touch has occurred. Step410may also involve analyzing one of the split signals to determine whether a touch was performed by an active stylus or a passive object. For example, if the amplitude of the split signal that corresponds to the dominant frequency of the active stylus is above a predetermined threshold, it may be determined that the touch was caused by the active stylus rather than a passive object. In particular embodiments, multiple sense electrodes104may be sensed simultaneously. Various embodiments provide the ability to detect simultaneous touches at different capacitive nodes106.

Particular embodiments may repeat the steps of the method ofFIG. 4, where appropriate. Moreover, although this disclosure describes and illustrates particular steps of the method ofFIG. 4as occurring in a particular order, this disclosure contemplates any suitable steps of the method ofFIG. 4occurring in any suitable order. Furthermore, although this disclosure describes and illustrates particular components, devices, or systems carrying out particular steps of the method ofFIG. 4, this disclosure contemplates any suitable combination of any suitable components, devices, or systems carrying out any suitable steps of the method ofFIG. 4.

FIG. 5illustrates an example stack36of touch sensor10and a display32. Stack36includes electrodes24formed on substrate22, a cover panel26coupled to substrate22via a layer of adhesive28, and a dielectric layer20applied to the bottom surface of substrate22and conductive material formed thereon. The dielectric layer20is configured to interface with display panel32. For example, as depicted, the dielectric layer20may face display panel32with an air gap31between the dielectric layer20and display panel32.

Particular embodiments of the present disclosure may provide one or more or none of the following technical advantages. In particular embodiments, drive electrodes of a touch sensor may be driven simultaneously. A technical advantage of one embodiment includes the ability to sense multiple capacitive nodes of a sense electrode simultaneously. Another technical advantage of one embodiment may include reducing the amount of time required to sense the capacitive nodes of a touch screen. Another technical advantage of one embodiment may include increasing the number of sense measurements that may be performed in a given amount of time. Another technical advantage includes simultaneously detecting a location of a touch by an active stylus and a different location of a touch by a different object, such as a finger or passive stylus. Certain embodiments of the present disclosure may include none, some, or all of the above technical advantages. One or more other technical advantages may be readily apparent to one skilled in the art in view of the figures, descriptions, and claims of the present disclosure.

Herein, reference to memory or a computer-readable non-transitory storage medium or media may include one or more semiconductor-based or other integrated circuits (ICs) (such, as for example, a field-programmable gate array (FPGA) or an application-specific IC (ASIC)), hard disk drives (HDDs), hybrid hard drives (HHDs), optical discs, optical disc drives (ODDs), magneto-optical discs, magneto-optical drives, floppy diskettes, floppy disk drives (FDDs), magnetic tapes, solid-state drives (SSDs), RAM-drives, SECURE DIGITAL cards, SECURE DIGITAL drives, any other suitable computer-readable non-transitory storage medium or media, or any suitable combination of two or more of these, where appropriate. A memory or computer-readable non-transitory storage medium or media may be volatile, non-volatile, or a combination of volatile and non-volatile, where appropriate.

This disclosure encompasses all changes, substitutions, variations, alterations, and modifications to the example embodiments herein that a person having ordinary skill in the art would comprehend. For example, the figures depicted herein are not necessarily drawn to scale and any suitable dimensions may be used for any of the components of the figures. Moreover, although this disclosure describes and illustrates respective embodiments herein as including particular components, elements, functions, operations, or steps, any of these embodiments may include any combination or permutation of any of the components, elements, functions, operations, or steps described or illustrated anywhere herein that a person having ordinary skill in the art would comprehend. Furthermore, reference in the appended claims to an apparatus or system or a component of an apparatus or system being adapted to, arranged to, capable of, configured to, enabled to, operable to, or operative to perform a particular function encompasses that apparatus, system, component, whether or not it or that particular function is activated, turned on, or unlocked, as long as that apparatus, system, or component is so adapted, arranged, capable, configured, enabled, operable, or operative.