Positioning components that provide resistance on sense lines of a touch sensor
In certain embodiments, a system includes first and second resistive components and a touch sensor controller. The first component is positioned on a first sense line connected to an in-cell touch sensor. The first resistive component is set to a value modifying an RC time constant of a first electrode of the touch sensor. The second resistive component is positioned on a second sense line connected to the in-cell touch sensor. The second component is set to a value modifying an RC time constant of a second electrode of the touch sensor. The value of the modified RC time constant of the first electrode is within 100% of the value of the modified RC time constant of the second electrode. The controller receives signals from the first and second sense lines, such that the first and second resistive components are between the controller and the first and second electrodes, respectively.
1. A system, comprising:
a display system configured to send a display signal to one or more pixels of a display along a data line, the display comprising display layers;
an in-cell touch sensor comprising electrodes configured to provide signals for locating touches of the display, the in-cell touch sensor comprising one or more layers embedded within the display layers, wherein:
the data line is capacitively coupled to a first electrode and a second electrode of the electrodes;
a first circuit comprises the first electrode coupled to a first sense line; and
a second circuit comprises the second electrode coupled to a second sense line,
a touch sensor controller configured to receive signals from the first sense line of the first circuit and second sense line of the second circuit;
a first resistive component associated with the first sense line, wherein the first resistive component is set to a value and configured to alter a time response of the first circuit;
a second resistive component associated with the second sense line, wherein the second resistive component is set to a value and configured to alter a time response of the second circuit;
an inverter configured to receive a signal associated with the second circuit and generate an inverted signal responsive to the received signal; and
a summer, the summer configured to receive and sum a first signal associated with the first circuit and the inverted signal.
2. The system of claim 1 , wherein the data line, the first electrode, and second electrode are located such that a display signal sent along the data line results in a noise signal in each of the first and second electrodes.
3. The system of claim 1 , wherein:
the length of the first sense line is different from the length of the second sense line; and
a total resistance value of each of the first and second sense lines are different.
4. The system of claim 1 , wherein the resistive component associated with each of the first and second electrodes comprises a resistor.
5. The system of claim 1 , wherein the altered time response of the first and second circuits is an altered RC time constant, and a value of the altered RC time constant of the first circuit is within 100% of a value of the altered RC time constant of the second circuit.
6. The system of claim 1 , wherein the altered time response of the first and second circuits is an altered RC time constant, and a value of an altered RC time constant of the first circuit is within 50% of a value of the altered RC time constant of the second circuit.
7. The system of claim 1 , wherein the altered time response of the first and second circuits is an altered RC time constant, and a value of an altered RC time constant of the first circuit is within 5% of a value of the altered RC time constant of the second circuit.
8. The system of claim 1 , further comprising:
a first current amplifier operably coupled to the first sense line between the first resistive component and the touch sensor controller, wherein:
an input of the first current amplifier is connected to the first sense line toward the first resistive component; and
a non-inverted output of the first current amplifier is connected to the first sense line toward the in-cell touch sensor; and
a second current amplifier operably coupled to the second sense line between the second resistive component and the touch sensor controller, wherein:
an input of the second current amplifier is connected to the second sense line toward the second resistive component;
a non-inverted output of the second current amplifier is connected to the second sense line toward the in-cell touch sensor; and
an inverted output of the second current amplifier is connected to the first sense line at a location between the first current amplifier and the touch sensor controller.
9. The system of claim 8 , wherein the inverted output of the second current amplifier is connected to the first sense line at a summing node located between the first current amplifier and the touch sensor controller, wherein the summing node is configured to:
sum the non-inverted output of the first current amplifier and the inverted output of the second current amplifier; and
output the sum on the first sense line between the summing node and the touch sensor controller.
10. The system of claim 9 , wherein an inverter is operably coupled to the first sense line between the summing node and the touch sensor controller, and wherein the input of the inverter is the output of the summing node and the output of the inverter is connected to the first sense line toward the touch sensor controller.
11. The system of claim 10 , wherein a sampler is operably coupled to the first sense line between the inverter and the touch sensor controller, and wherein the input of the sampler is the output of the inverter and the output of the sampler is connected to the first sense line toward the touch sensor controller.
12. A system, comprising:
a first resistive component positioned on a first sense line connected to an in-cell touch sensor, wherein the first resistive component is set to a value configured to modify an RC time constant of a first electrode of the in-cell touch sensor connected to the first sense line;
a second resistive component positioned on a second sense line connected to the in-cell touch sensor, wherein the second resistive component is set to a value configured to modify an RC time constant of a second electrode of the in-cell touch sensor connected to the second sense line;
an inverter configured to receive a signal associated with the second electrode and generate an inverted signal responsive to the received signal;
a summer, the summer configured to receive and sum a first signal associated with the first electrode and the inverted signal; and
a touch sensor controller configured to receive signals from the first and second sense lines.
13. The system of claim 12 , wherein a value of a modified RC time constant of the first electrode is within 100% of a value of a modified RC time constant of the second electrode.
14. The system of claim 12 , wherein a value of a modified RC time constant of the first electrode is within 10% of a value of a modified RC time constant of the second electrode.
15. The system of claim 12 , further comprising:
a first current amplifier positioned on the first sense line between the first resistive component and the touch sensor controller, wherein:
an input of the first current amplifier is connected to the first sense line toward the first resistive component; and
a non-inverted output of the first current amplifier is connected to the first sense line toward the in-cell touch sensor; and
a second current amplifier positioned on the second sense line between the second resistive component and the touch sensor controller, wherein:
an input of the second current amplifier is connected to the second sense line toward the second resistive component;
a non-inverted output of the second current amplifier is connected to the second sense line toward the in-cell touch sensor; and
an inverted output of the second current amplifier is connected to the first sense line at a location between the first current amplifier and the touch sensor controller.
16. The system of claim 15 , wherein the inverted output of the second current amplifier is connected to the first sense line at a summing node located between the first current amplifier and the touch sensor controller, wherein the summing node is configured to:
sum the non-inverted output of the first current amplifier and the inverted output of the second current amplifier; and
output the sum on the first sense line between the summing node and the touch sensor controller.
17. The system of claim 16 , wherein an inverter is positioned on the first sense line between the summing node and the touch sensor controller, and wherein the input of the inverter is the output of the summing node and the output of the inverter is connected to the first sense line toward the touch sensor controller.
18. The system of claim 17 , wherein a sampler is positioned on the first sense line between the inverter and the touch sensor controller, and wherein the input of the sampler is the output of the inverter and the output of the sampler is connected to the first sense line toward the touch sensor controller.
19. A method, comprising:
determining a first time response for a first electrode of an in-cell touch sensor;
determining a second time response for a second electrode of the in-cell touch sensor, wherein the first time response is different than the second time response; and
setting one or more resistive components associated with at least one of the first and second electrodes, such that:
a difference between the first time response and the second time response after setting the one or more resistive components is smaller than the difference between the first time response and the second time response before setting the one or more resistive components;
the first time response being within 100% of the second time response; and
a first noise signal and a second noise signal, emanating from the first and second electrodes, respectively, responsive to a display signal sent along a data line capacitively coupled to both the first and second electrodes, arrive at a touch system closer together in time than they would before the setting of the one or more resistive components and are cancelled.
20. The method of claim 19 , further comprising canceling some of the first noise signal by summing it with an inverted representation of the second noise signal.
21. The method of claim 19 , further comprising canceling more than 95% of the first noise signal by summing it with an inverted representation of the second noise signal.
22. The method of claim 19 , wherein setting one or more components to provide resistance associated with at least one of the first and second electrodes comprises:
setting a value of a first resistive component associated with the first electrode; and
setting a value of a second resistive component associated with the second electrode.
23. The method of claim 19 , wherein the method is performed during a start-up mode of a display system.
24. The method of claim 19 , wherein the method is performed during integration of a display panel and the in-cell touch sensor.
25. A touch screen, comprising:
a first resistive component associated with a first electrode operably coupled to a first sense line connected to an in-cell touch sensor, wherein the first resistive component is operable to modify a value of an RC time constant of the first electrode;
a second resistive component associated with a second electrode operably coupled to a second sense line connected to the in-cell touch sensor, wherein the second resistive component is operable to modify a value of an RC time constant of the second electrode;
an inverter configured to receive a signal associated with the second electrode and generate an inverted signal responsive to the received signal;
a summer, the summer configured to receive and sum a first signal associated with the first electrode and the inverted signal; and
a touch sensor controller operably coupled to the first and second sense lines.