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System and method for sensing touches in capacitive panels

  • US 9,946,418 B2
  • Filed: 10/08/2015
  • Issued: 04/17/2018
  • Est. Priority Date: 10/08/2014
  • Status: Active Grant
First Claim
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1. A multi-touch sensing system for estimating a location of at least one touch point, the multi-touch sensing system comprising:

  • a panel;

    a grid of conductor disposed on the panel, the grid of conductor configured to provide capacitances between rows and columns of the grid;

    a driver array connected to the grid, the driver array configured to transmit a set of overlapping and independent row drive signals to the grid;

    a receiver array connected to the grid for receiving column signals from the grid via a plurality of inputs, the receiver array configured to;

    sense a pre-charge voltage on a differential pair of inputs selected from the plurality of inputs;

    pre-charge the plurality of inputs to increase a voltage detection accuracy;

    pre-charge the plurality of inputs between sampling times to substantially equalize a common-mode input to a differential input;

    equalize a differential mode for the differential pair of inputs by returning the differential pair of inputs to the pre-charge voltage and reducing slow drifting due to slowly changing offsets; and

    produce digital estimates of the column signals;

    a signal processing system in communication with the driver array and the receiver array, the signal processing system configured to estimate a coupling capacitance between the columns and the rows by correlating the digital estimates of the column signals with the independent row drive signals; and

    a controller for transforming the coupling capacitance into touch co-ordinates by detecting and extracting potential touches from raw differential data collected from the panel.

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