Capacitance detector circuit, capacitance detection method, and fingerprint sensor using the same
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United States of America Patent
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Jul 11, 2006
Grant Date -
Apr 7, 2005
app pub date -
Sep 14, 2004
filing date -
Oct 2, 2003
priority date (Note) -
In Force
status (Latency Note)
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Abstract
A capacitance detecting circuit of a capacitive sensor having a plurality of column lines and a row line intersecting the column lines detects a change in capacitance at an intersection of a column line and a row line. The circuit includes a PN code generating unit for generating a code having orthogonality in time sequence to output the generated code as a column drive signal, a column line drive unit for driving a predetermined one of the column lines which are selected in response to the code, a capacitance detecting unit, connected to the row line, for detecting a voltage by converting a total sum of changes in capacitance at intersections of the selected column lines into the voltage to output the detected voltage, and a decode processing unit for performing a predetermined calculation on the detected voltage output from the capacitance detecting unit and the code to determine a voltage value responsive to the capacitance change at the intersection.
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