Capacitive touch screen display system including circuitry to address display perturbations induced by panel sensing
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.
1. A touch panel control and sense circuit, comprising:
an input configured to receive a signal including information indicative of a display on condition of a video display panel;
a plurality of sense drive circuits configured to generate sense drive signals for application to sense lines of a touch panel; and
a controller configured to process the received signal and identify timing of the display on condition and further generate control signals that control actuation of the sense drive circuits, wherein said control signals applies a phase jitter to a leading edge of the sense drive signals such that said leading edges fall within a sense drive signal window that is synchronized to the display on condition.
2. The circuit of claim 1 , wherein the received signal comprises one or more of a horizontal synchronization signal or a vertical synchronization signal.
3. The circuit of claim 1 , wherein the received signal comprises a display on signal generated by said video display panel.
4. A system, comprising:
a video display system, including:
a video display panel; and
a video display drive circuit configured to control a display on condition of the video display panel;
a capacitive touch screen system, including:
a capacitive touch screen panel which is mounted on top of the video display panel; and
a touch panel control and sense circuit configured to operate the capacitive touch screen panel in a self-capacitance mode;
wherein the touch panel control and sense circuit comprises:
an input configured to receive a signal including information indicative of said display on condition of the video display panel;
a plurality of sense drive circuits configured to generate self-capacitance sense drive signals for application to sense lines of the capacitive touch screen panel; and
a controller configured to process the received signal and identify timing of the display on condition and further generate control signals that control actuation of the sense drive circuits, wherein said control signals apply a phase jitter to edges of the self-capacitance sense drive signals such that said edges fall within a sense drive signal window that is synchronized to the display on condition.
5. The system of claim 4 , wherein the received signal comprises one or more of a horizontal synchronization signal or a vertical synchronization signal derived from a video signal received by the video display drive circuit.
6. The system of claim 4 , wherein the video display drive circuit generates the signal including information indicative of said display on condition of the video display panel.
7. The system of claim 4 , wherein the capacitive touch screen panel comprises a plurality of capacitive signal lines coupled to outputs of the sense drive circuits.
8. The system of claim 7 , wherein the plurality of capacitive signal lines include intersecting horizontal and vertical lines.
9. The system of claim 7 , further including capacitive pads coupled at the ends of said plurality of capacitive signal lines, said capacitive pads arranged in an array.
10. A method, comprising:
detecting timing of a display on condition of a video display panel;
generating sense drive signals for application to sense lines of a capacitive touch panel; and
controlling sense drive signal generation to apply a phase jitter to edges of the sense drive signals such that said edges fall within a sense drive signal window that is synchronized to the display on condition.
11. The method of claim 10 , wherein the received signal comprises one or more of a horizontal synchronization signal and a vertical synchronization signal.
12. The method of claim 10 , wherein the received signal comprises a display on signal generated by said video display panel.