Correction circuit for offset voltage of SAR_ADC system, and correction method based on correction circuit

Abstract

The invention discloses a correction circuit for an offset voltage of an SAR_ADC system, and a correction method based on the correction circuit. The correction circuit comprises a PGA module, an input control module, a coding correction control module, and a differential comparator module, wherein the input control module is connected with the PGA module, and is used for controlling a signal of acorrection signal source input end to be output to the PGA module; the differential comparator module is used for adjusting capacitances of a first adjustable capacitor and a second adjustable capacitor so as to correct the offset voltage of the SAR_ADC system, and updating a comparison judgment result obtained by an output end; and the coding correction control module is used for obtaining corresponding complementary coding signals for adjusting the capacitances of the first adjustable capacitor and the second adjustable capacitor according to the comparison judgment result output by the differential comparator module, and does not stop a correction process until two continuous conversions between a high level and a low level are carried out at the output end of the differential comparator module. The overall circuit is easy to implement, and the correction precision is high.

Description

Technical field [0001] The invention relates to the technical field of analog-to-digital conversion, in particular to a correction circuit and a correction method for the offset voltage of the SAR_ADC system. Background technique [0002] Successive approximation register analog to digital converters (SAR_ADC for short) is a common analog to digital conversion structure for medium to high resolution applications. The traditional SAR_ADC system such as figure 1 As shown, SAR_ADC includes a comparator, a DAC module, a holding circuit and a logic control circuit. Among them, the DAC module includes a capacitor array or a mixed array of capacitor resistors, whose function is to generate a corresponding analog voltage to the comparator under a specific digital code value input condition; the comparator has a differential comparator with N+1 bit resolution; logic control The circuit generates the corresponding N-bit digital code value D0[N-1:0] according to the comparator to the DAC m...

AI Technical Summary

Problems solved by technology

However, due to various factors such as the offset of the comparator itself, the imbalance between the internal ground of the SAR_ADC chip and the ground of the PCB board, the mismatch of the capacitor, and the irrational factors of the MOS tube switch, the SAR_ADC’s ​​offset is caused, resulting in a certain range. The measured signal cannot be effectively measured by the ADC, so that there is a corresponding error in the digital signal output by SAR_ADC

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