A fully differential microcapacitance detection chip with strong anti-interference and ultra-low power consumption

Abstract

The present invention proposes a fully differential microcapacitance detection chip with strong anti-interference and ultra-low power consumption. By setting a phase-locked synchronous sample holder, the inherent switching noise caused by system design can be suppressed; the fully differential structure reduces the temperature of the amplifier. Conversion noise caused by drift and bias interference; at the same time, the aperture time of the A / D converter is reduced, the accuracy of the A / D converter is improved and the inaccuracy of the conversion time is eliminated; almost all high-frequency harmonics can be filtered component, to obtain a stable DC component, it is not necessary to install an LPF or a phase-sensitive demodulation unit after the capacitor-voltage conversion circuit to obtain a stable DC waveform, thereby avoiding the largest source of systematic noise, cost, power consumption, and transmission Latency has a great advantage.

Description

technical field [0001] The invention relates to the field of micro-capacitance detection, in particular to a micro-capacitance detection chip with strong anti-interference and ultra-low power consumption with a fully differential structure. Background technique [0002] Due to sensor manufacturing process and cost considerations, the capacitance value applied to strain sensing is very small (about 1-10pf), and the capacitance change due to strain force is even smaller (about 0.01-2pf), so extremely precise Detection technology to ensure the accuracy and sensitivity of data. The main idea of ​​high-precision capacitance detection is to convert the capacitance change into a voltage or current signal that is easy to measure, and then detect the change of the signal through the voltage or current signal amplification circuit. Generally, three methods of switching capacitors, relaxation oscillation, and charge amplification are used in the sensor chip. The result of the relaxat...

AI Technical Summary

Problems solved by technology

The result of the relaxation oscillation circuit is simple. When the capacitance to be measured is below 100pF, the inter-board capacitance often affects the measurement results, and the anti-interference ability is poor. In addition, in the process of measuring tiny capacitance, it is more easily affected by noise, and the test accuracy is also poor. There are big challenges

Both the charge amplification method and the switched capacitor method can suppress the influence of stray capacitance and improve the accuracy, but both of them face two major technical problems: First, the theoretical basis of these two technologies is to complete a capacitor through the switching circuit. Charge and discharge process, so as to measure the charge capacity

Due to the charge-injection effect of the mos tube, the measurement will produce a pF-level error

Both, these two technologies convert the capacitance value into a DC voltage and amplify it for measurement, resulting in the temperature-sensitive zero-point drift problem of the amplifier

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