DUAL-MODE CAPACITANCE SENSING IN A TOUCH PANEL SENSOR

• US 20140145997A1
• Filed: 11/26/2012
• Published: 05/29/2014
• Est. Priority Date: 11/26/2012
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Maxim Integrated Products, Inc. (Analog Devices, Inc.)
• Inventors: Tiruvuru, Rajesh
• Granted Patent: US 9,582,123 B2
• Time in Patent Office: Days
• US Class Current: 345/174
• 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 configured to detect a change in capacitance associated with a touch event upon a touch panel;

a measuring component coupled to the sensor, 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 coupled to the sensor and to the measuring component, 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 selection component, the driver component configured to generate a drive signal, the drive signal furnished to the sensor during the first mode of operation and to the measuring module during the second mode of operation,

wherein the drive signal includes a first amplitude characteristic during the first mode of operation and includes a second amplitude characteristic during the second mode of operation, the second amplitude characteristic different from the first amplitude characteristic.

2. The system as recited in claim 1, wherein the measuring component comprises a plurality of integrators, each integrator of the plurality of integrators including 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 selection component comprises a first multiplexer and a second multiplexer, wherein the first multiplexer is coupled to the sensor and the second multiplexer is coupled to the measuring component.

9. A system comprising:

a sensor configured to detect a change in capacitance associated with a touch event upon a touch panel;

a measuring component coupled to the sensor, 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 coupled to the sensor and to the measuring component, 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;

a driver component coupled to the selection component, the driver component configured to generate a drive signal, the drive signal furnished to the sensor during the first mode of operation and to the measuring module during the second mode of operation; and

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

wherein the drive signal includes a first amplitude characteristic during the first mode of operation and includes a second amplitude characteristic during the second mode of operation, the second amplitude characteristic different from the first amplitude characteristic.

10. The system as recited in claim 9, wherein the measuring component comprises a plurality of integrators, each integrator of the plurality of integrators including 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.

11. The system as recited in claim 9, wherein the driver component comprises a digital-to-analog converter coupled to a buffer, the buffer coupled to the sensor.

12. The system as recited in claim 9, 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.

13. The system as recited in claim 12, wherein the demodulator component comprises an analog-to-digital converter.

14. The system as recited in claim 9, 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.

15. The system as recited in claim 9, wherein the selection component comprises a first multiplexer and a second multiplexer, wherein the first multiplexer is coupled to the sensor and the second multiplexer is coupled to the measuring component.

16. The system as recited in claim 9, wherein the second amplitude characteristic is at least approximately ten times smaller than the first amplitude characteristic.

17. A method comprising:

causing issuance of a selection signal to a selection component to cause selection of a first mode of operation to measure mutual-capacitance associated with a sensor or a second mode of operation to measure self-capacitance associated with the sensor, the sensor configured to detect a change in capacitance associated with a touch event upon a touch panel;

adjusting an offset cancellation capacitance furnished by an offset component until the offset cancellation capacitance at least approximately equals a capacitance associated with a drive channel and the sensor to at least partially cancel the capacitance associated with the drive channel and the sensor;

adjusting a phase of a first signal to at least approximately one hundred and eighty degrees (180°

) of a phase of a second signal to at least partially cancel the second signal, the first signal generated by an offset cancellation driver component and the second signal generated by a sensor driver component of the drive channel; and

adjusting an amplitude of the first signal to equal at least a portion of an amplitude of the second signal to at least partially cancel a remaining portion of the second signal, the remaining portion of the second signal including a portion of the second signal not cancelled by the adjustment of the phase of the first signal.

18. The method as recited in claim 17, further comprising measuring at a measuring component the change in mutual-capacitance associated with the touch event during the first mode of operation and the self-capacitance associated with the touch event during the second mode of operation.

19. The method as recited in claim 17, wherein at least one of the sensor driver component or the offset cancellation driver component is a digital-to-analog converter.

20. The method as recited in claim 17, wherein the measuring component comprises a plurality of integrators, each integrator of the plurality of integrators coupled to a corresponding driving line and sensing line of the sensor.