Patent ID: 8508502
Filing Date: 2013-08-13
Classification: G06F,H03K

Abstract:
1. A capacitive touchscreen system, comprising: a touchscreen comprising a first plurality of electrically conductive drive traces and a second plurality of electrically conductive sense traces, mutual capacitances existing between the first and second pluralities of traces at locations where the first and second pluralities of traces intersect to form pixels, such mutual capacitances changing in the presence of one or more fingers or touch devices brought into proximity thereto; drive circuitry operably connected to the first plurality of drive traces; sense circuitry operably connected to the second plurality of sense traces and comprising charge acquisition circuitry, the sense circuitry being configured to sense the mutual capacitances along each of the second plurality of sense traces and to generate a plurality of sense voltages corresponding to the sense traces; a plurality of comparators configured to receive as inputs thereto a threshold voltage and the sense voltages, the comparators providing comparator output signals; an analog multiplexer having as a first input thereto the sense voltages; a plurality of logical AND gates configured to receive as inputs thereto the comparator output signals and to provide as outputs therefrom logical AND output signals, the AND output signals being inputs to a digital multiplexer operably connected to the outputs of the plurality of logical AND gates, the analog multiplexer receiving as a digital input thereto a digital output of the digital multiplexer; a first sum circuit configured to receive as an input thereto an output from the analog multiplexer and to provide as an output therefrom an analog-to-digital converter (ADC) reference voltage representing a sum of the sense voltages corresponding to at least one cluster of pixels associated with at least one sensed touch on the touchscreen; a second weighted sum circuit configured to receive as an input thereto the output from the analog multiplexer and to provide as an output therefrom an input to the ADC representing a weighted sum of the sense voltages corresponding to pixels of the cluster; wherein the outputs of the comparators and the AND gates represent at least one cluster of pixels corresponding to at least one sensed touch on the touchscreen, the output of the second weighted sum circuit represents a weighted sum of the sense voltages corresponding to pixels of the cluster, and the ADC generates as an output therefrom a position code corresponding to an interpolated location of the sensed finger or device touch.