DETECTOR CIRCUIT AND DETECT METHOD OF A CAPACITIVE TOUCH PANEL
First Claim
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1. A detector circuit of a capacitive touch panel having a plurality of traces, the detector circuit comprising:
- a sample-and-hold circuit for sampling a trace voltage of a selected one of the plurality of traces to generate a sampled voltage;
a SAR and control circuit for providing a threshold digital code and a successive approximation digital code, and providing a pre-conversion signal when beginning to convert the sampled voltage;
a DAC for converting the threshold digital code into a threshold voltage or converting the successive approximation digital code into a comparison voltage;
a multiplexer connected between the SAR and control circuit and the DAC, for providing either the threshold digital code to the DAC in response to the pre-conversion signal, or the successive approximation digital code to the DAC at the other time; and
a comparator connected to the DAC and the sample-and-hold circuit for comparing the sampled voltage with the threshold voltage or the comparison voltage to generate a comparison result for the SAR and control circuit;
wherein if the sampled voltage is lower than the threshold voltage, the SAR and control circuit asserts an abortion signal to abort sensing of the selected trace;
otherwise, the SAR and control circuit carries out successive approximation on the trace voltage for the selected trace.
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Abstract
A detector circuit and detect method of a capacitive touch panel conditionally abort sensing of useless traces of the capacitive touch panel when the capacitive touch panel senses the traces thereof. For a selected trace, the trace voltage thereof is sampled to be compared with a threshold voltage. If the sampled voltage is lower than the threshold voltage, the sensing of this trace is aborted and thus the operation of the detector circuit is reduced to improve the performance of the capacitive touch panel.
32 Citations
5 Claims
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1. A detector circuit of a capacitive touch panel having a plurality of traces, the detector circuit comprising:
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a sample-and-hold circuit for sampling a trace voltage of a selected one of the plurality of traces to generate a sampled voltage; a SAR and control circuit for providing a threshold digital code and a successive approximation digital code, and providing a pre-conversion signal when beginning to convert the sampled voltage; a DAC for converting the threshold digital code into a threshold voltage or converting the successive approximation digital code into a comparison voltage; a multiplexer connected between the SAR and control circuit and the DAC, for providing either the threshold digital code to the DAC in response to the pre-conversion signal, or the successive approximation digital code to the DAC at the other time; and a comparator connected to the DAC and the sample-and-hold circuit for comparing the sampled voltage with the threshold voltage or the comparison voltage to generate a comparison result for the SAR and control circuit; wherein if the sampled voltage is lower than the threshold voltage, the SAR and control circuit asserts an abortion signal to abort sensing of the selected trace;
otherwise, the SAR and control circuit carries out successive approximation on the trace voltage for the selected trace.
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2. A detect method of a capacitive touch panel having a plurality of traces, the detect method comprising the steps of:
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(a) sampling a trace voltage of a selected one of the plurality of traces to generate a sampled voltage; (b) comparing the sampled voltage with a threshold voltage; (c) if the sampled voltage is lower than the threshold voltage, aborting sensing of the selected trace; and (d) if the sampled voltage is higher than the threshold voltage, carrying out successive approximation on the trace voltage for the selected trace. - View Dependent Claims (3, 4, 5)
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Specification