Reducing sleep current in a capacitance sensing system

• US 10,788,937 B2
• Filed: 09/13/2018
• Issued: 09/29/2020
• Est. Priority Date: 05/07/2007
• Status: Active Grant

• Current Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Original Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Inventors: Wright, David G.
• Primary Examiner(s): Jansen, II, Michael J
• Application Number:
  US16/130,235
• Publication Number:
  US 20190012010A1
• Time in Patent Office: 747 Days
• CPC Class Codes: G06F 1/3203 Power management, i.e. event-based initiation of a power-saving mode
• CPC Class Codes: G06F 1/3262 Power saving in digitizer or tablet
• CPC Class Codes: G06F 2203/04106 Multi-sensing digitiser, i.e. digitiser using at least two different sensing technologies simultaneously or alternatively, e.g. for detecting pen and finger, for saving power or for improving position detection
• 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 3/03548 Sliders, in which the moving part moves in a plane
• CPC Class Codes: G06F 3/042 by opto-electronic means
• CPC Class Codes: G06F 3/044 by capacitive means
• CPC Class Codes: G09G 2330/022 in absence of operation, e.g. no data being entered during a predetermined time
• CPC Class Codes: G09G 3/20 for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
• CPC Class Codes: H03K 17/9622 using a plurality of detectors, e.g. keyboard

Abstract

An apparatus and method of measuring a collective capacitance on a group of capacitive sense elements from at least one of rows or columns of a capacitance sense array when in a first mode, and individually measuring capacitances on each of the rows and columns when in a second mode.

Claims

1. A method, comprising:

individually measuring a capacitance on at least two of a plurality of sensor elements of a device;

determining if a conductive object is in proximity to each of the at least two of the plurality of sensor elements;

coupling a group of sensor elements of the plurality of sensor elements together with at least one selection circuit when a proximity of a conductive object to the device is not detected on the plurality of sensor elements while individually measuring the capacitance on the at least two of the plurality of sensor elements, the selection circuit disposed between the plurality of sensor elements and a measurement circuit;

performing a baseline measurement of the group of sensor elements;

collectively measuring a capacitance on the group of sensor elements;

determining whether a conductive object is proximate to the device using the group of sensor elements; and

placing the device in a reduced power mode when the conductive object is not proximate to the device.

2. The method of claim 1, further comprising:

individually measuring a capacitance on each of the plurality of sensor elements when the conductive object is proximate to the device, wherein placing the device in the reduced power mode further comprises placing the device in the reduced power mode for a period of time when the conductive object is not proximate to the device; and

collectively measuring a capacitance on the group of sensor elements after the period of time.

3. The method of claim 1, wherein determining whether the conductive object is proximate to the device comprises detecting a proximity of a conductive object to the device while the group of sensor elements are coupled together by the at least one selection circuit.

4. The method of claim 3, further comprising performing a baseline measurement on the group of sensor elements after coupling the group of sensor elements together, wherein the baseline measurement is representative of the capacitance on the group of sensor elements when a conductive object is not proximate to the device.

5. The method of claim 4, wherein determining whether the conductive object is proximate to the device further comprises determining whether the collectively measured capacitance on the group of sensor elements is greater than the baseline measurement.

6. The method of claim 1, wherein coupling the group of sensor elements comprises coupling all of the plurality of sensor elements together.

7. The method of claim 1, wherein coupling the group of sensor elements comprises coupling a fraction of the plurality of sensor elements together.

8. The method of claim 1, wherein coupling the group of sensor elements comprising coupling a first fraction of the plurality of sensor elements together with the first selection circuit and coupling a second fraction of the plurality of sensor elements together with a second selection circuit.

9. The method of claim 8, wherein the first fraction and the second fraction are mutually exclusive.

10. The method of claim 8, wherein a capacitance of the first fraction of the plurality of sensor elements is measured at a first time and a capacitance of the second fraction of the plurality of sensor elements is measured at a second time.

11. The method of claim 1, wherein the coupling of the group of sensor elements of the plurality of sensor elements together comprises closing a plurality of switches associated with each of the sensor elements coupled together.