Base capacitance compensation for a touchpad sensor

• US 20070070049A1
• Filed: 09/20/2006
• Published: 03/29/2007
• Est. Priority Date: 09/23/2005
• Status: Active Grant

• Current Assignee: Elan Microelectronics Corporation
• Original Assignee: Elan Microelectronics Corporation
• Inventors: Lee, Wen-Kai, Yang, Tso-Chieh, Yang, Chen-Yao
• Granted Patent: US 8,115,750 B2
• Time in Patent Office: Days
• US Class Current: 345/173
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes

Abstract

For a compensation to the sensed capacitive values of a touchpad sensor, the variance profile of the base capacitance or the sensed capacitive values of the traces in the touchpad sensor is determined, and then a firmware operation based on the variance profile is carried out to modify the sensed capacitive values or the position value when an object touches on the touchpad sensor, such that the touchpad sensor operates as a symmetrical touchpad sensor does.

Claims

1. A compensation to sensed capacitive values of a touchpad sensor, comprising the steps of:

calculating base capacitances of a plurality of traces in the touchpad sensor for determining a distribution of the base capacitances across the touchpad sensor;

analyzing the distribution for determining a variance profile of the base capacitances; and

proceeding a firmware operation based on the variance profile to modify the sensed capacitive values such that they look like produced from a symmetrical touchpad sensor.

2. The compensation of claim 1, wherein the step of proceeding a firmware operation comprises the step of carrying out addition/subtraction or multiplication/division operations to the sensed capacitive values.

3. The compensation of claim 1, wherein the step of proceeding a firmware operation comprises the step of adjusting a charge/discharge frequency for the plurality of traces.

4. The compensation of claim 3, wherein the step of adjusting a charge/discharge frequency for the plurality of traces comprises the step of increasing the charge/discharge frequency for one or more of the plurality of traces which have greater base capacitances.

5. The compensation of claim 1, wherein the step of proceeding a firmware operation comprises the step of adjusting a charge/discharge current for the plurality of traces.

6. The compensation of claim 5, wherein the step of adjusting a charge/discharge current for the plurality of traces comprises the step of increasing the charge/discharge current for one or more of the plurality of traces which have greater base capacitances.

7. The compensation of claim 1, wherein the plurality of traces are selected from a sensing layer.

8. The compensation of claim 1, wherein the plurality of traces are selected from at least two sensing layers.

9. A compensation to sensed capacitive values of a touchpad sensor, comprising the steps of:

calculating a position value of an object on the touchpad sensor;

calculating a variance profile of the sensed capacitive values of a plurality of traces in the touchpad sensor; and

proceeding a firmware operation based on the variance profile to modify the position value for eliminating an offset in the position value.

10. The compensation of claim 9, wherein the step of proceeding a firmware operation comprises the step of increasing or decreasing the position value.

11. The compensation of claim 9, wherein the plurality of traces are selected from a sensing layer.