Dual-mode capacitance sensing in a touch panel sensor

• US 9,582,123 B2
• Filed: 11/26/2012
• Issued: 02/28/2017
• Est. Priority Date: 11/26/2012
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Tiruvuru, Rajesh
• Primary Examiner(s): Boddie, William
• Assistant Examiner(s): EARLES, BRYAN E
• Application Number:
  US13/684,702
• Publication Number:
  US 20140145997A1
• Time in Patent Office: 1,555 Days
• US Class Current: 1/1
• 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 3/04164 Connections between sensors and controllers, e.g. routing lines between electrodes and connection pads
• CPC Class Codes: G06F 3/041661 using detection at multiple resolutions, e.g. coarse and fine scanning; using detection within a limited area, e.g. object tracking window
• CPC Class Codes: G06F 3/041662 using alternate mutual and self-capacitive scanning
• CPC Class Codes: G06F 3/04182 Filtering of noise external to the device and not generated by digitiser components
• CPC Class Codes: G06F 3/044 by capacitive means
• 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

A touch panel sensor system configured to measure mutual-capacitance and self-capacitance is disclosed. The touch panel sensor system includes a sensor configured to detect a change in capacitance associated with a touch event upon a touch panel and a measuring component. The measuring component is configured to detect mutual-capacitance during the first mode of operation and to detect self-capacitance during the second mode of operation. The system also includes a selection component that is configured to receive a selection signal to cause selection of the mode of operation. The system also includes a driver component coupled to the selection component and configured to generate a drive signal, which is furnished to the sensor during the first mode of operation and furnished to the measuring module during the second mode of operation. The amplitude characteristic of the drive signal may have differing values for the first and second modes of operation.

Claims

1. A system comprising:

a sensor comprising a plurality of row electrodes and a plurality of column electrodes crossing the row electrodes, the sensor configured to detect a change in capacitance associated with a touch event upon a touch panel;

a measuring component comprising a plurality of integrators each having a first input, a second input and an output, the first input being coupled to a corresponding one of the row electrodes, the measuring component configured to detect mutual-capacitance associated with the sensor during a first mode of operation and to detect self-capacitance associated with the sensor during a second mode of operation;

a selection component comprising a first input, a second input coupled to a ground, a first output coupled to at least one of the column electrodes, and a second output coupled to the second input of at least one of the integrators, the selection component configured to receive a selection signal to cause selection of at least the first mode of operation or the second mode of operation; and

a driver component coupled to the first input of the selection component, the driver component configured to generate a time-varying drive signal, the time-varying drive signal furnished to the sensor by way of the selection component, the time-varying drive signal having a first amplitude characteristic during the first mode of operation and a second amplitude characteristic different from the first amplitude characteristic during the second mode of operation, a magnitude of the difference between the first amplitude characteristic and the second amplitude characteristic being proportional to a difference between a change in mutual-capacitance associated with a touch event while in the first mode of operation and a change in self-capacitance associated with a touch event while in the second mode of operation.

2. The system as recited in claim 1, wherein each integrator of the plurality of integrators includes a charge amplifier having an integrating capacitor disposed between an inverting terminal and an output of the charge amplifier, wherein the charge amplifier outputs a signal having an amplitude characteristic that is proportional to a change in mutual-capacitance associated with the touch event during the first mode of operation and outputs a signal having an amplitude characteristic that is proportional to a change in self-capacitance associated with the touch event during the second mode of operation.

3. The system as recited in claim 1, wherein the driver component comprises a digital-to-analog converter coupled to a buffer, the buffer coupled to the sensor.

4. The system as recited in claim 1, further comprising a demodulator component coupled to the measuring component, the demodulator component configured to demodulate an analog signal furnished by the measuring component, the analog signal representing a change in mutual-capacitance corresponding to the touch event during the first mode of operation and representing a change in self-capacitance corresponding to the touch event during the second mode of operation.

5. The system as recited in claim 4, wherein the demodulator component comprises an analog-to-digital converter.

6. The system as recited in claim 1, wherein the sensor comprises a plurality of driving lines and a plurality of sensing lines across the plurality of driving lines, the plurality of driving lines and the plurality of sensing lines defining a coordinate system where each coordinate location comprises a capacitor.

7. The system as recited in claim 1, further comprising a control component coupled to the selection component, the control component configured to cause issuance of the selection signal to the selection component to cause selection of at least one of the first mode of operation or the second mode of operation.

8. The system as recited in claim 1, wherein the second amplitude characteristic is at least approximately ten times smaller than the first amplitude characteristic.

9. The system as recited in claim 7, wherein the control component generates the selection signal based on an event.

10. The system as recited in claim 7, wherein the control component generates the selection signal based on an application.

11. The system as recited in claim 7, wherein the control component generates the selection signal based on a change in frame rate or scan rate.

12. A touch panel system comprising:

sensor circuitry including a plurality of row electrodes and a plurality of column electrodes crossing the row electrodes;

driver circuitry configured to generate a time-varying drive signal;

control circuitry configured to generate a selection signal;

a measurement system including a plurality of row integrators each having a first input, a second input and an output, the first input being electrically coupled with a corresponding one of the row electrodes to detect a change in capacitance; and

selection circuitry including;

a first input electrically coupled with the driver circuitry to receive the drive signal, a second input electrically coupled with a ground, a first output electrically coupled with at least one of the column electrodes, and a second output electrically coupled with the second input of at least one of the row integrators, the selection circuitry configurable responsive to the selection signal;

for a first mode of operation, to provide the drive signal to the at least one column electrode, and ground the second input of the at least one row integrator; and

for a second mode of operation, to ground the at least one column electrode, and provide the drive signal to the second input of the at least one row integrator.

13. The touch panel system of claim 12, the first mode of operation being a mutual-capacitance sensing mode of operation, and the second mode of operation being a self-capacitance sensing mode of operation.

14. The touch panel system of claim 12, the driver circuitry being further configured to scale the drive signal based on the selection signal.

15. The touch panel system of claim 14, the driver circuitry being configured to scale the drive signal such that the drive signal has a first amplitude while in the first mode of operation and a second amplitude different than the first amplitude while in the second mode of operation, a scaling factor between the first amplitude and the second amplitude being proportional to a difference between a change in capacitance associated with a touch event while in the first mode of operation and a change in capacitance associated with a touch event while in the second mode of operation.

16. The touch panel system of claim 12, the selection circuitry including a first selection circuit including:

a first multiplexer configured to;

output the drive signal to the first output of the selection circuitry while in the first mode of operation,

ground the first output of the selection circuitry while in the second mode of operation; and

a second multiplexer configured to;

ground the second output of the selection circuitry while in the first mode of operation, and

output the drive signal to the second output of the selection circuitry while in the second mode of operation.

17. The touch panel system of claim 12, the measurement system further including a plurality of column integrators each having a first input, a second input and an output, the first input being electrically coupled with a corresponding one of the column electrodes.

18. The touch panel system of claim 17, the selection circuitry further including:

a third output electrically coupled with at least one row electrode of the plurality of row electrodes; and

a fourth output electrically coupled with the second input of at least one column integrator.

19. The touch panel system of claim 18, the selection circuitry further including a second selection circuit including:

a first multiplexer configured to;

ground the third output of the selection circuitry while in the second mode of operation, and

output the drive signal to the fourth output of the selection circuitry while in the first mode of operation; and

a second multiplexer configured to;

output the drive signal to the fourth output of the selection circuitry while in the second mode of operation, and

ground the third output of the selection circuitry while in the first mode of operation.