Capacitance touch near-field—far field switching
A touch sensor panel configured to switch between a mutual capacitance near field sensing architecture and a self-capacitance far field sensing architecture. The touch sensor panel includes circuitry that can switch the configuration of touch electrodes to act as either drive lines in a mutual capacitance configuration or as sense electrodes in a self-capacitance configuration. The touch sensor panel also includes circuitry that can switch the configuration of touch electrodes to act as either sense lines in a mutual capacitance configuration or a sense electrode in a self-capacitance configuration.
1. A method for switching a touch sensor panel between a self-capacitance configuration and a mutual capacitance configuration, the method comprising:
configuring a first set of multiple lines as sense electrodes in a self-capacitance configuration by applying a stimulation signal to the first set of multiple lines through one or more virtual ground charge amplifiers, and as drive lines in a mutual capacitance configuration; and
configuring a second set of multiple lines as sense electrodes in either a self-capacitance configuration or a mutual capacitance configuration.
2. The method of claim 1 , wherein configuring the first set of multiple lines as drive lines comprises coupling one or more drivers to the first set of multiple lines.
3. The method of claim 2 , further comprising configuring the one or more drivers to generate either a stimulation signal or a reference voltage.
4. The method of claim 1 , wherein configuring the first set of multiple lines as sense electrodes comprises coupling the one or more virtual ground charge amplifiers to the first set of multiple lines.
5. The method of claim 4 , further comprising selectively configuring a feedback resistance and capacitance of the virtual ground charge amplifier for super far field sensing or far field sensing.
6. The method of claim 4 , further comprising reducing a parasitic capacitance of the touch sensor panel by:
applying a sinusoidal signal to a positive input of at least one of the one or more virtual ground charge amplifiers; and
driving one or more shields of the touch sensor panel with a signal having substantially the same frequency and phase as the sinusoidal signal.
7. A touch controller for operating a touch sensor panel in a self-capacitance configuration or a mutual capacitance configuration, comprising:
a plurality of input/output (I/O) lines for connecting to the touch sensor panel;
a plurality of drivers configured for providing first stimulation signals to the touch sensor panel;
one or more sense amplifiers configured for receiving sense signals from the touch sensor panel; and
switching circuitry coupled to the plurality of I/O lines, plurality of drivers, and one or more sense amplifiers, the switching circuitry configured for coupling the plurality of drivers to the plurality of I/O lines in the mutual capacitance configuration, and for coupling the one or more sense amplifiers to the plurality of I/O lines and applying a second stimulation signal to the plurality of I/O lines through the one or more sense amplifiers in the self-capacitance configuration.
8. The touch controller of claim 7 , further comprising a multiplexer configured for selectively coupling a first number of I/O lines to a second number of sense amplifiers, wherein the first number is greater than the second number.
9. The touch controller of claim 7 , wherein the plurality of drivers are configured to generate either the first stimulation signals or a reference voltage.
10. The touch controller of claim 7 , wherein the sense amplifier is configured as a virtual ground charge amplifier.
11. The touch controller of claim 10 , wherein the virtual ground charge amplifier is selectively configurable to provide a feedback resistance and capacitance for super far field sensing or far field sensing.
12. The touch controller of claim 10 , wherein the virtual ground charge amplifier is configured to receive a sinusoidal signal on its positive input.
13. The touch controller of claim 7 , the touch controller coupled to a touch sensor panel, the touch sensor panel comprising:
a plurality of first lines coupled to the plurality of I/O lines and configurable to be drive lines in the mutual capacitance configuration and sense lines in the self-capacitance configuration; and
a plurality of second lines configured to be sense lines in both the mutual and self-capacitance configurations.
14. The touch controller of claim 7 , wherein the touch controller and touch sensor panel are integrated into a computing device.
15. A computing device including a touch controller, the touch controller comprising:
a plurality of input/output (I/O) lines for connecting to the touch sensor panel;
a plurality of drivers configured for providing first stimulation signals to the touch sensor panel;
one or more sense amplifiers configured for receiving sense signals from the touch sensor panel; and
switching circuitry coupled to the plurality of I/O lines, plurality of drivers, and one or more sense amplifiers, the switching circuitry configured for coupling the plurality of drivers to the plurality of I/O lines in the mutual capacitance configuration, and for coupling the one or more sense amplifiers to the plurality of I/O lines and applying a second stimulation signal to the plurality of I/O lines through the one or more sense amplifiers in the self-capacitance configuration.