Invention Grant
- Patent Title: Capacitance measurement
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Application No.: US14802720Application Date: 2015-07-17
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Publication No.: US09958488B2Publication Date: 2018-05-01
- Inventor: Farzaneh Shahrokhi , Tracy Scott Dattalo , Joseph Kurth Reynolds , Adam Schwartz
- Applicant: Synaptics Incorporated
- Applicant Address: US CA San Jose
- Assignee: Synaptics Incorporated
- Current Assignee: Synaptics Incorporated
- Current Assignee Address: US CA San Jose
- Agency: FBFK PC
- Main IPC: G01R27/26
- IPC: G01R27/26 ; G01D5/24 ; G06F3/044 ; G06F3/041

Abstract:
A capacitance measurement circuit comprises a differential amplifier with first and second inputs and an output, first and second feedback capacitances, and a reset mechanism. The first input is coupled to a modulated reference voltage and the second input is coupled with a sensor electrode. A first feedback capacitance is coupled between the output and the second input. A second feedback capacitance is coupled between the output and the second input. The reset mechanism resets the first feedback capacitance to a first level of charge and the second feedback capacitance to a second level of charge. During an absolute capacitance measurement phase, the differential amplifier charges the sensor electrode while balancing voltages on the first and second inputs to a voltage level associated with the modulated reference voltage and integrates charge on the sensor electrode to measure capacitance corresponding to a coupling between the sensor electrode and an input object.
Public/Granted literature
- US20150323578A1 CAPACITANCE MEASUREMENT Public/Granted day:2015-11-12
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