Touch controller with improved analog front end
AssigneeApple Inc.
InventorsSteven Porter Hotelling, Christoph Horst Krah
Life of this patent
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Abstract
A controller for a touch sensor includes a transimpedance amplifier, and a feedback resistor coupled to an input of the transimpedance amplifier and to an output of the transimpedance amplifier. At least one multiplexor may be coupled to the input of the transimpedance amplifier and configured to multiplex a plurality of analog inputs to one dedicated channel. The controller may further include a bandpass filter coupled to the output of the transimpedance amplifier. The output of the bandpass filter may be input to an anti-aliasing filter, which feeds into an analog to digital converter. Alternatively, the output of the bandpass filter may be input to a sigma-delta analog to digital converter.
Claims28
An analog front end for receiving a sense signal from a touch sensor, comprising:
- a transimpedance amplifier;
- a feedback resistor coupled to an input of the transimpedance amplifier and to an output of the transimpedance amplifier;
- and
- a bandpass filter coupled to the output of the transimpedance amplifier;
- wherein a gain of the bandpass filter is adjustable to increase noise headroom.
A method for receiving a sense signal from a touch sensor, comprising:
- amplifying an incoming signal using a transimpedance amplifier having a feedback resistor coupled to an input of the transimpedance amplifier and to an output of the transimpedance amplifier;
- and
- filtering an output of the transimpedance amplifier using a bandpass filter having a programmable center frequency;
- and
- adjusting a gain of the bandpass filter to increase noise headroom.
A controller for a touch sensor, comprising:
- a pre-amplifier;
- a feedback resistor coupled to an input of the pre-amplifier, an output of the pre-amplifier and a virtual ground;
- at least one capacitor coupled to the input of the pre-amplifier and the virtual ground;
- a sigma-delta analog to digital converter coupled to the output of the pre-amplifier;
- and
- a feedback circuit coupled between an output of the sigma-delta analog to digital converter and the input of the pre-amplifier to provide variable gain adjustment and bandpass filter response.
A controller for a touch sensor, comprising:
- a pre-amplifier, the input of which is coupled to a virtual ground;
- and
- a sigma-delta analog to digital converter coupled to the output of the pre-amplifier, wherein the sigma-delta analog to digital converter has bandpass filter response, with one or a plurality of feedback paths to the input of the pre-amplifier, which is held at virtual ground.
An analog front end for receiving a sense signal from a touch sensor, comprising:
- a biquad bandpass filter including a virtual ground input for rejecting stray capacitance from the touch sensor;
- and
- an analog to digital converter (ADC) coupled to the biquad bandpass filter.
Dependencies are inferred from the claim text.