Abstract:
A video display includes a video display panel and a video display drive circuit configured to control a display on condition. A touch screen includes a touch screen panel (mounted on top of the video display panel) and a touch panel control and sense circuit configured to operate the touch screen panel in a self-capacitance mode. The touch panel control and sense circuit includes sense drive circuits configured to generate sense drive signals for application to sense lines of the touch screen panel. A controller controls actuation of the sense drive circuits so that the sense drive signals are synchronized to the display on condition. In an implementation, the leading edges of the sense drive signals are synchronized to the display on condition. In another implementation, a window is synchronized to the display on condition and the leading edges of the sense drive signals exhibit jitter within the window.
Abstract:
Disclosed is keypad circuitry operable to detect a pressed key while reducing electromagnetic interference (EMI). The keypad circuitry is operable to reduce EMI in two ways: a) reducing the voltage swing occurring at the row circuitry and column circuitry of the keypad, and b) reducing the number of signal transitions by restricting the signal transitions to occurring at the column and row corresponding to a pressed key. By limiting signal transitions to occurring only at the row and column corresponding to a pressed key, fewer signal transitions occur, and thus, less EMI is produced. Additionally, reduced voltage swings at the row circuitry and column circuitry results in reduced EMI.
Abstract:
A touch controller includes a touch frame processing (TFP) component that receives sensor signals containing information about a touch point on a touch screen. The TFP component processes the sensor signals to generate touch information associated with each touch point. The touch information includes a location and the association of one of a touch-in, touch-out, and touch-motion event. A touch coordinate processing (TCP) component receives touch information from the TFP component and determines whether to report the touch information associated with a current touch point. The TCP component determines a difference between the location of the current touch point and a previously detected touch point and assigns a motion status to each touch event and reports the touch information when the difference is greater than a motion tolerance and when less than the motion tolerance selectively blocks or reports the touch information as a function of the corresponding motion status.
Abstract:
An integrated temperature sensor provides an output current proportional to temperature rising from a zero value at a selectable reference temperature. The reference temperature can be selected by varying resistive values in the sensor's circuit. The temperature sensor can be manufactured at low cost and fully integrated on a chip using CMOS technology, and may be used for low-power applications.
Abstract:
A method comprises during a frame period finding a first EFT noise influenced sensor of a touch screen panel, determining whether the first EFT noise influenced sensor is located at a last transmitting/driving line of the touch screen panel, designating the frame period as a noise influenced frame period using an absolute value threshold if the first EFT noise influenced sensor is not located at the last transmitting/driving line and designating the frame period as the noise influenced frame period using a percentage threshold if the first EFT noise influenced sensor is located at the last transmitting/driving line.
Abstract:
A touch screen device is configured with rows of conductors capable of receiving wireless signals from a stylus. When the stylus touches the touch screen, the stylus emits multiple wireless signals in different directions. The conductors receiving the emitted wireless signals provide the signals to circuitry that filters, amplifies, and digitizes the wireless signals, as received at each conductor. The magnitude of each conductor's received wireless signal is computed, and the computed magnitudes are used to determine the location of the stylus on the touch screen surface. The stylus is assumed to be closer to conductors receiving stronger signals than those receiving weaker signals.
Abstract:
Circuitry is described for compensating leakage currents in capacitive sensing circuits. A single active leakage compensation circuit may sense a representative leakage current and drive a plurality of output transistors, each of which provides a compensating current to a respective capacitive sensing circuit. The leakage compensation circuit may sense current flow through a device substantially equivalent to a device exhibiting leakage current in a capacitive sensing circuit, and in response, provide a signal to drive one or more output transistors to supply approximately equivalent currents to a plurality of circuit nodes. For embodiments having multiple similar capacitive sensors and capacitive sensing circuits, only one transistor need be added to each capacitive sensing circuit to compensate for leakage current.
Abstract:
In an embodiment, a transmitter includes a transmission path that is configurable to generate first pilot clusters each including a respective first pilot subsymbol in a first cluster position and a respective second pilot subsymbol in a second cluster position such that a vector formed by the first pilot subsymbols is orthogonal to a vector formed by the second pilot subsymbols. For example, where such a transmitter transmits simultaneous orthogonal-frequency-division-multiplexed (OFDM) signals (e.g., MIMO-OFDM signals) over respective channels that may impart inter-carrier interference (ICI) to the signals due to Doppler spread, the pattern of the pilot symbols that compose the pilot clusters may allow a receiver of these signals to estimate the responses of these channels more accurately than conventional receivers.
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:
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.