Abstract:
A capacitive discharge circuit includes a line having a capacitance, a switched capacitor circuit including a capacitor, a switched circuit coupled to the line, and a voltage regulator coupled between the switched capacitor circuit and the switched circuit. A controller operates the switched capacitor circuit and switched circuit to in a first phase, charge the capacitor by coupling the capacitor between a common mode and a power supply, and in a second phase, discharge the capacitor by coupling the voltage regulator in series with the capacitor between the power supply node a ground. The controller is also configured to in a third phase, charge the capacitor by coupling the capacitor between the common mode and the power supply, and in a fourth phase, share charge between the line and the capacitor by coupling the voltage regulator and the capacitor in series between the line and the ground.
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:
A touch panel includes a plurality of drive lines, a plurality of orthogonal sense lines, and a plurality of sensors. A method of controlling the touch panel to detect touches includes simultaneously applying a drive signal to each of a group of drive lines of the touch panel. Each of the drive signals is applied to a corresponding drive line in the group during a time slot and all the applied drive signals having the same electrical characteristics over the time slot. The method includes sensing sense signals generated on the sense lines in response to the applied drive signals and processing the sense signals to detect touches of the touch panel.
Abstract:
A readout device for a capacitive sense matrix includes a computer readable storage medium configured to store capacitance data. The capacitance data represents capacitance values of the capacitive sense matrix. The readout device also includes a readout circuit configured to receive a signal from the capacitive sense matrix, the readout circuit being configured based upon the capacitance data. Also described are a readout method and a method of compensating for variations in capacitance.
Abstract:
Capacitance sensing circuits and methods are provided. A dual mode capacitance sensing circuit includes a capacitance-to-voltage converter having an amplifier and an integration capacitance coupled between an output and an inverting input of the amplifier, and a dual mode switching circuit responsive to mutual mode control signals for a controlling signal supplied from a capacitive touch matrix to the capacitance-to-voltage converter in a mutual capacitance sensing mode and responsive to self mode control signals for controlling signals supplied from the capacitive touch matrix to the capacitance-to-voltage converter in a self capacitance sensing mode, wherein the capacitance sensing circuit is configurable for operation in the mutual capacitance sensing mode or the self capacitance sensing mode.
Abstract:
A charge sensing circuit generates a voltage in a sensing period that is indicative of sensed charge. The generated voltages are accumulated by an accumulator circuit over a number of sensing periods. A noise detection circuit senses when the voltage generated by the charge sensing circuit is outside of a boundary and generates a detection signal in response thereto. A control circuit, in response to the detection signal, controls the accumulator circuit to block accumulation of the voltages generated by the charge sensing circuit during at least the sensing period in which the detection signal is generated. An analog-to-digital converter circuit then converts an accumulated output voltage from the accumulator circuit to a digital value at the end of an accumulation time period that includes the sensing periods. The end of the accumulation time period is delayed by at least one sensing period in response to the detection signal.
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 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:
In accordance with an embodiment, a method of operating a touch panel includes operating a slave touch panel controller by receiving a synchronization signal from a master touch panel controller of a display driver circuit, and polling a plurality of receive inputs coupled to outputs of an in-cell touch module based on an predetermined pattern.
Abstract:
Capacitance sensing circuits and methods are provided. The capacitance sensing circuit includes a capacitance-to-voltage converter configured to receive a signal from a capacitance to be sensed and to provide an output signal representative of the capacitance, an output chopper configured to convert the output signal of the capacitance-to-voltage converter to a sensed voltage representative of the capacitance to be sensed, an analog accumulator configured to accumulate sensed voltages during an accumulation period of NA sensing cycles and to provide an accumulated analog value, an amplifier configured to amplify the accumulated analog value, and an analog-to-digital converter configured to convert the amplified accumulated analog value to a digital value representative of the capacitance to be sensed. The analog accumulator may include a low pass filter having a frequency response to filter wideband noise.