Active canceling of display noise in simultaneous display and touch sensing using an impulse response
First Claim
1. A processing system configured for simultaneously updating a display and performing capacitive sensing, the processing system comprising:
- a source driver configured to;
drive a source line with a reference voltage during a first time period in which a sensor electrode is not driven for capacitive sensing to produce first resulting signals on a routing trace coupled to the sensor electrode; and
drive the source line with a source driver signal during a second time period to produce second resulting signals on the routing trace during a third time period that at least partially overlaps with the second time period, the routing trace and the source line being routed proximate each other;
an analog-to-digital converter configured to;
receive the first resulting signals and generate a first digital signal representing the first resulting signals; and
receive the second resulting signals and generate a second digital signal representing the second resulting signals; and
an interference remover configured to remove source driver effects in the second resulting signals that exist due to driving the source line with the source driver signal by;
determining at least one impulse response, associated with receiver circuitry configured to process the first resulting signals, based on the first digital signal;
receiving the second digital signal;
calculating an interference value based on the source driver signal and the determined at least one impulse response; and
subtracting the calculated interference value from the second digital signal.
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Accused Products
Abstract
Techniques for removing display-based corrupting components from a capacitive sensing signal when display and capacitive sensing is performed at or nearly at the same time. A routing carrying display related signals (e.g., a source signal for sub-pixel updating) may induce a corrupting current into a routing for carrying capacitive sensing signals. This corrupting current would reduce the ability to determine presence of an input object via the sensing signal. Therefore, the corrupting signal is effectively removed from a signal received from a sensor electrode when driven for sensing. The corrupting component may be removed either in analog or digitally. In analog, the corrupting component is removed via a tunable capacitance. Digitally, a corrupting component is calculated as an impulse response convolved with the source driver voltage. This corrupting component is then subtracted from a digital value output by the sensing circuitry to obtain a “clean” value.
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Citations
16 Claims
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1. A processing system configured for simultaneously updating a display and performing capacitive sensing, the processing system comprising:
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a source driver configured to; drive a source line with a reference voltage during a first time period in which a sensor electrode is not driven for capacitive sensing to produce first resulting signals on a routing trace coupled to the sensor electrode; and drive the source line with a source driver signal during a second time period to produce second resulting signals on the routing trace during a third time period that at least partially overlaps with the second time period, the routing trace and the source line being routed proximate each other; an analog-to-digital converter configured to; receive the first resulting signals and generate a first digital signal representing the first resulting signals; and receive the second resulting signals and generate a second digital signal representing the second resulting signals; and an interference remover configured to remove source driver effects in the second resulting signals that exist due to driving the source line with the source driver signal by; determining at least one impulse response, associated with receiver circuitry configured to process the first resulting signals, based on the first digital signal; receiving the second digital signal; calculating an interference value based on the source driver signal and the determined at least one impulse response; and subtracting the calculated interference value from the second digital signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 16)
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8. An input device configured for simultaneously updating a display and performing capacitive sensing, the input device comprising:
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a sensor electrode coupled to a routing trace; a display element coupled to a source line, the source line and the routing trace being routed proximate each other; and a processing system coupled to the routing trace and the source line, the processing system comprising; a source driver configured to; drive the source line with a reference voltage during a first time period in which the sensor electrode is not driven for capacitive sensing to produce first resulting signals on the routing trace; and drive the source line with a source driver signal during a second time period to produce second resulting signals on the routing trace during a third time period that at least partially overlaps with the second time period, an analog-to-digital converter configured to; receive the first resulting signals and generate a first digital signal representing the resulting signals; and receive the second resulting signals and generate a second digital signal representing the second resulting signals; and an interference remover configured to remove source driver effects in the second resulting signals that exist due to driving the source line with the source driver signal by; determining at least one impulse response, associated with receiver circuitry configured to process the first resulting signals, based on the first digital signal; receiving the second digital signal; calculating an interference value based on the source driver signal and the determined at least one impulse response; and subtracting the calculated interference value from the second digital signal. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. A method for simultaneously updating a display and performing capacitive sensing, the method comprising:
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driving a source line with a reference voltage during a first time period in which a sensor electrode is not driven for capacitive sensing to produce first resulting signals on a routing trace coupled to the sensor electrode, the routing trace and the source line being routed proximate each other; driving the source line with a source driver signal during a second time period to produce second resulting signals on the routing trace during a third time period that at least partially overlaps with the second time period; receiving the first resulting signals; generating a first digital signal representing the first resulting signals; determining at least one impulse response, associated with receiver circuitry configured to process the first resulting signals, based on the first digital signal; receiving the second resulting signals; generating a second digital signal representing the second resulting signals; and removing source driver effects in the second resulting signals that exist due to driving the source line with the source driver signal by; receiving the second digital signal; calculating an interference value based on the source driver signal and the determined at least one impulse response; and subtracting the calculated interference value from the second digital signal.
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Specification