Capacitive field sensor with sigma-delta modulator

• US 10,025,441 B2
• Filed: 09/07/2016
• Issued: 07/17/2018
• Est. Priority Date: 07/03/2007
• Status: Active Grant

• Current Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Original Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Inventors: Ryshtun, Andriy, Kremin, Viktor
• Primary Examiner(s): Nguyen, Vincent Q
• Application Number:
  US15/258,151
• Publication Number:
  US 20160378227A1
• Time in Patent Office: 678 Days
• Field of Search: 324658-663, 324679-687
• CPC Class Codes: G01R 27/2605 Measuring capacitance capacitive sensors G01D5/24
• CPC Class Codes: G06F 2203/04101 2.5D-digitiser, i.e. digitiser detecting the X/Y position of the input means, finger or stylus, also when it does not touch, but is proximate to the digitiser's interaction surface and also measures the distance of the input means within a short range in the Z direction, possibly with a separate measurement setup
• CPC Class Codes: G06F 2203/04107 Shielding in digitiser, i.e. guard or shielding arrangements, mostly for capacitive touchscreens, e.g. driven shields, driven grounds
• CPC Class Codes: G06F 2203/04108 Touchless 2D- digitiser, i.e. digitiser detecting the X/Y position of the input means, finger or stylus, also when it does not touch, but is proximate to the digitiser's interaction surface without distance measurement in the Z direction
• CPC Class Codes: G06F 3/0416 Control or interface arrangements specially adapted for digitisers
• CPC Class Codes: G06F 3/04166 Details of scanning methods, e.g. sampling time, grouping of sub areas or time sharing with display driving Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally G06F3/04184
• CPC Class Codes: G06F 3/044 by capacitive means
• CPC Class Codes: H03K 17/962 Capacitive touch switches
• CPC Class Codes: H03K 2017/9613 using two electrodes per touch switch
• CPC Class Codes: H03K 2217/960725 Charge-transfer
• CPC Class Codes: H03K 2217/96074 Switched capacitor
• CPC Class Codes: H03K 2217/960745 Capacitive differential; e.g. comparison with reference capacitance

Abstract

A capacitive sensor includes a switching capacitor circuit, a comparator, and a charge dissipation circuit. The switching capacitor circuit reciprocally couples a sensing capacitor in series with a modulation capacitor during a first switching phase and discharges the sensing capacitor during a second switching phase. The comparator is coupled to compare a voltage potential on the modulation capacitor to a reference and to generate a modulation signal in response. The charge dissipation circuit is coupled to the modulation capacitor to selectively discharge the modulation capacitor in response to the modulation signal.

Claims

1. A system comprising:

a field sensor capacitor, wherein a first current is generated on the field sensor capacitor;

a processing device comprising;

a summing capacitor coupled to the field sensor capacitor, wherein the summing capacitor is charged at least in part by the first current;

a modulation circuit coupled with the field sensor capacitor and the summing capacitor, wherein the modulation circuit is configured to modulate a signal based on the charge of the summing capacitor, wherein the modulation circuit is separate from the summing capacitor; and

a measurement circuit coupled to the modulation circuit, wherein the measurement circuit is configured to output a measurement signal.

2. The system of claim 1, wherein the processing device further comprises at least one diode coupled between the field sensor capacitor and the summing capacitor.

3. The system of claim 1, wherein the measurement signal indicates a capacitance of the field sensor capacitor.

4. The system of claim 1, wherein the measurement signal indicates whether an object is proximate to the field sensor capacitor.

5. The system of claim 1, wherein the processing device comprises one or more integrated circuit (IC) devices.

6. The system of claim 1, wherein the system comprises a mobile handset.