Capacitance measurement circuit and measurement method based on analog-to-digital converter

Abstract

The invention provides a capacitance measurement circuit and measurement method based on an analog-to-digital converter, which can realize low power consumption and high precision so as to improve theprecision of capacitance measurement, and the circuit comprises an analog front-end module, an analog-to-digital converter, a digital control module, a decimation filter module and a reference voltage module, the input end of the analog front-end module is connected with a capacitor to be tested, residual voltage is obtained through sampling and conversion, and the residual voltage is output to the analog-to-digital converter. The circuit is characterized in that a noise shaping successive approximation type analog-to-digital converter is adopted as an analog-to-digital converter, oversampling and analog-to-digital conversion are carried out on residual voltage, and generated oversampling digital code streams are output to a decimation filter module; the decimation filter module performsfrequency reduction and low-pass filtering on the oversampled digital code stream to obtain a final analog-to-digital converter output digital code; the final capacitance measurement output value is the sum of the compensation capacitance value in the analog front-end module and the digital code output by the analog-to-digital converter.

Description

technical field [0001] The invention relates to the technical field of capacitance measurement, in particular to a capacitance measurement circuit and measurement method based on an analog-to-digital converter. Background technique [0002] Nowadays, the touch screen capacitance of many smart devices is a self-capacitance type, that is, one end of the measured capacitance is fixedly grounded. The capacitance values ​​of these capacitors need to be measured. In the prior art, a capacitance-to-digital converter is generally used to measure these self-capacitances. An important component in the capacitance measurement circuit of the capacitance test converter is the analog-to-digital converter. [0003] Smart devices have high requirements on their own power consumption, so the design of the capacitance measurement circuit not only requires high capacitance measurement accuracy, but also requires low power consumption. [0004] Therefore, in the prior art, successive approxi...

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Problems solved by technology

[0005] Aiming at the problem that the successive approximation analog-to-digital converter in the existing capacitance measurement circuit cannot realize high-precision sampling while satisfying low power consumption, this application provides a capacitance measurement circuit based on an analog-to-digital converter, which It can solve the above problems and realize low power consumption and high-precision sampling at the same time, thereby improving the accuracy of capacitance measurement

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