07521942 is referenced by 52 patents and cites 28 patents.

Methods, systems and devices are described for determining a measurable capacitance for proximity detection in a sensor having a plurality of sensing electrodes and at least one guarding electrode. A charge transfer process is executed for at least two executions. The charge transfer process includes applying a pre-determined voltage to at least one of the plurality of sensing electrodes using a first switch, applying a first guard voltage to the at least one guarding electrode using a second switch, sharing charge between the at least one of the plurality of sensing electrodes and a filter capacitance, and applying a second guard voltage different from the first guard voltage to the at least one guarding electrode. A voltage is measured on the filter capacitance for a number of measurements equal to at least one to produce at least one result to determine the measurable capacitance for proximity detection.

Title
Methods and systems for guarding a charge transfer capacitance sensor for proximity detection
Application Number
11/926411
Publication Number
7521942 (B2)
Application Date
October 29, 2007
Publication Date
April 21, 2009
Inventor
Joseph Kurth Reynolds
Sunnyvale
CA, US
Agent
Ingrassia Fisher & Lorenz P C
Assignee
Synaptics
CA, US
IPC
G01R 27/26
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