A sensor offset calibration method

Abstract

A sensor offset calibration method belongs to the technical field of analog integrated circuits. Based on the calibration system composed of coarse calibration module, fine calibration module, ADC and logic module, the final coarse calibration code and fine calibration code are generated through multiple coarse calibration and fine calibration, wherein the offset voltage to be calibrated is The output code of the ADC is obtained through the calibration system, and the output code of the ADC obtained each time is fed back to the calibration system to obtain a more accurate coarse calibration code and fine calibration code through the logic module to generate each coarse calibration code and fine calibration code; finally The calibration offset voltage is obtained according to the final coarse calibration code and the fine calibration code, and the offset voltage calibration is completed by subtracting the generated calibration offset voltage from the offset voltage to be calibrated. The invention can effectively eliminate the offset voltage, improve the system precision, and can be applied to the readout circuit of the pressure sensor.

Description

technical field [0001] The invention belongs to the technical field of analog integrated circuits, and in particular relates to a sensor offset calibration method, which can be applied to a pressure sensor readout circuit. Background technique [0002] Traditional pressure sensors are usually piezoresistive structures, such as figure 1 Shown is a typical Wheatstone bridge. Each row has a series structure composed of two series resistors. The two ends of the series structure are respectively connected to the power supply voltage AVDD and the power supply ground GND. The voltage Va or Vb between two resistors is a common mode voltage, and the voltage value between two resistors in two adjacent rows is also the same. which is: [0003] [0004] When the sensor is subjected to external pressure, under the action of the pressure, the resistance value of the pressured resistor will change, and different pressures will cause the resistance value of the resistor to change in di...

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Problems solved by technology

[0005] However, this structure has a very serious misalignment problem. Due to the limitation of the process, it is difficult for the resistors to be strictly equal in size, and there is usually a certain mismatch, so that there is still a gap between Va and Vb when there is no pressure. The voltage difference, that is, the offset voltage

If the mismatch is large, it may cause the offset voltage to directly overwhelm the voltage value signal containing the pressure information; or because the readout circuit needs to be amplified, the offset voltage will participate in the amplification, which will cause the op amp to be distorted or the ADC input to reach full output. Bias, cannot be quantified normally, so the offset voltage must be calibrated

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