Background capacitance compensation

Abstract

A processing system includes a sensor circuit and a baseline correction mechanism. The sensor circuit includes a receiver channel having an input configured to acquire a result signal from a sensor electrode. A background capacitance is formed between the sensor electrode and a conductive element. The baseline correction mechanism is coupled to the input of the receiver channel. The baseline correction mechanism includes a resistive element configured to be driven with a compensation signal to at least partially mitigate the background capacitance.

Description

[0001] Cross-references to related applications

[0002] This application claims the benefit of U.S. Provisional Patent Application Serial No. 62 / 889,407, filed August 20, 2019, which is hereby incorporated by reference. Technical Field

[0003] The disclosure herein generally relates to electronic devices, and more specifically to capacitive sensing devices. Background Technology

[0004] Input devices, including proximity sensor devices, can be used in a variety of electronic systems. A proximity sensor device may include a sensing area defined by a surface, wherein the proximity sensor device determines the presence, position, force, and / or motion of one or more input objects. Proximity sensor devices can be used to provide interfaces to electronic systems. For example, a proximity sensor device can be used as an input device for larger computing systems, such as a touchpad integrated into or surrounding a laptop or desktop computer. Proximity sensor devices can also be used in smaller computing systems, such as a touchscreen integrated into a cellular phone. Additionally, proximity sensor devices can be implemented as part of a car's multimedia information system. Summary of the Invention

[0005] In one embodiment, a processing system includes a sensor circuit and a first baseline correction mechanism. The sensor circuit includes a first receiver channel having an input configured to acquire a first result signal from a first sensor electrode. A first background capacitance is formed between the first sensor electrode and a conductive element. The first baseline correction mechanism is coupled to the input of the first receiver channel. The first baseline correction mechanism includes a first resistive element configured to be driven by a first compensation signal to at least partially reduce the first background capacitance.

[0006] In one embodiment, the input device includes a first sensor electrode, a conductive element, and a processing system. The processing system includes sensor circuitry and a first baseline correction mechanism. The sensor circuitry includes a first receiver channel having an input configured to acquire a first result signal from the first sensor electrode. A first background capacitance is formed between the first sensor electrode and the conductive element. The first baseline correction mechanism is coupled to the input of the first receiver channel. The first baseline correction mechanism includes a first resistive element configured to be driven by a first compensation signal to at least partially reduce the first background capacitance.

[0007] In one embodiment, a method for operating a sensing device includes driving, during a first period, a resistive element of a first baseline correction mechanism with a first compensation signal to mitigate background capacitance between a sensor electrode and a conductive element. The first baseline correction mechanism is coupled to an input of a receiver channel of a sensor circuit. The method further includes acquiring, during the first period, a result signal from the sensor electrode with the receiver channel, and determining, based on the result signal, position information for an input object. BRIEF DESCRIPTION OF DRAWINGS

[0008] So that the manner in which the above-recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, can be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only example embodiments and are therefore not to be considered limiting of the scope of the disclosure, as the disclosure can admit to other equally effective embodiments.

[0009] Figure 1 and Figure 2 An example input device is illustrated in accordance with one or more embodiments.

[0010] Figure 3 and Figure 4 A portion of an example input device is illustrated in accordance with one or more embodiments.

[0011] Figure 5 An example resistive element is illustrated in accordance with one or more embodiments.

[0012] Figure 6 and Figure 7 A portion of an example input device is illustrated in accordance with one or more embodiments.

[0013] Figure 8 is a flowchart of a method for performing capacitive sensing in accordance with one or more embodiments.

[0014] To facilitate the understanding of this disclosure, like reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one embodiment can be beneficially utilized on other embodiments without specific recitation below. The figures referred to herein are not intended to be drawn to scale. Moreover, for the purpose of clarity, elements or DETAILED DESCRIPTION

[0015] The following detailed description is merely exemplary in nature and is not intended to limit the disclosure or the application and uses of the disclosure. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding background, summary or the following detailed description.

[0016] The sensor electrodes of the sensing device are capacitively coupled to nearby conductive elements, generating a background capacitance. In some applications, the nearby conductive elements are display electrodes of a display device. The background capacitance increases the total capacitance of the sensor electrodes, thus limiting the ability of the sensor circuit to detect relatively small changes in capacitance caused by the presence of an input object. For example, the background capacitance can saturate the sensor circuit, rendering it unable to detect small changes in capacitance caused by an input object. The background capacitance can be mitigated by driving a compensation current onto the receiver channel. As described below, the compensation current is generated by driving a compensation resistor with a compensation voltage to mitigate the background capacitance. Mitigating the background capacitance reduces the amount of background capacitance affecting the sensor electrodes, thus increasing the ability of the sensor circuit to detect changes in capacitance caused by an input object.

[0017] Figure 1 An input device 100 configured to reduce capacitive coupling between sensor electrodes and display electrodes is illustrated. The input device 100 can be configured to provide input to an electronic system (not shown). Some non-limiting examples of an electronic system include a desktop computer, a laptop computer, a netbook computer, a tablet, a terminal, a kiosk, a cellular phone, an automotive multimedia information center, and an Internet of Things (IoT) device, among others.

[0018] The input device 100 includes a processing system 110 and sensor electrodes 105. The processing system 110 operates the sensor electrodes 105 to detect one or more input objects 140 in a sensing region of the input device 100. Examples of input objects 140 include fingers, styli, and stylus pens, as illustrated in FIG. 1. Figure 1 The sensing region of the input device 100 encompasses any space above, around, in, and / or near the input device 100 in which the input device 100 is able to detect input

[0019] The sensor electrodes 105 are coupled to the processing system 110 via a plurality of traces 106. Figure 1 The example pattern of sensor electrodes 105 illustrated in FIG. 1 includes sensor electrodes 105 arranged in a plurality of rows and a plurality of columns. It is contemplated that the sensor electrodes 105 can be arranged in other patterns, such as a polar array, a repeating pattern, a non-repeating pattern, a non-uniform array, or other suitable arrangement. The sensor electrodes 105 can have a shape of a circle, a rectangle, a diamond, a star, a square, a non-convex shape, a convex shape, a non-concave shape, a concave shape, or other suitable geometric shape.

[0020] The sensor electrodes 105 are provided in one or more layers. In one embodiment, the sensor electrodes 105 can be provided in a common layer. For example, the sensor electrodes 105 are provided on a first side of a common substrate. In other embodiments, the sensor electrodes 105 are provided in two or more layers. For example, a portion of the sensor electrodes 105 can be provided on a first layer, while another portion of the sensor electrodes can be provided on a second layer. The first and second layers can be provided on different sides of a common substrate, or on different substrates. Furthermore, one or more of the sensor electrodes 105 overlap at least another of the sensor electrodes 105.

[0021] The sensor electrodes 105 are constructed from a conductive material, such as a metal mesh, indium tin oxide (ITO), etc. Furthermore, the sensor electrodes 105 are ohmically insulated from one another. That is, one or more insulators separate and prevent the sensor electrodes from electrically shorting.

[0022] The processing system 110 is configured to operate the sensor electrodes 105 to detect one or more input objects 140 in the sensing region of the input device 100. The processing system 110 is located, in whole or in part, in one or more integrated circuit (IC) chips. For example, the processing system 110 can be provided entirely in a single IC chip. Alternatively, the processing system 110 can be provided in multiple IC chips.

[0023] The sensor circuit 112 is coupled to the sensor electrodes 105 via the wiring traces 106. The sensor circuit 112 is configured to drive the sensor electrodes 105 with a sensing signal to detect one or more input objects 140 in the sensing region of the input device 100. The sensing signal includes a transcapacitive sensing signal and / or an absolute capacitive sensing signal.

[0024] The sensor circuit 112 includes digital and / or analog circuitry. For example, the sensor circuit 112 includes transmitter (or driver) circuitry configured to drive the sensing signal onto the sensor electrodes 105 and receiver circuitry to receive a resulting signal from the sensor electrodes 105. The receiver circuitry includes one or more receiver channels. Each of the receiver channels includes analog and / or digital circuitry. For example, each of the receiver channels includes at least one or more of an operational amplifier, a sample and hold circuit, one or more filters, a digital-to-analog converter (DAC), and / or a demodulator, among others. The exemplary receiver channels are described in further detail below in FIGS. 6 and 7. Figure 3 、 4 , 6 and 7 illustrate exemplary receiver channels.

[0025] In one example, the sensor circuit 112 operates the sensor electrodes 105 for transcapacitive sensing by driving a first one or more of the sensor electrodes 105 with a transcapacitive sensing signal and receiving a result signal with a second one or more of the sensor electrodes 105. The sensor electrodes 105 operated for transcapacitive sensing detect changes in capacitive coupling between the sensor electrodes driven with the transcapacitive sensing signal and the sensor electrodes operated as receiver electrodes. The capacitive coupling can be reduced when an input object coupled to ground (e.g., the input object 140) is proximate to the sensor electrodes.

[0026] The transcapacitive sensing signal is a periodic or non-periodic signal that varies between two or more voltages. Further, the transcapacitive sensing signal has a frequency between 20 kHz and 1 MHz. In other embodiments, other frequencies can be utilized. For example, frequencies less than 20 kHz and greater than 1 MHz can be utilized. The transcapacitive sensing signal can have a peak-to-peak amplitude in a range of about 1 V to about 10 V. However, in other embodiments, the transcapacitive sensing signal can have other peak-to-peak amplitudes. Additionally, the transcapacitive sensing signal can have a square wave shape, a sine wave shape, a triangle wave shape, a trapezoidal wave shape, or a sawtooth wave shape, among others.

[0027] In some embodiments, operating the sensor electrodes 105 to receive the result signal includes holding the sensor electrodes 105 at a substantially constant voltage or modulating the sensor electrodes 105 relative to the transcapacitive sensing signal. The result signal includes an effect corresponding to one or more transcapacitive sensing signals and / or corresponding to one or more environmental interference sources (e.g., other electromagnetic signals).

[0028] The sensor circuit 112 additionally or alternatively operates the sensor electrodes 105 for absolute capacitive sensing by driving a first one or more of the sensor electrodes 105 with an absolute capacitive sensing signal and receiving a result signal with the driven sensor electrode(s). The sensor electrodes 105 operated for absolute capacitive sensing detect changes in capacitive coupling between the sensor electrodes driven with the absolute capacitive sensing signal and an input object (e.g., the input object 140). The capacitive coupling of the sensor electrodes 105 driven with the absolute capacitive sensing signal is altered when an input object coupled to ground (e.g., the input object 140) is proximate to the sensor electrodes.

[0029] The absolute capacitive sensing signal is a periodic or non-periodic signal that varies between two or more voltages. Further, the absolute capacitive sensing signal has a frequency between 20 kHz and 1 MHz. In other embodiments, other frequencies can be utilized. Additionally, the absolute capacitive sensing signal can have a square wave shape, a sine wave shape, a triangle wave shape, a trapezoidal wave shape, or a sawtooth wave shape, among others. The absolute capacitive sensing signal can have a peak-to-peak amplitude in a range of about 1 V to about 10 V. However, in other embodiments, the absolute capacitive sensing signal can have other peak-to-peak amplitudes. Driving the sensor electrodes 105 with the absolute capacitive sensing signal includes modulating the sensor electrodes 105.

[0030] The result signal received when performing absolute capacitive sensing includes effects corresponding to one or more absolute capacitive sensing signals and / or corresponding to one or more environmental interference sources (e.g., other electromagnetic signals). The absolute capacitive sensing signals can be the same as or different from the transcapacitive sensing signals used to perform transcapacitive sensing.

[0031] The determination module 116 receives the result signal from the sensor circuit 112 and processes the result signal to determine changes in capacitive coupling of the sensor electrodes 105. Processing the result signal includes removing baseline measurements from the result signal, filtering the result signal, performing hysteresis on the result signal, and combining the result signal, among others, to determine changes in capacitive coupling of the sensor electrodes 105. The determination module 116 utilizes the changes in capacitive coupling of the sensor electrodes 105 to determine position information for one or more input objects (e.g., the input object 140). For example, a capacitive image can be generated from measurements corresponding to changes in capacitive coupling of the sensor electrodes 105, and the determination module 116 determines position information for the input object 140 from the capacitive image. Additionally or alternatively, measurements of changes in capacitive coupling of the sensor electrodes 105 are compared to one or more thresholds.

[0032] The result signal for detecting changes in capacitive coupling is received during a capacitive frame. The capacitive frame can correspond to one or more capacitive images. Multiple capacitive images can be acquired over multiple time periods, and differences between the images are used to derive information about the input object 140 in the sensing region of the input device 100. For example, successive capacitive images acquired over successive time periods can be used to track the motion(s) of one or more input objects entering, leaving, and within the sensing region.

[0033] "Position information" as used herein broadly encompasses absolute position, relative position, velocity, acceleration, and other types of spatial information. Exemplary "zero-dimensional" position information includes near / far or contact / no contact information. Exemplary "one-dimensional" position information includes position along an axis. Exemplary "two-dimensional" position information includes motion in a plane. Exemplary "three-dimensional" position information includes instantaneous or average velocity in space. Further examples include other representations of spatial information. History data regarding one or more types of position information can also be determined and / or stored, including, for example, history data tracking position, motion, or instantaneous velocity over time.

[0034] The processing system 110 can additionally include a display driver 114. The display driver 114 is coupled to the display electrodes (e.g., the data lines 214 and / or the cathode electrodes 222) of the display device 200 (e.g., the display device 200 of FIG. 1). The display driver 114 drives display update signals (e.g., sub-pixel data signals and / or reference electrode signals) onto the display electrodes to update the sub-pixels of the display device. The display driver 114 includes a source driver having an amplifier circuit configured to drive the sub-pixel data signals onto the data lines. Further, the display driver 114 communicates control signals to the gate control circuit of the display device to control the driving of the gate lines (e.g., the gate lines 216) to control the selection of the sub-pixels of the display device. Figure 2 Figure 2 The display driver 114, the sensor circuit 112, and the determination module 116 can be part of a common IC chip. Alternatively, one or more of the display driver 114, the sensor circuit 112, and the determination module 116 can be part of a first IC chip, and a second one or more of the display driver 114, the sensor circuit 112, and the determination module 116 are part of a second IC chip. Figure 2

[0035] The display driver 114, the sensor circuit 112, and the determination module 116 can be part of a common IC chip. Alternatively, one or more of the display driver 114, the sensor circuit 112, and the determination module 116 can be part of a first IC chip, and a second one or more of the display driver 114, the sensor circuit 112, and the determination module 116 are part of a second IC chip.

[0036] As illustrated in FIG. 1, the sensor electrodes 105 are disposed above the display panel 210 of the display device 200. In the depicted example, the display panel 210 is an organic light-emitting diode (OLED) display panel. However, in other embodiments, the display panel 210 can be configured as other display types (e.g., liquid crystal display (LCD), etc.). The display panel 210 includes display electrodes that are driven to update the sub-pixel electrodes 218 of the display panel 210. The display electrodes include the data lines 214 and the gate lines 216. Additionally, the display electrodes can include emission control lines (not shown) configured to control the brightness of the sub-pixels of the display panel 210. Figure 2 Figure 2

[0037] ​​​​The data lines 214 are coupled to the display driver 114, and the gate lines 216 are coupled to a gate select circuit (not shown). Each of the sub-pixel electrodes 218 is coupled to one of the gate lines 216 and one of the data lines 214. Further, in one or more embodiments, each of the sub-pixel electrodes 218 is coupled to an emission control line. In embodiments where the display device 200 is an OLED display device, the sub-pixel electrodes 218 can be referred to as anode electrodes.

[0038] The data lines 214 and the gate lines 216 are disposed in a metal layer disposed on the substrate 212. The data lines 214 are disposed in a metal layer between the substrate 212 and the metal layer that includes the gate lines 216. Alternatively, the gate lines 216 are disposed in a metal layer between the substrate 212 and the data lines 214.

[0039] As described above, the display driver 114 drives sub-pixel data signals onto the data lines 214 to update the sub-pixel electrodes 218. Gate select signals and gate deselect signals are driven onto the gate lines 216 by the gate select circuit to select (activate) and deselect (deactivate) corresponding sub-pixel electrodes 218 for updating.

[0040] The display panel 210 additionally includes an organic material 220, a cathode electrode 222, a display layer 224, and an encapsulation layer 226. The cathode electrode 222 is a sheet of resistive material that overlaps the sub-pixel electrodes 218. The cathode electrode 222 is coupled to and driven by the display driver 114 to provide a low impedance reference voltage. In embodiments where the display panel 210 is an LCD panel, the cathode electrode 222 is replaced with a common voltage (Vcom) electrode layer. Further, the cathode electrode 222 (or Vcom electrode layer) can be referred to as a reference electrode layer.

[0041] The substrate 212 is a flexible substrate. Alternatively, the substrate 212 can be a rigid substrate. The display layer 224 includes one or more polarizers and / or color filter glass, among other things. As illustrated, the sensor electrode 105 is disposed on the encapsulation layer 226. In embodiments where the display device 200 includes a lens, the sensor electrode 105 can be disposed on the lens instead of the encapsulation layer 226. The lens can be disposed above the encapsulation layer 226 or included instead of the encapsulation layer 226.

[0042] The display driver 114 is configured to update the sub-pixel electrodes 218 during a display frame to update an image displayed on the display panel 210. The display frame can be updated or refreshed approximately every 16 ms, generating a display refresh rate of approximately 60 Hz. In other embodiments, other display refresh rates can be employed. For example, the display refresh rate can be 90 Hz, 120 Hz, 140 Hz, or higher.

[0043] Further referenceFigure 1 The sensor circuit 112 is configured to drive the sensor electrodes at a capacitive frame rate for capacitive sensing during a capacitive frame. In one embodiment, during each capacitive frame, each sensor electrode 105 is operated for absolute capacitive sensing. Further, each capacitive frame can include a plurality of periods during which different sensor electrodes 105 are operated for absolute capacitive sensing.

[0044] The "capacitive frame rate" (at which successive capacitive images are acquired) can be the same or different from the "display frame rate" (at which display images are updated). The capacitive frame rate is an integer multiple of the display frame rate. In other embodiments, the capacitive frame rate is a fractional multiple of the display frame rate. Further, the capacitive frame rate is any fraction or multiple of the display frame rate. For example, the capacitive frame rate can be a rational fraction of the display rate (e.g., 1 / 2, 2 / 3, 1, 3 / 2, 2). The display frame rate is varied while the capacitive frame rate remains constant. Alternatively, the display frame rate remains constant while the capacitive frame rate is increased or decreased. The capacitive frame rate can be unsynchronized with the display refresh rate, or the capacitive frame rate can be a non-rational fraction of the display rate to minimize interference "beat frequencies" between display updates and input sensing.

[0045] Capacitive sensing (or input sensing) and display updates can occur during at least partially overlapping periods. For example, the sensor circuit 112 is configured to operate the sensor electrodes 105 for capacitive sensing during periods that overlap with times at which the display driver 114 operates the gate lines 216 and the data lines 214 to update an image displayed by the display panel 210. For example, updating the display panel 210 and operating the sensor electrodes 105 for capacitive sensing can be asynchronous with one another. Further, updating the display panel 210 and operating the sensor electrodes 105 for capacitive sensing can be synchronized or unsynchronized with one another.

[0046] Alternatively or additionally, updating the display panel 210 and operating the sensor electrode 105 for capacitive sensing can occur during a non-overlapping period. For example, updating the display panel 210 can occur during a display update cycle, while operating the sensor electrode 105 for capacitive sensing can occur during a non-display update cycle. A non-display update cycle can be a blanking cycle that occurs between the last line of a display frame and the first line of a subsequent display frame (e.g., during a vertical blanking cycle). Furthermore, a non-display update cycle can occur between display line update cycles for two consecutive display lines of a display frame, and is at least as long as the display line update cycle in time. In such embodiments, a non-display update cycle can be referred to as a long horizontal blanking cycle or a long h-blanking cycle, wherein the blanking cycle occurs between two display line update cycles within a display frame and is at least as long as the display line update cycle.

[0047] As discussed above, since the sensor electrode 105 is disposed above the display panel 210, the display electrodes of the display panel 210 (e.g., cathode electrode 222, data line 214, and / or gate line 216) are undesirably capacitively coupled to the sensor electrode 105. This capacitive coupling can be referred to as background capacitance (e.g., Figure 3 The C shown b Furthermore, the capacitance of sensor electrode 105 is increased. Therefore, the high background capacitance difference limits the amount of change in capacitive coupling of sensor electrode 105 that the receiver channel of sensor circuit 112 can detect. However, driving a compensation current to the input of the receiver channel of sensor circuit 112 reduces the amount of background capacitance. Therefore, the compensation current driven to the input of the receiver channel increases the ability of the sensor circuit's receiver to detect changes in capacitive coupling caused by input object 140.

[0048] Figure 3 A portion of an input device 100 according to one or more embodiments is illustrated. A processing system 110 of the input device 100 is coupled to a sensor electrode 105a. The sensor electrode 105a is, for example, Figure 1 One of the plurality of sensor electrodes 105 illustrated herein. The processing system 110 includes a baseline correction mechanism 330 and a sensor circuit 112 having a receiver channel 312. Sensor electrode 105a is coupled to an input 313 of the receiver channel 312 of the sensor circuit 112. The receiver channel 312 acquires (receives) a result signal from sensor electrode 105a. The receiver channel 312 can acquire the result signal in response to sensor electrode 105a being modulated (or driven) using a sensing signal. The receiver channel 312 can modulate sensor electrode 105a using a sensing signal, or an external transmitter can modulate sensor electrode 105a using a sensing signal. Although... Figure 3Embodiments of the sensor circuit 112 depict a single receiver channel 312, but in other embodiments, the sensor circuit 112 includes more than one receiver channel 312. For example, the sensor circuit 112 includes a receiver channel for each sensor electrode 105 that operates during a common time period to perform capacitive sensing.

[0049] The result signal can correspond to an amount of charge driven on the sensor electrode 105a to drive the sensor electrode 105a to the voltage of the sense signal. A capacitance C f is formed between the input object 140 and the sensor electrode 105a. f Changing the capacitance of the sensor electrode 105a to free space changes the amount of charge driven on the sensor electrode 105a. Thus, by measuring the result signal, C f may be determined. Furthermore, as C f varies, the amount of charge driven on the sensor electrode 105a changes accordingly. C f may vary based on a distance (e.g., horizontal and / or vertical distance) between the sensor electrode 105a and the input object 140, a size of the input object 140, or both. For example, C f decreases as the distance between the input object 140 and the sensor electrode 105a increases, and increases as the distance between the input object 140 and the sensor electrode 105a decreases. Furthermore, C f varies based on a size, shape, and / or layout of the sensor electrode 105. For example, C f increases as a size of the input object 140 and / or a size of the sensor electrode 105a increases.

[0050] The background capacitance C b is formed between the sensor electrode 105a and one or more proximate conductive elements. For example, C b is formed between the sensor electrode 105a and one or more display electrodes of the display panel 210. For example, in embodiments employing an OLED display device, C b is formed between the sensor electrode 105a and the cathode electrode 222, one or more sub-pixel electrodes 218, one or more gate lines 216, and / or one or more data lines 214. In embodiments employing an LCD display device, C b is formed between a common voltage electrode, one or more sub-pixel electrodes, one or more gate lines, and / or one or more data lines of the LCD device. The capacitance value of C b may vary based on a distance between the sensor electrode 105a and the conductive element (e.g., display electrode or other conductive element). For example, the capacitance value C breduce.

[0051] C b a capacitance value greater than C f . For example, for an input object (e.g., input object 140) having a diameter of about 9 mm, C f may be about 0.5 pF, while C b may be about 500 pF. As such, C b may make it difficult to determine C f from the resulting signal. Furthermore, C b increases the capacitance of sensor electrode 105a, and in turn, the charge driven on sensor electrode 105a during capacitive sensing, which can cause the circuitry of receiver channel 312 to saturate and increase the power required to drive sensor electrode 105a.

[0052] Baseline correction mechanism 330 is coupled to input 313 of receiver channel 312 and is used to offset the effects of C b . For example, baseline correction mechanism 330 is used to offset at least a portion of the effects of C b so that the effects of C b are at least partially mitigated. Baseline correction mechanism 330 subtracts charge from input 313 of receiver channel 312 to mitigate the effects of C b on sensor electrode 105a. Mitigating C b reduces the total capacitance coupled to receiver channel 312. Furthermore, mitigating C b reduces the amount of charge driven on sensor electrode 105a to be less than the saturation voltage of receiver channel 312, thereby providing free space for accurate capacitive sensing of input object 140. Furthermore, mitigating C b increases the size of C f relative to C b , thereby making it easier for the sensor circuitry to measure the value of C f . With reference to Figure 4 , baseline correction mechanism 330 can be used to offset the effects of C b so that the amount of charge driven on sensor electrode 105a is less than the saturation voltage of operational amplifier 414 of receiver channel 312.

[0053] Baseline correction mechanism 330 includes one or more passive circuit components. For example, baseline correction mechanism 330 includes one or more resistive elements (e.g., resistive element 432 of Figure 4 ). Furthermore, baseline correction mechanism 330 can additionally include one or more capacitive elements (as described below with reference to Figure 7 ).

[0054] Different baseline correction mechanisms 330 can be coupled to the input of each receiver channel of the sensor circuit 112. Alternatively, a common baseline correction mechanism 330 can be coupled to the input of two or more receiver channels of the sensor circuit 112.

[0055] In various embodiments, the baseline correction mechanism 330 is driven by a compensation signal V comp drive. comp The compensation signal V comp may be a modulated signal similar to the sense signal (e.g., a modulated capacitive sense signal and / or a modulated absolute capacitive sense signal). comp The compensation signal V comp may be provided by a driver external to the processing system 110. comp The frequency of the compensation signal V comp may be within circuit tolerances of the frequency of the sense signal. In one particular example, the frequency of the compensation signal V comp may be ±5% of the frequency of the sense signal. In some embodiments, the frequency of the compensation signal V comp may be within circuit tolerances of the frequency of the sense signal. In one particular example, the frequency of the compensation signal V comp may be ±5% of the frequency of the sense signal. In some embodiments, the frequency of the compensation signal V comp may be the same as the frequency of the sense signal. comp may have a common waveform shape. For example, the sense signal and the compensation signal V comp may have a first waveform shape. Alternatively, the sense signal can have a first waveform shape, and the compensation signal V comp may have a second waveform shape different from the first waveform shape. In addition, the compensation signal V comp may have a peak-to-peak amplitude similar to a peak-to-peak amplitude of the sense signal. For example, the amplitude of the compensation signal V comp may be within circuit tolerances of the peak-to-peak amplitude of the sense signal. In one particular example, the peak-to-peak amplitude of the compensation signal V comp may be greater than or less than the amplitude of the sense signal. For example, the peak-to-peak amplitude of the compensation signal V comp may be a multiple of the peak-to-peak amplitude of the sense signal. For example, the compensation signal V comp is M times the peak-to-peak amplitude of the sense signal, where M is greater than 1. In addition, as described in further detail below, the phase of the compensation signal V comp is different from the phase of the sense signal.

[0056] Figure 4A portion of an input device 400 is illustrated in accordance with one or more embodiments. The input device 400 includes a processing system 410 and a sensor electrode 105a. The processing system 410 is configured similarly to the processing system 110 and can replace the processing system 110 in the input device 100. The processing system 410 includes a baseline correction mechanism 430 and a receiver channel 412 of a sensor circuit (e.g., the sensor circuit 112). The receiver channel 412 includes an input 413, an operational amplifier 414, and a feedback capacitor C fb . The input 413 corresponds to the inverting input of the operational amplifier 414. A sense signal V tx is driven onto the non-inverting input of the operational amplifier such that the sensor electrode 105a is modulated. The operational amplifier 414 is configured to output a resulting signal V out . V out corresponds to the amount of charge driven onto the sensor electrode 105a when driven with V tx . When the input object 140 and / or the conductive element is proximate to the sensor electrode 105a, V out includes the effects of C f and C b .

[0057] The baseline correction mechanism 430 includes a resistive element 432 driven by V comp . The resistive element 432 can be a variable resistive element having a variable resistance. The variable resistance can be provided by one or more variable resistors or a resistor ladder used as a resistor digital-to-analog converter (R-DAC). In one embodiment, the resistive element 432 is a 10-bit R-DAC as illustrated in FIG. 6B. In other embodiments, the resistive element 432 can be an R-DAC that is less than a 10-bit R-DAC or more than a 10-bit R-DAC. Figure 5

[0058] The resistive element 432 has a resistance in a range of about 1000 ohms to about 5000 ohms. Alternatively, the resistance of the resistive element 432 can be less than about 1000 ohms or more than about 5000 ohms.

[0059] One or more of the phase of V comp , the frequency of V comp , and the resistance value of the resistive element 432 are selected to compensate for C b . C f is measured when C b is zero (e.g., there is no input object 140 within the sensing region of the input device 100), and the frequency of V comp and / or the resistance value of the resistive element 432 are adjusted to offset (e.g., mitigate) the effects of C out within V b . For example, V​comp The frequency and / or the resistance value of the resistive element 432, until C f When V is zero out Until it reaches a value of zero. Alternatively, V can be adjusted. comp The frequency and / or the resistance value of the resistive element 432, up to V out The threshold value is less than the threshold value. The threshold value is greater than 0 and less than the saturation voltage of operational amplifier 414. C b Can replace or be excluded from observing V out In addition to measurement, it can also be modeled. In such an embodiment, based on C... b The modeling value is used to select V comp The frequency and / or the resistance value of the resistive element 432. In a specific example, to compensate for approximately 500pF of C b V comp It has a frequency of approximately 200 kHz, and the resistance of the resistive element 432 is approximately 1600 ohms. However, in other embodiments, V comp The frequency can be less than or greater than about 200kHz, and the resistance value of the resistor element 432 can be greater than or less than about 1600 ohms.

[0060] V comp phase and V tx The phases are different. This is different from the phase of the sensed signal V. tx In comparison, V comp Phase delayed. V comp The phase can be related to the sensing signal V tx Their phases are opposite. For example, based on V tx Instead of V comp (For example, undriven V) comp The generated V out It has a first phase, while based on V comp Instead of V tx (For example, undriven V) tx The generated V out It has a second phase that is opposite to the first phase. The sensed signal V can be measured via receiver channel 412. tx The phase. Alternatively, the sensing signal V tx The phase is a parameter stored in the processing system 410 and is used to generate V. comp The phase.

[0061] For ease of explanation, the following example is based on a sensor electrode with an idealized resistor-capacitor model. However, the proposed concept can be applied to sensor electrodes with more complex resistor-capacitor models. V is defined based on the following equation. compthe phase, frequency, and / or peak-to-peak amplitude of the voltage across the resistor element 432.

[0062] V out is defined as:

[0063] Equation 1

[0064] C fb is the capacitance of the feedback capacitor 416 of the receiver channel 412. To compensate for the effect of V out in C b , such that C f V out = 0 when V comp can be derived according to the following parameters:

[0065] , or

[0066] Equation 2

[0067] In Equation 2, R comp is the resistance value of the resistor element 432. When A comp is defined as V comp will be simplified to:

[0068] Equation 3

[0069] where is determined according to

[0070] In various embodiments, the value of C fb is set to mitigate the effect due to interference coupled into the input device 400 through the input object 140. For example, the value of C fb is about 30 pF. In other embodiments, C fb may be greater than about 30 pF or less than about 30 pF.

[0071] ​The resistance element 432 can be configured to compensate for changes (e.g., increases and decreases) in operating temperature. For example, the resistance element 432 can include a first resistor having a resistance that increases in response to an increase in temperature and a second resistor having a resistance that decreases in response to an increase in temperature. The resistance element 432 can include more than two resistors having variable resistances in response to temperature changes. Two or more of the resistors can have similar variable resistances in response to temperature changes, and at least one of the resistors has a different variable resistance in response to temperature changes. For example, two or more resistors increase in resistance in response to temperature changes, and one or more resistors decrease in resistance in response to temperature changes. The resistors are coupled in series and increase or decrease the resistance of the resistance element 432 in response to temperature changes (e.g., increases or decreases) such that operation of the baseline correction mechanism 430 does not significantly alter in response to temperature changes. For example, the baseline correction mechanism 430 compensates for a change in the amount of C b of about ten percent.

[0072] Figure 5 A resistance element 532 is illustrated in accordance with one or more embodiments. As illustrated, the resistance element 532 is a 10-bit R-DAC. For example, the resistance element 532 can be a resistor ladder having 10 steps (e.g., steps b0-b9). In other embodiments, the resistance element 532 can be an R-DAC having more or less than 10 bits. The resistance values of each of the resistors in the resistance element 532 can be different. The resistance values of the resistance element can range from about 3 kilo-ohms to about 15 kilo-ohms. However, in other embodiments, resistance values less than about 3 kilo-ohms and / or greater than about 15 kilo-ohms can be utilized. In one embodiment, the resistance values of the resistors from resistor R0 to resistor R9 increase. The resistance of the resistance element 532 is selected by closing one or more of the switches coupled to the resistors R0-R9 and opening the other switches. For example, the resistance value of resistor R9 is selected by closing the switch coupled to resistor R9 and opening the other switches. As described above, one or more of the resistors R0-R9 can be implemented with multiple resistors that compensate for temperature changes. Figure 4 The resistance element 432 can be implemented as the resistance element 532.

[0073] Figure 6 A portion of an input device 600 is illustrated in accordance with one or more embodiments. The input device 600 includes a processing system 610 and a sensor electrode 105a. The processing system 610 is configured similarly to the processing system 110 and can replace the processing system 110 in the input device 100. The processing system 610 includes the baseline correction mechanism 430 and a receiver channel 612 of the sensor circuit (e.g., the sensor circuit 112). As described above with respect to the input device 100, the baseline correction mechanism 430 is configured to compensate for changes in the amount of CFigure 4 Compared to receiver channel 412, Figure 6 Receiver channel 612 includes a resistor R fb A feedback resistor 613 is used in place of a feedback capacitor 416. By using a feedback resistor 613 instead of a feedback capacitor 416, the circuit size of the receiver channel 412 is reduced compared to the circuit size of the receiver channel 412. The feedback resistor 613 is coupled between the output of the operational amplifier 414 and the inverting input of the operational amplifier 414. fb It is approximately 26.5 kiloohms. Alternatively, R... fb Less than or greater than approximately 26.5 kiloohms.

[0074] Figure 7 A portion of an input device 700 according to one or more embodiments is illustrated. The input device 700 includes a processing system 710 and sensor electrodes 105a. The processing system 710 is configured similarly to processing system 110 and may replace processing system 110 in input device 100. The processing system 710 includes a baseline correction mechanism 730 and a receiver channel 412 for sensor circuitry (e.g., sensor circuitry 112). The baseline correction mechanism 730 includes a capacitive element 732, and the baseline correction mechanism 730 is powered by V. comp2 Drive. V comp2 Provided by a driver of the processing system 710 or a driver external to the processing system 710.

[0075] The baseline correction mechanism 730 is coupled to input 413 of receiver channel 412. comp2 The frequency, peak-to-peak amplitude, and / or phase can be related to V comp The frequency, peak-to-peak amplitude, and / or phase are the same. Alternatively, V comp2 The frequency, amplitude, and / or phase can be related to V comp The frequencies, amplitudes, and / or phases are different. For example, V comp2 The phase can be related to V comp The phases are different. In one embodiment, V comp And baseline correction mechanism 430 provides a ratio to V comp2 A larger baseline compensation amount than that provided by the baseline correction mechanism 730. For example, by V comp The compensation current provided by the baseline correction mechanism 430 is greater than that provided by V comp2 The compensation current provided by the baseline correction mechanism 730.

[0076] Capacitive element 732 is a non-variable or variable capacitive element. For example, capacitive element 732 can include a capacitive DAC (C-DAC) that includes two or more capacitors and corresponding switches that select the capacitors to generate a capacitance value of capacitive element 732. The C-DAC can be a 4-bit C-DAC. However, in other embodiments, the C-DAC can be a greater than 4-bit C-DAC or a less than 4-bit C-DAC. The capacitance value of capacitive element 732 is approximately 4 pF. Alternatively, capacitive element 732 can be less than approximately 4 pF or greater than approximately 4 pF. Capacitive element 732 includes a range of capacitance values. For example, capacitive element 732 includes a range of capacitance values from approximately 1 pF to approximately 5 pF. Alternatively, the range of capacitance values of capacitive element 732 can include capacitance values less than 1 pF and / or greater than approximately 5 pF.

[0077] Baseline correction mechanism 430 can offset a first amount of background capacitance (e.g., mitigate a first portion of background capacitance C b ) and baseline correction mechanism 730 can offset a second amount of background capacitance (e.g., mitigate a second portion of background capacitance C b ). Baseline correction mechanism 430 mitigates a greater portion of background capacitance C b than baseline correction mechanism 730. Baseline correction mechanism 430 offsets a greater amount of background capacitance than the amount offset by second baseline correction mechanism 730.

[0078] Baseline correction mechanism 430 and baseline correction mechanism 730 can be driven simultaneously by V comp and V comp2 to offset background capacitance C b . Alternatively, baseline correction mechanism 430 can be driven by V comp during a first period and baseline correction mechanism 730 can be driven by V comp2 during a second period that does not overlap the first period.

[0079] Figure 8 FIG. 8 illustrates a method 800 for operating an input device, in accordance with one or more embodiments. At block 810, a baseline correction mechanism (e.g., 330 or 430) is driven with V comp to mitigate at least a portion of background capacitance C b of sensor electrode 105a during a first period. Background capacitance C bThe proximate conductive elements can be display electrodes (e.g., data lines 214, gate lines 216, sub-pixel electrodes 218, and / or cathode electrodes 222) of a display panel (e.g., display panel 210). The resistance of the resistive elements (e.g., resistive elements 432) of the baseline correction mechanism (e.g., baseline correction mechanism 430) can be adjusted to mitigate background capacitance C b For example, the resistance of the resistive elements can be increased or decreased to mitigate different amounts of background capacitance C b Alternatively, as at block 810, the baseline correction mechanism 730 can be driven by V comp2 For example, the baseline correction mechanism 730 is driven by V comp2 during a first period, which at least partially overlaps with a second period during which the baseline correction mechanism 330 or 430 is driven with V comp1 The first period and the second period are similar in length. Alternatively, the first period is shorter or longer than the second period. Further, the first period starts before or after the second period. Additionally or alternatively, the first period ends before or after the second period. In one example, the baseline correction mechanism 730 is driven by V comp2 and the baseline correction mechanism 330 or 430 is driven with V comp1 simultaneously with each other.

[0080] At block 820, a result signal is acquired by the sensor circuit 112. The result signal is acquired during a first period that at least partially overlaps with a period during which the background correction mechanism is driven with V comp The sensor electrode 105a is modulated by a receiver channel (e.g., receiver channel 312, 412, or 612) of the sensor circuit 112 to acquire the result signal. The result signal includes an effect corresponding to the background capacitance C b and the capacitance C f formed between the input object 140 and the sensor electrode 105a.

[0081] At block 830, the determination module 116 determines location information for the input object 140 from the result signal. For example, the determination module 116 receives the result signal from the sensor circuit 112 and processes the result signal to determine a change in capacitive coupling of the sensor electrode 105a. The determination module 116 utilizes the change in capacitive coupling of the sensor electrode 105a to determine a measurement of the change in capacitive coupling of the sensor electrode 105a and determines the location information for the input object 140 from the measurement of the change in capacitive coupling of the sensor electrode 105a.

[0082] Accordingly, the embodiments and examples set forth herein are presented by way of illustration and example for the best mode contemplated for carrying out the embodiments according to the technology and its specific application to thereby enable those skilled in the art to make and use the disclosure. However, various modifications and alterations to this description will be readily apparent to those skilled in the art, and the principles disclosed herein can be applied to other embodiments without departing from the scope of the disclosure. As set forth above, the descriptions are not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. Rather, the descriptions are intended to present the possible embodiments of the technology so as to enable any person skilled in the art to make and use the disclosure.

[0083] Reference Signs

[0084] 100 input device

[0085] 105 sensor electrode

[0086] 105a sensor electrode

[0087] 106 trace

[0088] 110 processing system

[0089] 112 sensor circuit

[0090] 114 display driver

[0091] 116 determination module

[0092] 140 input object

[0093] 200 display device

[0094] 210 display panel

[0095] 212 substrate

[0096] 214 data line

[0097] 216 gate line

[0098] 218 update sub-pixel electrode

[0099] 220 organic material

[0100] 222 cathode electrode

[0101] 224 display layer

[0102] 226 encapsulation layer

[0103] 312 receiver channel

[0104] 313 input

[0105] 330 baseline correction mechanism

[0106] 400 input device

[0107] 410 processing system

[0108] 412 receiver channel

[0109] 413 input

[0110] 414 operational amplifier

[0111] 416 feedback capacitor

[0112] 430 baseline correction mechanism

[0113] 432 resistive element

[0114] 532 resistive element

[0115] 600 input device

[0116] 610 processing system

[0117] 612 receiver channel

[0118] 613 feedback resistor

[0119] 700 input device

[0120] 710 processing system

[0121] 730 baseline correction mechanism

[0122] 732 capacitive element

[0123] 800 method

[0124] 810 block

[0125] 820 block

[0126] 830 block

Claims

1. A processing system comprising: a sensor circuit comprising a first receiver channel coupled to a first sensor electrode and having an input configured to acquire a first result signal from the first sensor electrode, wherein a first background capacitance is formed between the first sensor electrode and a conductive element, and wherein the sensor circuit modulates the first sensor electrode with a sense signal to acquire the first result signal; and a first baseline correction mechanism coupled to the input of the first receiver channel, the first baseline correction mechanism comprising a first resistive element configured to be driven with a first compensation signal to mitigate a first amount of the first background capacitance; a second baseline correction mechanism coupled to the input of the first receiver channel, the second baseline correction mechanism comprising a capacitive element, the first resistive element configured to be driven with a second compensation signal to mitigate a second amount of the first background capacitance, wherein the first and second compensation signals are different in phase from the sense signal.

2. The processing system of claim 1, wherein the first and / or second compensation signals are equal in frequency to the sense signal.

3. The processing system of claim 1, wherein the first resistive element is a variable resistive element.

4. The processing system of claim 3, wherein the variable resistive element comprises a resistor ladder having a plurality of selectable resistors.

5. The processing system of claim 1, wherein the sensor circuit further comprises a second receiver channel configured to acquire a second result signal from a second sensor electrode, and wherein the processing system further comprises a third baseline correction mechanism coupled to an input of the second receiver channel.

6. The processing system of claim 1, wherein the first receiver channel comprises an integrator and a feedback resistor coupled between an output of the integrator and an inverting input of the integrator.

7. An input device comprising: a first sensor electrode; a conductive element; and a processing system comprising: a sensor circuit comprising a first receiver channel coupled to the first sensor electrode and having an input configured to acquire a first result signal from the first sensor electrode, wherein a first background capacitance is formed between the first sensor electrode and the conductive element, and wherein the sensor circuit modulates the first sensor electrode with a sense signal to acquire the first result; and a first baseline correction mechanism coupled to the input of the first receiver channel, the first baseline correction mechanism comprising a first resistive element configured to be driven with a first compensation signal to mitigate a first amount of the first background capacitance; a second baseline correction mechanism coupled to the input of the first receiver channel, the second baseline correction mechanism comprising a capacitive element, the first resistive element configured to be driven with a second compensation signal to mitigate a second amount of the first background capacitance, ​ ​ wherein a phase of the first compensation signal and the second compensation signal is different from a phase of the sense signal.

8. The input device of claim 7, wherein a frequency of the first compensation signal and / or the second compensation signal is equal to a frequency of the sense signal.

9. The input device of claim 7, wherein the first resistive element is a variable resistive element.

10. The input device of claim 9, wherein the variable resistive element comprises a resistor ladder having a plurality of selectable resistors.

11. The input device of claim 7, further comprising a second sensor electrode, wherein the sensor circuit further comprises a second receiver channel configured to acquire a second result signal from the second sensor electrode, and wherein the processing system further comprises a third baseline correction mechanism coupled to an input of the second receiver channel.

12. A method for operating a sensing device, the method comprising: driving, during a first period, a resistive element of a first baseline correction mechanism with a first compensation signal to mitigate a first amount of background capacitance between a sensor electrode and a conductive element, the first baseline correction mechanism coupled to an input of a receiver channel of a sensor circuit, wherein the receiver channel is coupled to the sensor electrode; driving, during the first period, a capacitive element of a second baseline correction mechanism with a second compensation signal to mitigate a second amount of background capacitance, the second baseline correction mechanism coupled to the input of the receiver channel; modulating, during the first period, the sensor electrode with a sense signal, wherein a phase of the first compensation signal and the second compensation signal is different from a phase of the sense signal; acquiring, during the first period, a result signal from the sensor electrode with the receiver channel; and determining, based on the result signal, position information for an input object.

13. The method of claim 12, wherein the first compensation signal and / or the second compensation signal is equal to a frequency of the sense signal.

14. The method of claim 12, wherein the resistive element is a variable resistive element.

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