Fully-differential adaptive gain control capacitor detection front-end circuit

Abstract

The invention discloses a fully-differential adaptive gain control capacitor detection front-end circuit, which is characterized in that a fully-differential switched capacitor (CV) conversion circuitis connected with a low-power-consumption adaptive gain control loop through a fully-differential variable gain amplifier, and the amplitude of common-mode voltage is adjusted by adjusting and controlling the magnitude of charging current, so that parasitic capacitance at two differential ends is counteracted. The method has the characteristics of low power consumption, high precision, high speedand large parasitic tolerance.

Description

technical field [0001] The invention belongs to the technical field of full-differential capacitance detection front-end circuits, and in particular relates to a full-differential self-adaptive gain control capacitance detection front-end circuit. Background technique [0002] Due to its many advantages, capacitive sensors play a very important role in information capture and are widely used. Compared with other sensors, it has the advantages of simple structure, high sensitivity, strong overload capacity, strong tolerance to parasitic, high precision, short dynamic response time, and strong adaptability to harsh conditions such as high temperature, radiation, and strong vibration. With the development and change of the measurement object of the capacitive sensor, the measured capacitance value of the capacitive sensor becomes pF, fF or even smaller. In most cases, the measured capacitance is smaller than the parasitic capacitance value, so a high dynamic range is required. ...

AI Technical Summary

Problems solved by technology

In the range of 1pF to 300pF, the effective precision of 16bits has been achieved, the power consumption of the front-end scheme has reached 1.4mA, and the circuit invention is relatively complicated; while the chip AD7147 invented by ADI uses a 16-bit Sigma-Delta ADC structure, reaching The fF-level resolution is guaranteed, and the full power consumption is guaranteed to be around 1mA, but the measurement range is not large enough, and the single detection time is long; the other uses the front-end capacitive-to-triangular wave solution, which can reach 1fF at 50pF resolution, but higher power consumption; there is also a C-V scheme based on switched capacitors, which is quantized by Sigma-Delta ADC and achieves an SNR of 98dB

Images