Classifications

• • G—PHYSICS
  • G06—COMPUTING OR CALCULATING; COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
  • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
  • G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
  • G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
  • G06F3/044—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means by capacitive means
  • G06F3/0446—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means by capacitive means using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
  • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
  • G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
  • G01D5/14—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage
  • G01D5/24—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying capacitance
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
  • G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
  • G01R27/26—Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants ; Measuring impedance or related variables
  • G01R27/2605—Measuring capacitance
• • G—PHYSICS
  • G06—COMPUTING OR CALCULATING; COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
  • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
  • G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
  • G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
  • G06F3/0416—Control or interface arrangements specially adapted for digitisers
• • G—PHYSICS
  • G06—COMPUTING OR CALCULATING; COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
  • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
  • G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
  • G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
  • G06F3/0416—Control or interface arrangements specially adapted for digitisers
  • G06F3/0418—Control or interface arrangements specially adapted for digitisers for error correction or compensation, e.g. based on parallax, calibration or alignment
  • G06F3/04182—Filtering of noise external to the device and not generated by digitiser components
• • G—PHYSICS
  • G06—COMPUTING OR CALCULATING; COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
  • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
  • G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
  • G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
  • G06F3/044—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means by capacitive means

Definitions

• proximity sensor devices also commonly called touchpads or touch sensor devices
• a proximity sensor device typically includes a sensing region, often demarked by a surface, in which the proximity sensor device determines the presence, location and/or motion of one or more input objects.
• Proximity sensor devices may be used to provide interfaces for the electronic system.
• proximity sensor devices are often used as input devices for larger computing systems (such as opaque touchpads integrated in, or peripheral to, notebook or desktop computers).
• proximity sensor devices are also often used in smaller electronic devices/systems (such as touch screens integrated in cellular phones and tablet computers). Such touch screen input devices are typically superimposed upon or otherwise collocated with a display of the electronic device/system.
• a switch disposed between a sensor electrode and the second input of the differential amplifier is opened to initiate a reset phase where the sensor electrode and the differential amplifier are decoupled.
• a feedback capacitance disposed between the second input and the output is reset to a first level of charge.
• the switch is closed to initiate a measurement phase where the second input and the sensor electrode are coupled.
• charge is balanced between the sensor electrode and the feedback capacitance such that a sensor electrode voltage equals a voltage of the first input equals a voltage of the second input, and the sensor electrode is charged to a value proportional to its capacitance and the voltage of the second input; and the differential amplifier is utilized to integrate charge on the sensor electrode, such that an absolute capacitance is measured.
• Figure 1 is a block diagram of an example input device, in accordance with embodiments.
• Figure 2 shows a portion of an example sensor electrode pattern which may be utilized in a sensor to generate all or part of the sensing region of an input device, such as a touch screen, according to some embodiments.
• Figure 3 shows a comparison of diagrams of transcapacitive and conventional absolute capacitance sensing signals and modes.
• Figures 4A and 4B illustrate operation of a capacitance measurement circuit through a first half cycle of absolute capacitive sensing, according to an embodiment.
• Figure 5 shows a comparison of diagrams of transcapacitive and new (as described herein) absolute capacitance sensing signals and mode, in accordance with various embodiments.
• Figures 6A-6D illustrate operation of an capacitive measurement circuit through a full cycle of absolute capacitive sensing, according to an embodiment.
• Figure 7 illustrates a capacitance measurement circuit, according to an embodiment.
• Figure 8 illustrates a capacitance measurement circuit, according to some embodiments.
• Figures 9A-9C illustrate a method of capacitance measurement with a differential amplifier having an output and differential first and second input, according to various embodiments. DESCRIPTION OF EMBODIMENTS
• the input device may be a capacitive input device.
• FIG. 1 is a block diagram of an exemplary input device 100, in accordance with various embodiments.
• Input device 100 may be configured to provide input to an electronic system/device (not depicted).
• electronic system broadly refers to any system capable of electronically processing information.
• electronic systems include personal computers of all sizes and shapes, such as desktop computers, laptop computers, netbook computers, tablets, web browsers, e-book readers, and personal digital assistants (PDAs).
• PDAs personal digital assistants
• Additional example electronic systems include composite input devices, such as physical keyboards that include input device 100 and separate joysticks or key switches.
• Further example electronic systems include peripherals such as data input devices (including remote controls and mice), and data output devices (including display screens and printers).
• peripherals such as data input devices (including remote controls and mice), and data output devices (including display screens and printers).
• Other examples include remote terminals, kiosks, and video game machines (e.g., video game consoles, portable gaming devices, and the like).
• Other examples include communication devices (including cellular phones, such as smart phones), and media devices (including recorders, editors, and players such as televisions, set-top boxes, music players, digital photo frames, and digital cameras).
• the electronic systems could be a host or a slave to the input device.
• Input device 100 can be implemented as a physical part of an electronic system, or can be physically separate from an electronic system. As appropriate, input device 100 may communicate with parts of the electronic system using any one or more of the following: buses, networks, and other wired or wireless interconnections. Examples include, but are not limited to: Inter-Integrated Circuit (I2C), Serial Peripheral Interface (SPI), Personal System 2 (PS/2), Universal Serial Bus (USB), Bluetooth ®, Radio
• I2C Inter-Integrated Circuit
• SPI Serial Peripheral Interface
• PS/2 Personal System 2
• USB Universal Serial Bus
• Bluetooth ® Radio
• RF Frequency
• IrDA Infrared Data Association
• input device 100 is shown as a proximity sensor device (also often referred to as a "touchpad” or a “touch sensor device”) configured to sense input provided by one or more input objects 140 in a sensing region 120.
• Example input objects include fingers and styli, as shown in Figure 1 .
• Sensing region 120 encompasses any space above, around, in and/or near input device 100, in which input device 100 is able to detect user input (e.g., user input provided by one or more input objects 140).
• user input e.g., user input provided by one or more input objects 140.
• sensing region 120 extends from a surface of input device 100 in one or more directions into space until signal-to-noise ratios prevent sufficiently accurate object detection.
• the distance to which this sensing region 120 extends in a particular direction in various embodiments, may be on the order of less than a millimeter, millimeters, centimeters, or more, and may vary significantly with the type of sensing technology used and the accuracy desired.
• sense input that comprises no contact with any surfaces of input device 100, contact with an input surface (e.g., a touch surface) of input device 100, contact with an input surface of input device 100 coupled with some amount of applied force or pressure, and/or a combination thereof.
• input surfaces may be provided by surfaces of casings within which the sensor electrodes reside, by face sheets applied over the sensor electrodes or any casings, etc.
• sensing region 120 has a rectangular shape when projected onto an input surface of input device 100.
• Input device 100 may utilize any combination of sensor components and sensing technologies to detect user input in sensing region 120.
• Input device 100 comprises one or more sensing elements for detecting user input.
• input device 100 may use capacitive techniques.
• Some implementations are configured to provide images that span one, two, three, or higher dimensional spaces. Some implementations are configured to provide projections of input along particular axes or planes.
• Some capacitive implementations utilize arrays or other regular or irregular patterns of capacitive sensing elements to create electric fields.
• separate sensing elements may be ohmically shorted together to form larger sensor electrodes.
• Some capacitive implementations utilize resistive sheets, which may be uniformly resistive.
• Some capacitive implementations utilize “self capacitance” (or “absolute capacitance”) sensing methods based on changes in the capacitive coupling between sensor electrodes and an input object.
• an input object near the sensor electrodes alters the electric field near the sensor electrodes, thus changing the measured capacitive coupling.
• an absolute capacitance sensing method operates by modulating sensor electrodes with respect to a reference voltage (e.g., system ground), and by detecting the capacitive coupling between the sensor electrodes and input objects.
• transcapacitance sensing methods based on changes in the capacitive coupling between sensor electrodes.
• an input object near the sensor electrodes alters the electric field between the sensor electrodes, thus changing the measured capacitive coupling.
• a transcapacitive sensing method operates by detecting the capacitive coupling between one or more transmitter sensor electrodes (also “transmitter electrodes” or “transmitters”) and one or more receiver sensor electrodes (also “receiver electrodes” or “receivers”).
• transmitters and receivers may be referred to as sensor electrodes or sensor elements.
• Transmitter sensor electrodes may be modulated relative to a reference voltage (e.g., system ground) to transmit transmitter signals.
• Receiver sensor electrodes may be held substantially constant relative to the reference voltage to facilitate receipt of resulting signals.
• a resulting signal may comprise effect(s) corresponding to one or more transmitter signals, and/or to one or more sources of environmental interference (e.g., other electromagnetic signals).
• Sensor electrodes may be dedicated transmitters or receivers, or may be configured to both transmit and receive.
• one or more receiver electrodes may be operated to receive a resulting signal when no transmitter electrodes are transmitting (e.g., the transmitters are disabled). In this manner, the resulting signal represents noise detected in the operating environment of sensing region 120.
• a processing system 1 10 is shown as part of input device 100.
• Processing system 1 10 is configured to operate the hardware of input device 100 to detect input in sensing region 120.
• Processing system 1 10 comprises parts of or all of one or more integrated circuits (ICs) and/or other circuitry components.
• ICs integrated circuits
• a processing system for a mutual capacitance sensor device may comprise transmitter circuitry configured to transmit signals with transmitter sensor electrodes, and/or receiver circuitry configured to receive signals with receiver sensor electrodes).
• processing system 1 10 also comprises electronically-readable instructions, such as firmware code, software code, and/or the like.
• components composing processing system 1 10 are located together, such as near sensing element(s) of input device 100.
• components of processing system 1 10 are physically separate with one or more components close to sensing element(s) of input device 100, and one or more components elsewhere.
• input device 100 may be a peripheral coupled to a desktop computer, and processing system 1 10 may comprise software configured to run on a central processing unit of the desktop computer and one or more ICs (perhaps with associated firmware) separate from the central processing unit.
• input device 100 may be physically integrated in a phone, and processing system 1 10 may comprise circuits and firmware that are part of a main processor of the phone.
• processing system 1 10 is dedicated to implementing input device 100.
• processing system 1 10 also performs other functions, such as operating display screens, driving haptic actuators, etc.
• Processing system 1 10 may be implemented as a set of modules that handle different functions of processing system 1 10. Each module may comprise circuitry that is a part of processing system 1 10, firmware, software, or a combination thereof. In various embodiments, different combinations of modules may be used.
• Example modules include hardware operation modules for operating hardware such as sensor electrodes and display screens, data processing modules for processing data such as sensor signals and positional information, and reporting modules for reporting information. Further example modules include sensor operation modules configured to operate sensing element(s) to detect input, identification modules configured to identify gestures such as mode changing gestures, and mode changing modules for changing operation modes.
• processing system 1 10 responds to user input (or lack of user input) in sensing region 120 directly by causing one or more actions.
• Example actions include changing operation modes, as well as GUI actions such as cursor movement, selection, menu navigation, and other functions.
• processing system 1 10 provides information about the input (or lack of input) to some part of the electronic system (e.g., to a central processing system of the electronic system that is separate from processing system 1 10, if such a separate central processing system exists).
• some part of the electronic system processes information received from processing system 1 10 to act on user input, such as to facilitate a full range of actions, including mode changing actions and GUI actions.
• processing system 1 10 operates the sensing element(s) of input device 100 to produce electrical signals indicative of input (or lack of input) in sensing region 120.
• Processing system 1 10 may perform any appropriate amount of processing on the electrical signals in producing the information provided to the electronic system.
• processing system 1 10 may digitize analog electrical signals obtained from the sensor electrodes.
• processing system 1 10 may perform filtering or other signal conditioning.
• processing system 1 10 may subtract or otherwise account for a baseline, such that the information reflects a difference between the electrical signals and the baseline.
• processing system 1 10 may determine positional information, recognize inputs as commands, recognize handwriting, and the like.
• Positional information as used herein broadly encompasses absolute position, relative position, velocity, acceleration, and other types of spatial information.
• Exemplary "zero-dimensional” positional information includes near/far or contact/no contact information.
• Exemplary "one-dimensional” positional information includes positions along an axis.
• Exemplary "two-dimensional” positional information includes motions in a plane.
• Exemplary "three-dimensional” positional information includes instantaneous or average velocities in space. Further examples include other representations of spatial information.
• Historical data regarding one or more types of positional information may also be determined and/or stored, including, for example, historical data that tracks position, motion, or instantaneous velocity over time.
• input device 100 is implemented with additional input components that are operated by processing system 1 10 or by some other processing system. These additional input components may provide redundant functionality for input in sensing region 120, or some other functionality.
• Figure 1 shows buttons 130 near sensing region 120 that can be used to facilitate selection of items using input device 100.
• Other types of additional input components include sliders, balls, wheels, switches, and the like.
• input device 100 may be implemented with no other input components.
• input device 100 may be a touch screen, and sensing region 120 overlaps at least part of an active area of a display screen.
• input device 100 may comprise substantially transparent sensor electrodes overlaying the display screen and provide a touch screen interface for an associated electronic system.
• the display screen may be any type of dynamic display capable of displaying a visual interface to a user, and may include any type of light emitting diode (LED), organic LED (OLED), cathode ray tube (CRT), liquid crystal display (LCD), plasma, electroluminescence (EL), or other display technology.
• Input device 100 and the display screen may share physical elements.
• some embodiments may utilize some of the same electrical components for displaying and sensing.
• the display screen may be operated in part or in total by processing system 1 10.
• the mechanisms are capable of being distributed as a program product (e.g., software) in a variety of forms.
• the mechanisms that are described may be implemented and distributed as a software program on information bearing media that are readable by electronic processors (e.g., non-transitory computer- readable and/or recordable/writable information bearing media readable by processing system 1 10).
• the embodiments apply equally regardless of the particular type of medium used to carry out the distribution. Examples of non-transitory, electronically readable media include various discs, memory sticks, memory cards, memory modules, and the like.
• Electronically readable media may be based on flash, optical, magnetic, holographic, or any other tangible storage technology.
• FIG. 2 shows a portion of an example sensor electrode pattern 200 which may be utilized in a sensor to generate all or part of the sensing region of a input device 100, according to various embodiments.
• Input device 100 is configured as a capacitive input device when utilized with a capacitive sensor electrode pattern.
• a non-limiting simple rectangular sensor electrode pattern 200 is illustrated. It is appreciated that numerous other sensor electrode patterns may be employed including patterns with a single set of sensor electrodes, patterns with two sets of sensor electrodes disposed in a single layer (without overlapping), and patterns that provide individual button electrodes.
• the illustrated sensor electrode pattern is made up of a plurality of receiver electrodes 270 (270-0, 270-1 , 270-2 ...
• Capacitive pixel 290 illustrates one of the capacitive pixels generated by sensor electrode pattern 200 during transcapacitive sensing. It is appreciated that in a crossing sensor electrode pattern, such as the illustrated example, some form of insulating material or substrate is typically disposed between transmitter electrodes 260 and receiver electrodes 270. However, in some embodiments, transmitter electrodes 260 and receiver electrodes 270 may be disposed on the same layer as one another through use of routing techniques and/or jumpers.
• touch sensing includes sensing input objects anywhere in sensing region 120 and may comprise: no contact with any surfaces of the input device 100, contact with an input surface (e.g., a touch surface) of the input device 100, contact with an input surface of the input device 100 coupled with some amount of applied force or pressure, and/or a combination thereof.
• an input surface e.g., a touch surface
• capacitive pixels are areas of localized capacitive coupling between transmitter electrodes 260 and receiver electrodes 270.
• the capacitive coupling between transmitter electrodes 260 and receiver electrodes 270 changes with the proximity and motion of input objects in the sensing region associated with transmitter electrodes 260 and receiver electrodes 270.
• sensor electrode pattern 200 is "scanned" to determine these capacitive couplings. That is, the transmitter electrodes 260 are driven to transmit transmitter signals. Transmitters may be operated such that one transmitter electrode transmits at one time, or multiple transmitter electrodes transmit at the same time.
• these multiple transmitter electrodes may transmit the same transmitter signal and produce an effectively larger transmitter electrode, or these multiple transmitter electrodes may transmit different transmitter signals.
• multiple transmitter electrodes may transmit different transmitter signals according to one or more coding schemes that enable their combined effects on the resulting signals of receiver electrodes 270 to be independently determined.
• the receiver electrodes 270 may be operated singly or multiply to acquire resulting signals.
• the resulting signals may be used to determine measurements of the capacitive couplings at the capacitive pixels.
• a set of measurements from the capacitive pixels form a “capacitive image” (also “capacitive frame”) representative of the capacitive couplings at the pixels.
• Capacitive image also “capacitive frame”
• Multiple capacitive images may be acquired over multiple time periods, and differences between them used to derive information about input in the sensing region. For example, successive capacitive images acquired over successive periods of time can be used to track the motion(s) of one or more input objects entering, exiting, and within the sensing region.
• one or more sensor electrodes 260 or 270 may be operated to perform absolute capacitive sensing at a particular instance of time. For example, receiver electrode 270-0 may be charged and then the capacitance of receiver electrode 270-0 may be measured. In such an embodiment, an input object 140 interacting with receiver electrode 270-0 alters the electric field near receiver electrode 270-0, thus changing the measured capacitive coupling. In this same manner, a plurality of sensor electrodes 270 may be used to measure absolute capacitance and/or a plurality of sensor electrodes 260 may be used to measure absolute capacitance.
• Figure 3 shows a comparison of diagrams of transcapacitive and conventional absolute capacitance sensing signals and modes (310 and 320 respectively).
• portion 310 illustrates transmitter and integrated resulting signals ⁇ V Tr ansinput and V Tra nsout respectively) for a transcapacitive sensing mode, where 31 1 is a first half of a
• transcapacitive sensing cycle and 312 is a second half of a transcapacitive sensing cycle.
• Each half transcapacitive sensing cycle (31 1 , 312) comprises an integration time period, Trransintegmte, and a reset time period, T TransReset .
• portion 320 illustrates transmitter and integrated resulting signals ⁇ V C0 nvAbsinput and V Con vAbsout respectively) for an absolute capacitive sensing mode wherein 321 is the first half of a conventional absolute sensing cycle and 322 is the second half of the conventional absolute capacitive sensing cycle.
• Each half (321 , 322) comprises one pre-charge time period, T Abs precharge, and one integration time period, T Abs i n tegrate-
• the transmitter and resulting signals differ for the two sensing modes.
• the illustrated conventional absolute capacitive sensing mode comprises a pre-charge phase, T AbsPr charge, in which a sensor electrode is charged up to "voltage high" by the transmitter signal followed by an integration phase, T Abs!nt egrate, in which the sensor electrode is discharged and the resulting charge flow from the resulting signal is integrated and measured.
• the maximum amount of charge that may be measured by a capacitive measuring circuit coupled to the sensor electrode is C B ⁇ V dd 1 2) where C B is the absolute capacitance (background capacitance + any input object capacitance) being measured and V dd is the receiver supply voltage (reference voltage or an operating voltage).
• C B is the absolute capacitance (background capacitance + any input object capacitance) being measured
• V dd the receiver supply voltage (reference voltage or an operating voltage).
• T Abs prechaiye, and the integration phase, T Abs i ntegrate , durations may be based on the settling time of the sensor electrode, T abs . This settling time precludes shortening these times without impact on the ability to sense.
• the transcapacitive sensing reset phase, T TransReset is much shorter than the conventional absolute sensing pre-charge ⁇ T Abs p re charge) or absolute sensing integrate phase ⁇ T Abs i nt egrate) which is less than the transcapacitive sensing integrate time, T Tra nsReset « aAbs precharge ⁇ rransinegmte- Therefore, the duration of a half sensing cycle for the conventional absolute capacitive sensing method, T Abs p re charge + T Abs i nt egrate, is typically greater than the duration of a half sensing cycle for transcapacitive sensing method, T Tra nsReset + T Tr ansintegrate- Further, since the half sensing cycle for the conventional absolute capacitive sensing method is greater than the half sensing cycle for transcapacitive sensing method, the transmitter signal frequency for absolute capacitive sensing is lower than the transmitter signal frequency for transcapacitive sensing.
• sensing frequency of an absolute capacitive sensing device may be improved (shortened), as compared to conventional techniques, by altering parameters of circuits and techniques used for performing absolute capacitive sensing.
• increasing the amplitude and/or the frequency of transmitter signal may improve performance of the sensing device in comparison to conventional techniques of absolute capacitive sensing.
• the signal-to-noise ratio may be increased, interference susceptibility may be improved and proximity sensing (distance and accuracy) may be improved by one or more of increasing the amplitude and/or frequency of the transmitter signal.
• increasing the amplitude of the absolute sensing transmitter signal increases the proximity sensing distance and accuracy.
• a capacitive sensing transmitter signal such as V Ab sinput of Figure 5 having a higher frequency may increase the avoidance of lower frequency interference components.
• an input device that is configured to operate with an absolute capacitance measurement transmitter signal such as V Ab sinput of Figure 5, having increased amplitude and/or frequency (as compared with conventional techniques for absolute capacitive sensing), may be configured to operate with a transmitter signal similar to that of a transcapacitive sensing device. Such embodiments allow for the interference
• an input device configured to operate in both a transcapacitive sensing mode and an absolute capacitive sensing mode may be referred to as a hybrid capacitive sensor device.
• the absolute capacitive sensing transmitter signal frequency may be at least equal to, if not faster than, that of a transcapacitive transmitter signal.
• the half sensing cycle for an absolute capacitive sensing method may be at least equal to, if not faster than, that of a
• a hybrid capacitive sensing device may be configured to operate in both a transcapacitive sensing mode and an absolute capacitive sensing mode.
• the hybrid capacitive sensing device is configured to switch between a transcapacitive sensing mode and an absolute capacitive sensing mode based on, but not limited to, an operating state of the input device, an input object event and a time delay.
• an absolute capacitive sensing mode may be used to detect the presence of an input object above, but not touching an input surface of an input device, and in response to detection of such an input object the input device may switch from an absolute capacitive sensing mode to a transcapacitive sensing mode.
• nput may be increased in comparison to the sensing frequency that is possible using conventional absolute capacitive sensing.
• the reference voltage (operating voltage) of the charge integrator of the capacitance measuring circuit coupled to the sensor electrode may be modulated.
• the reference voltage may be modulated symmetrically above and below a reference value.
• the frequency and/or amplitude of the modulation may be adjusted during operation, such as to avoid interference, prevent saturation, or adjust the dynamic range of an amplifier.
• the reference voltage may be modulated with signal that is similar to the transcapacitive sensing signal (e.g., V Tr ansinput) in waveform and/or frequency (for example a square wave with similar frequency).
• the reference voltage, V ref may be an attenuated version of the transcapacitive sensing signal.
• the reference voltage may be modulated based on a receiver module supply voltage.
• the reference voltage, V ref may be an attenuated version of the receiver module supply voltage, such as M2 V dd .
• the reference voltage may be variable.
• the reference voltage may be selected and configured to increase the dynamic range of the differential amplifier being used as a charge integrator.
• the reference voltage and the feedback capacitance may be selected to increase the dynamic range of the differential amplifier being used as a charge integrator.
• the differential amplifier being used as a charge integrator may be decoupled from the sensor electrode or electrodes which are being used for absolute capacitive sensing during a reset phase of the charge integrator. In one embodiment, decoupling the charge integrator from the sensor electrode during the reset phase provides a shorter reset phase for the charge integrator than would be experienced if it were to remain coupled to the sensor electrode during the reset phase.
• the same charge integrator may be configured to receive resulting signals while an input device operates in a transcapacitive sensing mode and an absolute capacitive sensing mode.
• the transcapacitive sensing mode and the absolute sensing mode may be configured to use similar transmitter signals (similar in at least one of frequency and amplitude).
• transmitter frequency and the sensing cycles for the transcapacitive sensing mode and the absolute sensing mode are configured to be substantially the same.
• the absolute capacitive sensing "pre-charge/reset" and "integrate" durations, when combined are substantially equal to the reset and integrate times for transcapacitive sensing.
• the following example embodiments describes various ways to provide an absolute capacitive sensing having a reduced sensing cycle and an increased transmitter signal frequency.
• FIGS 4A and 4B illustrate operation of a capacitance measurement circuit 400 through a first half cycle of absolute capacitive sensing, according to an embodiment.
• Capacitance measurement circuit 400 may be included as part of an input device 100 and/or a processing system 1 10.
• processing system 1 10 may supply input voltages for circuit 400 as well as control signals which operate switches in circuit 400 and/or select capacitors from a bank of selectable capacitors.
• capacitance measurement circuit 400 comprises a differential amplifier 401 with inverting and non-inverting inputs and an output.
• a first switch SW1 is coupled between the non- inverting input of differential amplifier 401 and a sensor electrode, such as sensor electrode 270-0, to which circuit 400 is coupled.
• Differential amplifier 401 is configured as a charge integrator and includes a feedback capacitance disposed between its output and its inverting input.
• the feedback capacitance is represented by capacitor, C F B, that is coupled on one side to the output of differential amplifier 401 and on its other side to a location between the inverting input of differential amplifier 401 and switch SW1 .
• capacitor C FB can be composed of one or more selectable capacitances that are selected from bank(s) of selectable capacitors.
• a second switch, SW2 is disposed in parallel with feedback capacitor C F B- Switch SW2 operates as a reset mechanism to discharge and reset capacitor C F B-
• capacitance CB represents a background capacitance (which may include capacitance contributed by an input object) between sensor electrode 270-0 and ground.
• Capacitance measurement circuit 400 performs an absolute sensing method having a reduced half sensing cycle (as compared to conventional absolute capacitive sensing cycles), where differential amplifier 401 is set up as a charge integrator and the reference voltage applied to the non-inverting input of differential amplifier 401 is modulated by substantially equal amounts above and below a reference voltage V ref .
• the reference voltage of the integrating amplifier is modulated with a similar signal to the transcapacitive transmitter signal.
• V ref is approximately one half of a supply voltage, VDD.
• the absolute capacitive sensing frequency may be increased by using the propensity of differential amplifier 401 to balance voltages on its inputs to drive a transmitter signal onto sensor electrode 270-0 which is equal to the modulated voltage applied on the non-inverting input.
• This method of driving is different than conventional absolute capacitive sensing which uses a transmitter that is separate from a charge integrator.
• FIG. 4A illustrates the reset phase of the first half sensing cycle.
• the feedback capacitor, C FB is discharged and V out follows the V inp reference voltage, V Abs in P ut, that is modulated onto the non-inverting input of differential amplifier 401.
• switch SW2 is closed and switch SW1 is opened; and the polarity of the modulation of V Abs i n put switches.
• the shift in reference voltage, V Abs i n put can occur at the very beginning of the reset phase or at some time after the reset phase has started.
• switch SW1 when switch SW1 is open, sensor electrode 270-1 is left to electrically float and thus substantially maintains whatever charge remained upon it.
• Closing switch SW2 causes capacitor C FB to discharge.
• the output and inverting input then take some time to settle to the new value of V Abs i np ut-
• the length of reset phase is predicated upon how long the settling and discharge take to occur.
• the discharge of C FB is fairly quick as there is no resistance in the path to slow it, and the reset time of differential amplifier 401 is hastened by opening SW1 to disconnect it from sensor electrode 270-0 so that it can more quickly settle without the capacitance of sensor electrode 270-0 coupled to its inverting input.
• FIG. 4B illustrates the integration phase of the first half sensing cycle.
• the integration phases are time periods where measurement takes place and may also be referred to as measurement phases.
• the non-inverting node of differential amplifier 401 continues to be driven to the same value of V Abs i np ut as during the reset phase shown in Figure 4A.
• C FB ⁇ s discharged and both inputs and the output of differential amplifier 401 have substantially settled at the voltage V Abs!nput being applied to the non-inverting input.
• switch SW1 is closed and switch SW2 is opened.
• FIG. 5 shows a comparison of diagrams of transcapacitive and new (as described herein) absolute capacitance sensing signals and modes (310 and 520 respectively), in accordance with various embodiments.
• Portion 310 is the same as portion 310 of Figure 3.
• Portion 520 illustrates a full absolute capacitive sensing cycle, according to embodiments described herein in Figures 4A, 4B, 6A-6D, and Figure 7.
• portion 520 illustrates transmitter and integrated resulting signals ⁇ V Abs in P ut and V OUT respectively) for an absolute capacitive sensing mode wherein 521 is the first half of a sensing cycle and 522 is the second half of a capacitive sensing cycle.
• Each half sensing cycle 521 or 522 includes both a pre-charge/reset phase, T Abs prechargeReset, and an integration phase, T Abs!negra te.
• the integration phases are time periods where measurement takes place and may also be referred to as measurement phases.
• the pre-charge/reset phase may include only reset (as illustrated in Figures 4A and 4B), some combination of reset and pre- charge (as illustrated in Figures 6A-6D), or only pre-charge as illustrated in Figure 7.
• absolute capacitive measurement is accomplished with a reduced half sensing cycle period (as compared to conventional techniques of absolute capacitive sensing illustrated in Figure 3).
• the pre-charge/reset phase is shown as being substantially the same length of time as the integration phase where measurement takes place, it should be appreciated that in some embodiments described herein the pre- charge/reset phase is shorter than the integration phase in a half sensing cycle such as 521 or 522. In some embodiments, for example, the pre-charge/reset phase may be an order of magnitude or more shorter than the integration phase in a half sensing cycle such as 521 or 522. Further, as can be seen from Figure 5, the reset phase is shorter than the pre-charge phase of Figure 3, providing a higher sensing frequency. It should also be noted that in some embodiments, the pre-charge/reset phase illustrated in Figure 5 is substantially equal to or shorter than the reset phase of transcapacitive sensing using the same sensor electrode.
• the reset phase during transcapacitive sensing may be 1/5, 1/10, or less of the transcapacitive integration phase
• this means that the pre-charge/reset phase illustrated in Figure 5 is substantially shorter than the conventional absolute sensing pre-charge phase illustrated in 320 of Figure 3.
• the combination of pre-charge/reset phase and integration phase in a half sensing cycle e.g., half sensing cycle 521 or 522 is substantially equal to or shorter than a half sensing cycle of transcapacitive sensing (e.g., 31 1 or 312) accomplished using the same sensor electrode.
• the absolute capacitive sensing transmitter signal which drives the sensor electrode can have a higher modulation amplitude than in the conventional technique for absolute capacitive sensing described in relation to Figure 3.
• Equation 1 the dynamic range of the output voltage is limited by the AV mf term.
• V out V ref ⁇ AV mf .
• the system may be affine, but not linear, in C B around V ref .
• Figures 6A-6D illustrate operation of an capacitive measurement circuit 600 through a full cycle of absolute capacitive sensing, according to an embodiment.
• Capacitance measurement circuit 600 may be included as part of an input device 100 and/or a processing system 1 10.
• processing system 1 10 may supply input voltages for circuit 600 as well as control signals which operate switches in circuit 600 and/or select capacitors from one or more banks of selectable capacitors.
• the feedback capacitance C FB0 of Figures 4A and 4B has been split into multiple portions, C FB0 and C FB i , so that one portion C FB0 can be reset while the other portion C FB1 is pre-charged to either 2 V mf or ground during the pre-charge/reset phase of a half sensing cycle.
• CFB1 is pre-charged to 2V ref or ground is accomplished by the positioning of switch SW3 during the pre-charge/reset phase of a half sensing cycle.
• the ratios of feedback capacitors C FB0 and C FB1 may be chosen to provide a charge integrator output, V out , which is a linear function of the background capacitance, C B , while maintaining the same sensing frequency increases as the method and circuit 400 shown in Figures 4A and 4B.
• V out charge integrator output
• the embodiment of Figures 6A-6D can also handle larger values of C B without saturating the receiver, increasing the dynamic range of the receiver.
• each of capacitors C FB0 and C FB1 may be composed of one or more selectable capacitors selected from banks of selectable capacitances.
• the total feedback capacitance is the sum of the capacitances of C FB o and CpB feedback capacitor C FB may be described as shown in Equation 2.
• the ratio of these two capacitors may be chosen as a function of the modulation amplitude, AV Kf , in order to substantially reduce the offset term of Equation 1.
• AV Kf modulation amplitude
• for each sensing cycle there are two half cycles, with each half cycle having a reset phase followed by an integration phase.
• the integration phases are time periods where measurement takes place and may also be referred to as measurement phases.
• switch SW1 is opened to decouple circuit 600 from sensor electrode 270-0; C FB o is discharged by closing switch SW2; the modulation of V Abs!nput on the non-inverting input of differential amplifier 401 is shifted to V mf + AV ref ; and C FB i is pre-charged with - ⁇ V ref + AV ref )C F Bi coulombs by coupling switch SW3 with a voltage of 2V Kf (which may be at or near V dd in some embodiments).
• the shift in reference voltage, V Abs!nput can occur at the very beginning of the reset phase or at some time after the reset phase has started.
• Switch SW2 operates as a reset mechanism to discharge and reset capacitor C FBO additionally, switch SW3 also operates as a reset mechanism by allowing capacitor C FBI to be pre- charged and reset to a selected value.
• switch SW1 when switch SW1 is open, sensor electrode 270-1 is left to electrically float and thus substantially maintains whatever charge remained upon it.
• reset phase 2 switch SW1 is opened to decouple circuit 600 from sensor electrode 270-0; CFBO is discharged by closing switch SW2; the modulation of V Abs input on the non-inverting input of differential amplifier 401 is shifted to V mf - AV mf ; and C FB i is pre-charged with (V ref + AVr ef )C F Bi coulombs by coupling switch SW3 with ground.
• C FB0 and C FB i are placed in parallel by coupling switch SW3 with the output of differential amplifier 401 and opening switch SW2; and the inverting input of differential amplifier 401 is connected to C B by closing switch SW1 .
• This causes the pre- charge stored on C FB i and any remaining charge to flow through C FB0 + C FB i to charge C B with 0 ⁇ ⁇ - AV ⁇ f ) coulombs.
• C FB i may be configured to increase the dynamic range of the receiver channel by acting as a charge subtractor which subtracts charge from CB, and thus presents a smaller signal from sensor electrode 270-0 for application by differential amplifier 401.
• C FB i may be configured to increase the range of C B that may be measured by the receiver channel of processing system 1 10 that is operating in absolute capacitance sensing mode.
• C FB1 may be configured to increase the range of the modulation of the reference voltage for the receiver channel.
• C FB1 may be configured to increase AV ref .
• the value of C FB0 may be selected to achieve different levels of interference rejection.
• the value of C FB0 may be selected to achieve different levels of gain (affecting signal to noise ratio (SNR), and sensitivity).
• the value of C FB i may be selected to achieve different levels of charge subtraction.
• the values of C FB0 and C FB i may be selected in concert with one another to achieve different levels of charge subtraction.
• the O uf from differential amplifier 401 may be given by Equation 3.
• Equation 4 The modulation amplitude, a, may then be defined as shown in Equation 4.
• AV ref aV ref where for some, 0 ⁇ a ⁇ 1 Equation 4
• Equation 5 Selection of a as shown in Equation 5 causes the last two terms of Equation 3 to cancel out and the output is therefore represented more simply, as shown in Equation 6. Equation 5
• Equation 5 The output, V oui , may be centered around V MF and linear in C B .
• Equation 5 can be used to determine the values for CFBO and CFBI- It should be appreciated that the simplification illustrated in Equation 5 is shown by way of example and not of limitation. That is to say, in other embodiments, the simplified case of Equation 5 does not have to hold, and Equation 3 is not simplified in the manner demonstrated by Equation 5.
• Figure 7 illustrates a capacitance measurement circuit 700, according to an embodiment.
• Figure 7 illustrates an alternative implementation for absolute capacitance sensing to the embodiments illustrated in Figures 6A-6D and 4A and 4B.
• FIG. 7 implementation of Figure 7 is similar to the methods described in relation to and depicted in Figures 6A-6D if C FB0 in those embodiments is set to a zero capacitance value or not included and C FB i is set to some non-zero value.
• the operation of circuit 700 is the same as the operation of circuit 600, except that switch SW2 and capacitor C FB o, and thus the entire C FB (composed only of C FB1 ) is pre-charged during both reset phase 1 and reset phase 2.
• SW3 operates as a reset mechanism by allowing capacitor CFB to be pre-charged and reset to a selected value.
• each half cycle has a reset phase followed by an integration phase.
• the integration phases are time periods where measurement takes place and may also be referred to as measurement phases.
• switch SW1 is opened to decouple circuit 400 from sensor electrode 270-1 ;
• C FB is pre-charged by coupling switch SW3 with a voltage 2Vref;
• the reference voltage, V Ab sinput, of differential amplifier 401 is shifted to V REF + A V MF .
• the shift in reference voltage, V Abs i nput can occur at the very beginning of the reset phase or at some time after the reset phase has started.
• switch SW1 when switch SW1 is open, sensor electrode 270-1 is left to electrically float and thus substantially maintains whatever charge remained upon it. Then during the integrate phase of the first half cycle: switch SW1 is closed to couple circuit 400 with sensor electrode 270-0; switch SW3 is coupled with the output of differential amplifier 401. These actions result in both C FB and C B being connected to the differential amplifier 401 during this integrate phase.
• the pre-charge stored on C FB charges C B with C B (V mf + AV ref ) coulombs.
• Equation 7 The integrator output, V out , for circuit 700 is given by Equation 7 at the end of the first cycle integrate and second cycle integrate phases, respectively.
• the integrator output is a linear function of C B while maintaining the same advantages as described above in relation to Figures 4A-6D.
• one or more techniques can also be employed to prevent inadvertent saturation of differential amplifier 401 by peak transients.
• one or more resistors can be added to attenuate peak transients on the inverting input to amplifier 401 to prevent charge loss through open switches and inadvertent saturation of amplifier 401 ; in some embodiments, the timing of the operation of switches SW1 and SW3 can be adjusted such that for example switch SW1 remains open during a transition from a reset phase to an integrate phase until after switch SW3 is moved from either 2Vref or Ground to being coupled with V out or else is switch SW1 is closed and then switch SW3 is repositioned from either 2V ref or Ground to being coupled with V out . In some embodiments a combination of one or more added resistors and alterations in the timing of the operation of switches SW1 and SW3 may be utilized.
• FIG. 8 illustrates a capacitance measurement circuit 400, according to some embodiments.
• circuit 400 of Figures 4A and 4B is illustrated in as being used as a charge integrator for transcapacitive sensing.
• a transmitter output, TXO of processing system 1 10 drives a first sensor electrode (e.g., transmitter electrode 260-0) with a transmitter signal, TX S IG- A transcapacitance C TRANS between transmitter electrode 260-0 and another sensor electrode (e.g., receiver electrode 270-0) couples a resulting signal from this transmitter signal into this other sensor electrode (e.g., receiver electrode 270-0).
• a transmitter output, TXO of processing system 1 10 drives a first sensor electrode (e.g., transmitter electrode 260-0) with a transmitter signal, TX S IG- A transcapacitance C TRANS between transmitter electrode 260-0 and another sensor electrode (e.g., receiver electrode 270-0) couples a resulting signal from this transmitter signal into this other sensor electrode (e.g., receiver electrode 270-0).
• circuits 600 and 700 may be operated in a similar manner to perform transcapacitive sensing as part of a hybrid capacitive sensing circuit.
• FIGS 9A-9C illustrate a flow diagram 900 of a method of capacitance measurement with a differential amplifier having an output and differential first and second input, according to various embodiments.
• flow diagram 900 reference will be made to components and operates illustrated in one or more of Figures 6A-6D, Figures 4A-4B, and Figure 7.
• a switch disposed between a sensor electrode and a second input of a differential amplifier is opened to initiate a reset phase where the sensor electrode and the differential amplifier are decoupled. This is illustrated and described in conjunction with circuits 400, 600, and 700 where switch SW1 is opened to decouple the inverting input of differential amplifier 401 from sensor electrode 270-0.
• a feedback capacitance is reset to a first level of charge, the feedback capacitance is disposed between the second input and the output of the differential amplifier.
• the resetting can comprise a reset of all or a portion of the feedback capacitance.
• This resetting is illustrated and described in conjunction with circuits 400 and 600 where switch SW2 in circuits 400 and 600 is closed to cause capacitive discharge and reset a capacitor (C re in circuit 400 or CpBo in circuit 600) to a fully discharged state.
• This resetting is also illustrated and described in conjunction with circuits 600 and 700 and reset phase 1 , where switch SW3 in circuits 600 and 700 is positioned to cause pre-charge of a capacitor ⁇ C FB in circuit 700 or CFBI in circuit 600) to a selected value.
• the switch is closed to initiate a measurement phase where the second input and the sensor electrode are coupled. This is illustrated and described in conjunction with circuits 400, 600, and 700 where switch SW1 is closed to couple the inverting input of differential amplifier 401 with sensor electrode 270-0 and to facilitate an integration phase where the background capacitance associated with sensor electrode 270-0 is integrated and thus measured.
• Procedure 930 includes procedures 932 and 934.
• the measurement phase comprises balancing charge between the sensor electrode and the feedback capacitance such that a sensor electrode voltage equals a voltage of the first input equals a voltage of the second input, and the sensor electrode is charged to a value proportional to its capacitance and the voltage of the second input.
• the second input also settles to the same value as the voltage driven on the first input (the non-inverting input) of differential amplifier 401.
• the first input (the non-inverting input of differential amplifier 401 ) is driven with a modulated reference voltage.
• the sensor electrode voltage is equal to the voltage of second input of amplifier 401 which is equal to the voltage applied to the first input of amplifier 401 ; and sensor electrode 270-0 is thus charged to a value proportional to its capacitance and the voltage of the first and second inputs.
• the measurement phase also comprises utilizing the differential amplifier to integrate charge on the sensor electrode, such that an absolute capacitance is measured.
• This absolute capacitance coupling is the sum of coupling between a sensor (e.g., sensor electrode 270-0) and an input object 140 (if present) and a coupling between the sensor (e.g., sensor electrode 270- 0) and GND plane.
• differential amplifier 401 integrates the charge, C B , present on sensor electrode 270-0.
• C B includes the background capacitance between the sensor electrode and ground, and if an input object 140 is present in the sensing region associated with sensor electrode 270-0 its capacitance will be part of this background capacitance which is integrated and measured.
• procedures 910-930 further comprises procedures 940 and 950.
• opening the switch after the measurement phase to initiate a second occurrence of the reset phase is split into two half cycles and each half cycle includes a reset phase.
• 910 describes the reset phase of the first half sensing cycle (e.g., 521 of Figure 5)
• 940 describes opening switch SW1 again to initiate the reset phase of the second half sensing cycle (e.g., 522 of Figure 5).
• the level of modulation of V Ab sinput may be switched, such as from V ref + AV mf to V ref - AV ref .
• the second reset phase involves resetting the feedback capacitance to a second level of charge, wherein the first and second levels of charge are different. With reference to Figure 6B and Figure 7, in one embodiment, this involves pre-charging all or a portion of a feedback capacitance to a different level of charge than during the first reset phase. This is accomplished by positioning of switch SW3. For, example if switch SW3 was coupled with 2 V ref during the first reset phase it would be coupled with ground during the second reset phase.
• the method as illustrated by procedures 910-930 further comprises procedure 960. At procedure 960 in one embodiment, during a transcapacitive sensing cycle, the differential amplifier is utilized to measure a resulting charge on the sensor electrode.
• the resulting charge corresponds to a capacitive coupling between the sensor electrode and a second sensor electrode, wherein the second sensor electrode has been driven with a transmitter signal.
• Figure 8 shows differential amplifier 401 being used to integrate a resulting charge/signal on receiver electrode 270-0, where that resulting charge results from transmitter electrode 260-0 being driven with a transmitter signal by processing system 1 10.
• a method of capacitance measurement with a differential amplifier having an output and differential first and second inputs comprising: opening a switch disposed between a sensor electrode and said second input of said differential amplifier to initiate a reset phase where said sensor electrode and said differential amplifier are decoupled; resetting a feedback capacitance to a first level of charge, said feedback capacitance disposed between said second input and said output; closing said switch to initiate a measurement phase where said second input and said sensor electrode are coupled, said measurement phase comprising; balancing charge between said sensor electrode and said feedback capacitance such that a sensor electrode voltage equals a voltage of said first input equals a voltage of said second input, and said sensor electrode is charged to a value proportional to its capacitance and said voltage of said second input; and utilizing said differential amplifier to integrate charge on said sensor electrode, such that an absolute capacitance is measured.
• a capacitance measurement circuit comprising: a differential amplifier comprising: differential first and second inputs; and an output; a switch coupled with said second input, said switch having a closed state and an open state, wherein said second input is coupled with a sensor electrode in a measurement phase when said switch is in said closed state, and wherein said second input is decoupled with said sensor electrode in a reset phase when said switch is in said open state; a feedback capacitance coupled between said output and said second input; a reset mechanism coupled in parallel with at least a portion of said feedback capacitance and configured to reset said feedback capacitance to a first level of charge during a first occurrence of said reset phase; and wherein during said measurement phase said differential amplifier operates to charge said sensor electrode while balancing voltages on said first and second inputs to a voltage level associated with a modulated reference voltage coupled with said first input and to integrate charge on said sensor electrode to measure capacitance corresponding to a coupling between said sensor electrode and an input object.
• An input device comprising: a first sensor electrode; a differential amplifier comprising: differential first and second inputs; and an output; a switch coupled with said second input, said switch having a closed state and an open state, wherein said second input is coupled with said first sensor electrode in a measurement phase when said switch is in said closed state, and wherein said second input is decoupled with said first sensor electrode in a reset phase when said switch is in said open state; a feedback capacitance coupled between said output and said second input; a reset mechanism coupled in parallel with at least a portion of said feedback capacitance and configured to reset said feedback capacitance to a first level of charge during a first occurrence of said reset phase; and wherein during said measurement phase said differential amplifier operates to charge said first sensor electrode while balancing voltages on said first and second inputs to a voltage level associated with a modulated reference voltage coupled with said first input and to integrate charge on said first sensor electrode to measure capacitance corresponding to a coupling between said sensor electrode and an input object.
• Concept 14 The input device of Concept 13, further comprising: a second sensor electrode; a transmitter coupled with said second sensor electrode and configured to drive a transmitter signal on said second sensor electrode; and wherein, during a transcapacitive sensing cycle of said input device, said differential amplifier is further configured to measure a resulting charge on said first sensor electrode corresponding to a capacitive coupling between said first and second sensor electrodes.

Landscapes

• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Theoretical Computer Science (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Human Computer Interaction (AREA)
• Electronic Switches (AREA)
• Measurement Of Resistance Or Impedance (AREA)

Priority Applications (3)

Applications Claiming Priority (6)

Publications (1)

Family

ID=49946027

Family Applications (1)

Country Status (5)

Cited By (4)

Families Citing this family (37)

Citations (5)

Family Cites Families (31)

• 2013
  • 2013-03-15 US US13/843,129 patent/US9182432B2/en active Active
  • 2013-07-12 WO PCT/US2013/050386 patent/WO2014014785A1/en not_active Ceased
  • 2013-07-12 CN CN201380047249.1A patent/CN104603728B/zh active Active
  • 2013-07-12 KR KR1020157001108A patent/KR101944151B1/ko active Active
  • 2013-07-12 JP JP2015523147A patent/JP6112494B2/ja active Active
• 2015
  • 2015-07-17 US US14/802,720 patent/US9958488B2/en active Active

Patent Citations (5)

Also Published As

Similar Documents

Legal Events