HIGH SPEED NOISE TOLERANT MULTI-TOUCH TOUCH DEVICE AND CONTROLLER THEREFOR

• US 20110163992A1
• Filed: 01/05/2010
• Published: 07/07/2011
• Est. Priority Date: 01/05/2010
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: CORDEIRO, Craig A., Rebeschi, Thomas J.
• Granted Patent: US 8,411,066 B2
• Time in Patent Office: Days
• US Class Current: 345/174
• CPC Class Codes: G06F 2203/04104 Multi-touch detection in digitiser, i.e. details about the simultaneous detection of a plurality of touching locations, e.g. multiple fingers or pen and finger
• CPC Class Codes: G06F 3/04182 Filtering of noise external to the device and not generated by digitiser components
• CPC Class Codes: G06F 3/0445 using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer
• 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-sensitive device includes a touch panel, a drive unit, a sense unit, and a measurement unit. A touch applied to a node of the panel changes a capacitive coupling between two electrodes (a drive electrode and a sense electrode) of the touch panel. The drive unit delivers a drive signal, which may comprise one or more drive pulses, to the drive electrode. The sense unit couples to the sense electrode, and generates a response signal that includes a differentiated representation of the drive signal, which is then fed through a resistor. The amplitude of the response signal is responsive to the capacitive coupling between the electrodes, and is measured to provide an indication of a touch at the node.

Claims

1. A circuit configured to detect the presence of an object in proximity to a first and a second electrode, the first electrode driven with a plurality of drive signals, and the second electrode carrying resultant drive signals ensuing from the drive signals on the first electrode capacitively coupling to the second electrode, the second electrode coupled to a sense circuit configured to generate, for each drive signal, a response signal comprising a differentiated representation of the drive signal, the response signal having an amplitude responsive to the capacitive coupling between the first electrode and the second electrode, the sense circuit further including a peak detector configured to provide a peak detector output representative of a maximum amplitude of the response signal, the peak detector comprising at least a capacitor and a diode, and wherein a resistor is disposed in the circuit between where the response signal is generated and the capacitor of the peak detector.

2. The circuit of claim 1, further comprising a measurement unit coupled to the peak detector, the measurement unit configured to receive peak detector output and therefrom provide signals indicative of the presence of the object in proximity to the first and second electrode.

3. The circuit of claim 2, wherein the peak detector further comprises a diode disposed between the capacitor and where the response signal is generated.

4. The circuit of claim 3, wherein the plurality of drive signals comprises a plurality of rectangle pulses.

5. The circuit of claim 2, further comprising a reset switch coupled to the capacitor of the peak detector, the reset switch configured to discharge the respective capacitor in response to a reset signal.

6. The circuit of claim 5, wherein the drive signal comprises a plurality of ramped pulses.

7. The circuit of claim 6, further comprising a display located in proximity to the first and second electrode, the display'"'"'s output responsive to signals from the measurement unit indicative of the presence of an object located in proximity to the first and second electrode.

8. The circuit of claim 6, wherein the measurement unit additionally includes a differential amplifier configured to reduce or eliminate common mode noise.

9. The circuit of claim 1, wherein the response signal is generated by circuitry that includes at least a differentiating amplifier, and wherein the differentiating amplifier includes a negative resistor feedback loop that includes a capacitor and a resistor in series, the capacitor and the resistor oriented in parallel with another resistor to stabilize loop response.