Touch controllers capable of reducing noise interference
A touch controller coupled to a touch sensor panel and arranged to detect touch events on the touch sensor panel includes a sensing circuit. The sensing circuit includes an integrator circuit and a reference voltage controlling circuit. The integrator circuit includes a first input node coupled to a sensing node for receiving a sensing signal, a second input node coupled to a guard trace disposed adjacent to the touch sensor panel and an output node outputting an integrated signal. The reference voltage controlling circuit includes a switch coupled between the second input node of the integrator circuit and a voltage source providing a reference voltage. The switch is closed during a pre-charge period to charge a voltage on the guard trace to the reference voltage in beginning of a sensing period and is opened after the pre-charge period.
1. A touch controller, coupled to a touch sensor panel and
arranged to detect touch events on the touch sensor panel, comprising:
a sensing circuit, comprising:
an integrator circuit, comprising:
a first input node, coupled to a sensing node for receiving a sensing signal;
a second input node, coupled to a guard trace disposed adjacent to the touch sensor panel; and
an output node, outputting an integrated signal; and
a reference voltage controlling circuit, comprising:
a switch, coupled between the second input node of the integrator circuit and a voltage source providing a reference voltage; and
a capacitor, coupled between the guard trace and the second input node of the integrator circuit
wherein the switch is closed during a pre-charge period of a sensing period to charge a voltage on the guard trace to the reference voltage and is opened after the pre-charge period, wherein the pre-charge period occurs at the beginning of the sensing period and does not comprise the entire sensing period.
2. The touch controller of claim 1 , further comprising:
an analog to digital converter, coupled to the output node of the integrator circuit and arranged to receive the integrated signal and convert the integrated signal to generate a converted signal; and
a signal processing circuit, coupled to the analog to digital converter and arranged to receive the converted signal and process the converted signal to determine whether there is any touch event on the touch sensor panel.
3. The touch controller of claim 1 , wherein the reference voltage controlling circuit further comprises:
a resistor, coupled between the second input node of the integrator circuit and the voltage source.
4. The touch controller of claim 1 , wherein the guard trace is a floating trace when the switch is opened.
5. The touch controller of claim 2 , wherein the signal processing circuit is further arranged to generate a pre-charge control signal for controlling the switch to close during the pre-charge period of the sensing period.
6. A touch sensing device, comprising:
a guard trace, disposed adjacent to a touch sensor panel; and
a touch controller, coupled to the touch sensor panel and arranged to detect touch events on the touch sensor panel, comprising:
a sensing circuit, comprising:
an integrator circuit, comprising:
a first input node, coupled to a sensing node for receiving a sensing signal;
a second input node, coupled to the guard trace; and
an output node, outputting an integrated signal; and
a reference voltage controlling circuit, comprising:
a switch, coupled between the second input node of the integrator circuit and a voltage source providing a reference voltage; and
a capacitor, coupled between the guard trace and the second input node of the integrator circuit;
wherein the switch is closed during a pre-charge period of a sensing period to charge a voltage on the guard trace to the reference voltage and is opened after the pre-charge period, wherein the pre-charge period occurs at the beginning of the sensing period and does not comprise the entire sensing period.
7. The touch sensing device of claim 6 , wherein the touch controller further comprises:
an analog to digital converter, coupled to the output node of the integrator circuit and arranged to receive the integrated signal and convert the integrated signal to generate a converted signal; and
a signal processing circuit, coupled to the analog to digital converter and arranged to receive the converted signal and process the converted signal to determine whether there is any touch event on the touch sensor panel.
8. The touch sensing device of claim 6 , wherein the reference voltage controlling circuit further comprises:
a resistor, coupled between the second input node of the integrator circuit and the voltage source.
9. The touch sensing device of claim 6 , wherein the guard trace is a floating trace when the switch is opened.
10. The touch sensing device of claim 7 , wherein the signal processing circuit is further arranged to generate a pre-charge control signal for controlling the switch to close during the pre-charge period of the sensing period.
11. A touch sensing module, comprising:
a touch sensor panel;
a guard trace, disposed adjacent to the touch sensor panel; and
a touch controller, coupled to the touch sensor panel and arranged to detect touch events on the touch sensor panel, comprising:
a sensing circuit, comprising:
an integrator circuit, comprising:
a first input node, coupled to a sensing node for receiving a sensing signal;
a second input node, coupled to the guard trace; and
an output node, outputting an integrated signal; and
a reference voltage controlling circuit, comprising:
a switch, coupled between the second input node of the integrator circuit and a voltage source providing a reference voltage; and
a capacitor, coupled between the guard trace and the second input node of the integrator circuit;
wherein the switch is closed during a pre-charge period of a sensing period to charge a voltage on the guard trace to the reference voltage and is opened after the pre-charge period, wherein the pre-charge period occurs at the beginning of the sensing period and does not comprise the entire sensing period.
12. The touch sensing module of claim 11 , wherein the touch controller further comprises:
an analog to digital converter, coupled to the output node of the integrator circuit and arranged to receive the integrated signal and convert the integrated signal to generate a converted signal; and
a signal processing circuit, coupled to the analog to digital converter and arranged to receive the converted signal and process the converted signal to determine whether there is any touch event on the touch sensor panel.
13. The touch sensing module of claim 11 , wherein the reference voltage controlling circuit further comprises:
a resistor, coupled between the second input node of the integrator circuit and the voltage source.
14. The touch sensing module of claim 11 , wherein the guard trace is a floating trace when the switch is opened.
15. The touch sensing module of claim 12 , wherein the signal processing circuit is further arranged to generate a pre-charge control signal for controlling the switch to close during the pre-charge period of the sensing period.