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 master-slave circuit is disclosed that maintains synchronization between two integrated circuit chips, using minimal chip resources. In one embodiment, a single, bidirectional communication path is shared by the two chips. Meanwhile, only one I/O port on each chip is used to send and receive signals via the bidirectional communication path. The first chip to detect a signal event is designated the master and controls the bidirectional communication path. The master can communicate the status to the other chip by controlling the logic state of the I/O ports. When the second chip detects that the I/O port is controlled by the first chip, the second chip will logically deduce that it is now the slave. If both chips detect the signal event at substantially the same time, one of the two chips is pre-programmed to assume control of the I/O port as the master.
Abstract:
An electronic device may include a first controller associated with some channels of a digitizer having channels configured to receive a signal from a stylus, and with each channel having a direction. A second controller may be associated with channels of the digitizer not associated with the first controller. The first controller may scan for the signal at each channel associated with the first controller, and based on acquisition of the signal at a given channel associated with the first controller, calculate a property of the signal. The first controller may send the calculated property and the direction of the given channel to the second controller. The first controller and the second controller may scan for the signal at each channel having the direction of the given channel, at acquisition intervals based upon the calculated property.
Abstract:
A current source includes a first current path including a first current mirror transistor and an input current source coupled in series, a second current path including a second current minor transistor, wherein control terminals of the first and second current minor transistors are connected, a first circuit configured to provide a controlled auxiliary current in the second current path, and a second circuit configured to provide a controlled output current in the second current path when or after the auxiliary current has reached steady state. The current source may include one or more cascode transistors in the first current path and one or more cascode transistors in the second current path. The first circuit may be activated before the second circuit is activated.
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 electronic device may include a first controller associated with some channels of a digitizer having channels configured to receive a signal from a stylus, and with each channel having a direction. A second controller may be associated with channels of the digitizer not associated with the first controller. The first controller may scan for the signal at each channel associated with the first controller, and based on acquisition of the signal at a given channel associated with the first controller, calculate a property of the signal. The first controller may send the calculated property and the direction of the given channel to the second controller. The first controller and the second controller may scan for the signal at each channel having the direction of the given channel, at acquisition intervals based upon the calculated property.
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:
A touch screen device having a touch screen panel and a method for operating a touch screen device are provided. The method includes monitoring, during a noise monitoring phase, channel signals of a first set of channels and a second set of channel of the touch screen panel, detecting a stylus signal in response to a channel signal greater than a stylus threshold and less than a palm threshold, selecting the first set of channels when the stylus signal is detected on at least one channel of the first set of channels and is not detected on the second set of channels, and selecting the second set of channels when the stylus signal is detected on at least one channel of the second set of channels and is not detected on the first set of channels.