Abstract: A circuit includes a force driver to apply a force signal to a force node associated with a mutual capacitance to be sensed, and a charge to voltage converter having an input coupled to receive a sense signal from a sense node associated with the mutual capacitance to be sensed. The charge to voltage converter includes an integrator circuit to integrate the sense signal to sense the mutual capacitance, an input switch between the input of the charge to voltage converter and an input of the integrator circuit, and a reset switch between an output of the integrator circuit and the input of the integrator circuit. A control circuit controls generation of the force signal to alternate between at least two different frequencies and generates, for each half cycle of the force signal, a first signal for closing the input switch and a second signal for closing the reset switch.

Abstract: A device includes a force driver applying a force signal to a force node associated with a mutual capacitance between the force node and a sense node. A sensing circuit receives a sense signal from the sense node associated with the mutual capacitance between the force node and the sense node, and generates an output indicative of the sensed mutual capacitance. A control circuit controls the generation of the force signal to alternate between at least two different frequencies by generating consecutive pulses, with a given pulse of the consecutive pulses at a first of the at least two different frequencies. In a first operating state, a next pulse immediately succeeding the given pulse is at a second of the at least two different frequencies, and in a second operating state the next pulse immediately succeeding the given pulse is at the first of the at least two different frequencies.

Abstract: A touch screen controller includes an input stage configured to receive and condition a touch output from a touch matrix to produce a touch signal. An accumulation stage is configured to receive the touch signal and accumulate the touch signal to produce an accumulated output. The accumulated output is digitized by an analog to digital converter to produce a touch strength value. A given amount of charge is subtracted from or added to accumulated output during a next accumulation if the touch strength value is greater than an upper threshold or less than a lower threshold. This avoids saturation of components in the touch screen controller and therefore increases the signal to noise ratio.

Abstract: A touch screen controller disclosed herein includes a circuit configured to generate a digital touch voltage comprises of samples, at a base sampling rate. The touch screen controller also includes a digital processing unit configured to analyze a first subset of samples of the digital touch voltage samples to determine noise content thereof, the first subset of samples corresponding to samples at a first investigated sampling rate that is a first function of the base sampling rate. The digital processing unit is also configured to analyze a second subset of samples of the digital touch voltage to determine noise content thereof, with the second subset of samples corresponding to samples at a second investigated sampling rate that is a second function of the base sampling rate, and determine a preferred sampling rate from among the first and second investigated sampling rates as a function of determined noise content thereof.

Abstract: A device includes a force driver applying a force signal to a force node associated with a mutual capacitance between the force node and a sense node. A sensing circuit receives a sense signal from the sense node associated with the mutual capacitance between the force node and the sense node, and generates an output indicative of the sensed mutual capacitance. A control circuit controls the generation of the force signal to alternate between at least two different frequencies by generating consecutive pulses, with a given pulse of the consecutive pulses at a first of the at least two different frequencies. In a first operating state, a next pulse immediately succeeding the given pulse is at a second of the at least two different frequencies, and in a second operating state the next pulse immediately succeeding the given pulse is at the first of the at least two different frequencies.

Abstract: A circuit includes a force driver to apply a force signal to a force node associated with a mutual capacitance to be sensed, and a charge to voltage converter having an input coupled to receive a sense signal from a sense node associated with the mutual capacitance to be sensed. The charge to voltage converter includes an integrator circuit to integrate the sense signal to sense the mutual capacitance, an input switch between the input of the charge to voltage converter and an input of the integrator circuit, and a reset switch between an output of the integrator circuit and the input of the integrator circuit. A control circuit controls generation of the force signal to alternate between at least two different frequencies and generates, for each half cycle of the force signal, a first signal for closing the input switch and a second signal for closing the reset switch.

Abstract: A circuit includes a force driver configured to apply a force signal to a force node associated with a mutual capacitance to be sensed. A sensing circuit receives a sense signal from a sense node associated with said mutual capacitance to be sensed. The sensing circuit operates to generate an output signal indicative of the sensed mutual capacitance. A control circuit controls generation of the force signal to alternate between at least two different frequencies and generate said output signal for each half cycle of the force signal.

Abstract: An electronic device includes a plurality of charge-to-current converters each including a first NMOS transistor having a source coupled to a sense line, a first capacitor between a gate and source of the first NMOS transistor so that a transient component of noise from the sense line is applied to both, a first PMOS transistor having a source coupled to the sense line, a second capacitor between a gate and source of the first PMOS transistor so the transient component of the noise is applied to both, a first current mirror having an input coupled to a drain of the first NMOS transistor and an output coupled to an output for that charge to current converter, and a second current mirror having an input coupled to a drain of the first PMOS transistor and an output coupled to the output for that charge to current converter.

Abstract: A touch screen controller includes an input stage configured to receive and condition a touch output from a touch matrix to produce a touch signal. An accumulation stage is configured to receive the touch signal and accumulate the touch signal to produce an accumulated output. The accumulated output is digitized by an analog to digital converter to produce a touch strength value. A given amount of charge is subtracted from or added to accumulated output during a next accumulation if the touch strength value is greater than an upper threshold or less than a lower threshold. This avoids saturation of components in the touch screen controller and therefore increases the signal to noise ratio.

Abstract: An electronic device includes a plurality of charge-to-current converters each including a first NMOS transistor having a source coupled to a sense line, a first capacitor between a gate and source of the first NMOS transistor so that a transient component of noise from the sense line is applied to both, a first PMOS transistor having a source coupled to the sense line, a second capacitor between a gate and source of the first PMOS transistor so the transient component of the noise is applied to both, a first current mirror having an input coupled to a drain of the first NMOS transistor and an output coupled to an output for that charge to current converter, and a second current mirror having an input coupled to a drain of the first PMOS transistor and an output coupled to the output for that charge to current converter.

Abstract: An electronic device disclosed herein includes a display layer generating display noise based on scanning thereof, and a sensing layer including a plurality of sense lines. A common voltage layer is coupled to the display layer and the sensing layer, with the common voltage layer capacitively coupling the display noise from the display layer to the each of the plurality of sense lines of the sensing layer via a different parasitic impedance. An amplitude of the display noise seen at an input to each sense line is a function of a location of that sense line. The electronic device includes a plurality of compensation impedances, with each compensation impedance coupled to a different one of the plurality of sense lines. Each of the plurality of compensation impedances has an impedance value such that an amplitude of the display noise at an output of each sense line is substantially equal.

Abstract: Disclosed herein is an electronic device including a sensing layer including a plurality of sense lines, and a plurality of single ended charge converter circuits each receiving input from a corresponding one of the plurality of sense lines. The electronic device also includes a plurality of current mirror circuits, each respectively mirroring output from one of the plurality of single ended charge converter circuits so as to produce two substantially identical outputs for each of the plurality of single ended charge converter circuits. There may be a plurality of subtractor circuits coupled to the plurality of current mirror circuits, with each of the plurality of subtractor circuits configured to output a voltage that is a function of a difference between outputs from two of the plurality of current mirror circuits associated with adjacent ones of the sense lines.

Abstract: A system and method for synchronizing two devices in communication with each other. When communication between the two devices is to be established, a synchronization process may be invoked. In an embodiment, a first device may initiate sending synchronization signals having rising edge and falling edge pairs. The second device may include a controller configured to receive the synchronization signals. However, noise may inhibit the ability of the controller to correctly receive and/or interpret the synchronization signals. Noise may cause detection components to falsely detect noise as a synchronization signal or may cause detection components to miss detection of an actual synchronization signal. A window generator may be used to generate comparison windows for the controller to detect synchronization signals.

Abstract: An active stylus is capacitively coupled to a capacitive touch panel for communication. The active stylus operates in a wait mode to receive initial communications from the panel. In response to such receipt, the active stylus synchronizes to a repeating communications frame implementing time division multiplexing. Communications from the active stylus to the panel include: information communications; synchronization communications and communications specific for columns and/or rows of the panel. Communications from the panel to the active stylus may be addressed uniquely to the stylus or commonly to a group of styluses.

Abstract: An electronic device includes a touch screen controller. The touch screen controller is configured to asynchronously measure a capacitance between a sense line and a drive line of a sensing layer with respect to a horizontal sync signal of a display layer. In addition, the touch screen controller is also configured to disconnect from the sense line for a given period of time following a rising edge of the horizontal sync signal so as to reduce capacitive coupling of display noise from the horizontal sync signal to the sensing layer.

Abstract: Disclosed herein is an electronic device including a display layer generating display noise based on scanning thereof and a sensing layer including a plurality of sense lines. The display noise is capacitively coupled from the display layer to each of the plurality of sense lines of the sensing layer. A differential charge converter circuit has first and second differential inputs respectively coupled to corresponding ones of the plurality of sense lines, and first and second reference inputs. The first and second reference inputs of the differential charge converter circuit are coupled to voltage references during a reset period, and are decoupled from the voltage references during a scan period.

Abstract: A system and method for synchronizing two devices in communication with each other. When communication between the two devices is to be established, a synchronization process may be invoked. In an embodiment, a first device may initiate sending synchronization signals having rising edge and falling edge pairs. The second device may include a controller configured to receive the synchronization signals. However, noise may inhibit the ability of the controller to correctly receive and/or interpret the synchronization signals. Noise may cause detection components to falsely detect noise as a synchronization signal or may cause detection components to miss detection of an actual synchronization signal. A window generator may be used to generate comparison windows for the controller to detect synchronization signals.

Abstract: Disclosed herein is an electronic device including a sensing layer including a plurality of sense lines, and a plurality of single ended charge converter circuits each receiving input from a corresponding one of the plurality of sense lines. The electronic device also includes a plurality of current mirror circuits, each respectively mirroring output from one of the plurality of single ended charge converter circuits so as to produce two substantially identical outputs for each of the plurality of single ended charge converter circuits. There may be a plurality of subtractor circuits coupled to the plurality of current mirror circuits, with each of the plurality of subtractor circuits configured to output a voltage that is a function of a difference between outputs from two of the plurality of current mirror circuits associated with adjacent ones of the sense lines.

Abstract: Disclosed herein is an electronic device including a display layer generating display noise based on scanning thereof and a sensing layer including a plurality of sense lines. The display noise is capacitively coupled from the display layer to each of the plurality of sense lines of the sensing layer. A differential charge converter circuit has first and second differential inputs respectively coupled to corresponding ones of the plurality of sense lines, and first and second reference inputs. The first and second reference inputs of the differential charge converter circuit are coupled to voltage references during a reset period, and are decoupled from the voltage references during a scan period.

Abstract: A touch screen controller disclosed herein includes a circuit configured to generate a digital touch voltage comprises of samples, at a base sampling rate. The touch screen controller also includes a digital processing unit configured to analyze a first subset of samples of the digital touch voltage samples to determine noise content thereof, the first subset of samples corresponding to samples at a first investigated sampling rate that is a first function of the base sampling rate. The digital processing unit is also configured to analyze a second subset of samples of the digital touch voltage to determine noise content thereof, with the second subset of samples corresponding to samples at a second investigated sampling rate that is a second function of the base sampling rate, and determine a preferred sampling rate from among the first and second investigated sampling rates as a function of determined noise content thereof.