Self capacitance touch sensing
First Claim
Patent Images
1. A touch sensitive device comprising:
- a cancelation circuit comprising a numerically controlled oscillator coupled to an input of a push/pull current source, the push/pull current source capable of generating a cancelation signal based on parasitic capacitance affecting a self capacitance signal, wherein;
the cancelation circuit is configured to generate a time-varying signal and scale the time-varying signal to generate an amplitude-controlled time-varying signal based on the parasitic capacitance to adjust a magnitude of the cancelation signal, the amplitude-controlled time-varying signal controlling the magnitude of the cancelation signal generated by the push/pull current source, andthe cancelation signal is coupled to the self capacitance signal so as to cancel the parasitic capacitance from the self capacitance signal; and
a sense circuit capable of receiving the self capacitance signal with the parasitic capacitance canceled therefrom and a stimulation signal, and outputting a touch signal in response to the self capacitance signal with the parasitic capacitance canceled therefrom and the stimulation signal.
1 Assignment
0 Petitions
Accused Products
Abstract
Self capacitance touch circuits to cancel the effects of parasitic capacitance in a touch sensitive device are disclosed. One circuit can generate a parasitic capacitance cancelation signal that can be injected into touch sensing circuitry to cancel the parasitic capacitance. Another circuit can adjust the phase and magnitude of the parasitic capacitance cancelation signal based on characteristics of channels in the touch sensing circuitry so as to fine tune the parasitic capacitance cancelations. Another circuit can drive a guard plate and touch panel electrodes so as to cancel the parasitic capacitances between the panel and the plate and between the electrodes.
-
Citations
23 Claims
-
1. A touch sensitive device comprising:
-
a cancelation circuit comprising a numerically controlled oscillator coupled to an input of a push/pull current source, the push/pull current source capable of generating a cancelation signal based on parasitic capacitance affecting a self capacitance signal, wherein; the cancelation circuit is configured to generate a time-varying signal and scale the time-varying signal to generate an amplitude-controlled time-varying signal based on the parasitic capacitance to adjust a magnitude of the cancelation signal, the amplitude-controlled time-varying signal controlling the magnitude of the cancelation signal generated by the push/pull current source, and the cancelation signal is coupled to the self capacitance signal so as to cancel the parasitic capacitance from the self capacitance signal; and a sense circuit capable of receiving the self capacitance signal with the parasitic capacitance canceled therefrom and a stimulation signal, and outputting a touch signal in response to the self capacitance signal with the parasitic capacitance canceled therefrom and the stimulation signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
-
-
20. A method for canceling effects of parasitic capacitance in a touch sensitive panel, the method comprising:
-
generating a self capacitance signal indicative of an object proximate to the panel, the self capacitance signal being affected by a parasitic capacitance; generating, with a push/pull current source, a cancelation signal at a cancelation circuit comprising a numerically controlled oscillator coupled to an input of the push/pull current source based on the parasitic capacitance, wherein the cancelation circuit is configured to generate a time-varying signal and scale the time-varying signal to generate an amplitude-controlled time-varying signal based on the parasitic capacitance to adjust the magnitude of the cancelation signal, the amplitude-controlled time-varying signal controlling the magnitude of the cancelation signal generated by the push/pull current source; coupling the cancelation signal with the self capacitance signal to cancel the parasitic capacitance therefrom; and generating a touch signal indicative of the proximate object at a sense circuit in response to a first input of the self capacitance signal with the parasitic capacitance canceled therefrom and a second input of a stimulation signal. - View Dependent Claims (21)
-
-
22. A touch sensing system comprising:
-
a cancelation circuit comprising a numerically controlled oscillator coupled to an input of a push/pull current source capable of generating a cancelation signal based on a parasitic capacitance, the cancelation circuit configured to generate a time-varying signal and scale the time-varying signal to generate an amplitude-controlled time-varying signal based on the parasitic capacitance to adjust a magnitude of the cancelation signal, the amplitude-controlled time-varying signal controlling the magnitude of the cancelation signal generated by the push/pull current source; the cancelation circuit capable of using the cancelation signal to cancel the parasitic capacitance from a self capacitance signal generated at a touch node; and a receive circuit capable of receiving the self capacitance signal and a stimulation signal, and outputting a touch signal in response to the self capacitance signal and the stimulation signal. - View Dependent Claims (23)
-
Specification