Capacitance sensing circuit and fingerprint identification system
AssigneeShenzhen Goodix Technology Co., Ltd.
InventorsYu-An Liang, Meng-Ta Yang
Life of this patent
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Abstract
The present application provides a capacitance sensing circuit, comprising an integrating circuit, comprising an integrating input terminal, coupled to the touch capacitance, wherein the integrating input terminal receives an input voltage; and an integrating output terminal, configured to output an output voltage; a comparator; a positive digital-to-analog (DA) converting unit; a negative DA converting unit; a control circuit, configured to control the positive DA converting unit and the negative DA converting unit; and a logic circuit, configured to output an output code, wherein the output code is related to a capacitance of the touch capacitance.
Claims18
A capacitance sensing circuit, configured to sense a touch capacitance, the capacitance sensing circuit comprising:
- an integrating circuit, comprising:
- an integrating input terminal, coupled to the touch capacitance, wherein the integrating input terminal receives an input voltage;
- and
- an integrating output terminal, configured to output an output voltage;
- a comparator, comprising:
- a first input terminal, coupled to the integrating output terminal;
- and
- a second input terminal, configured to receive a reference voltage;
- a positive digital-to-analog (DA) converting unit, coupled to the integrating input terminal;
- a negative DA converting unit, coupled to the integrating input terminal;
- a control circuit, coupled to a comparing output terminal of the comparator, configured to control the positive DA converting unit and the negative DA converting unit;
- and
- a logic circuit, coupled to the comparing output terminal, configured to generate a first code within an integrating interval and generate a second code within a comparing interval, wherein the logic circuit outputs an output code according to the first code and the second code, and the output code is related to a capacitance of the touch capacitance.
A fingerprint identification system, comprising:
- a plurality of pixel circuits, configured to form a plurality of touch capacitances with a finger;
- and
- a capacitance sensing circuit, coupled to the plurality of pixel circuits, configured to sense the plurality of touch capacitances, the capacitance sensing circuit comprising:
- an integrating circuit, comprising:
- an integrating input terminal, wherein the integrating input terminal is configured to receive an input voltage;
- and
- an integrating output terminal, configured to output an output voltage;
- a comparator, comprising:
- a first input terminal, coupled to the integrating output terminal;
- and
- a second input terminal, configured to receive a reference voltage;
- a positive DA converting unit, coupled to the integrating input terminal;
- a negative DA converting unit, coupled to the integrating input terminal;
- a control circuit, coupled to a comparing output terminal of the comparator, configured to control the positive DA converting unit and the negative DA converting unit;
- and
- a logic circuit, coupled to the comparing output terminal, configured to generate a first code within an integrating interval and generate a second code within a comparing interval, wherein the logic circuit outputs an output code according to the first code and the second code, and the output code is related to a touch capacitance of the plurality of touch capacitances.
Dependencies are inferred from the claim text.