Circuit for capacitive touch applications
First Claim
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1. A circuit for capacitive touch applications comprising:
- a charge integrator;
a low pass-filter and a correlated double sampler sharing a common capacitor, the common capacitor acting as an input capacitor to the correlated double sampler and as a filtering capacitor to the low pass-filter;
a sampler and holder;
an analog-to-digital converter (ADC) comprising a multistage switched capacitor analog-to-digital converter having a first stage and further stages, said first stage comprising a successive approximation register and a feedback digital-to-analog converter (DAC), wherein said sampler and holder is integrated in said first stage of said analog-to-digital converter, and wherein an amplifier is shared between said sampler and holder and said first stage of said analog-to-digital converter;
said low pass-filter having a cut-off frequency lower than the Nyquist frequency of the sampler and holder; and
said low pass filter comprising said input capacitor and a serial resistor.
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Abstract
A circuit for capacitive touch applications has a charge integrator, a low pass-filter, and a correlated double sampler having an input capacitor. The circuit also includes a sampler and holder, and an analog to digital converter. The low pass-filter has a cut-off frequency lower than the Nyquist frequency of the sampler and holder, and the low pass filter includes input capacitor and a serial resistor.
26 Citations
13 Claims
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1. A circuit for capacitive touch applications comprising:
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a charge integrator; a low pass-filter and a correlated double sampler sharing a common capacitor, the common capacitor acting as an input capacitor to the correlated double sampler and as a filtering capacitor to the low pass-filter; a sampler and holder; an analog-to-digital converter (ADC) comprising a multistage switched capacitor analog-to-digital converter having a first stage and further stages, said first stage comprising a successive approximation register and a feedback digital-to-analog converter (DAC), wherein said sampler and holder is integrated in said first stage of said analog-to-digital converter, and wherein an amplifier is shared between said sampler and holder and said first stage of said analog-to-digital converter; said low pass-filter having a cut-off frequency lower than the Nyquist frequency of the sampler and holder; and said low pass filter comprising said input capacitor and a serial resistor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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Specification