高精度模数混合SAR ADC校准算法

A high precision hybrid analog⁃digital SAR ADC calibration algorithm

针对高速逐次逼近型模数转换器中的比较器失调和电容失配问题,设计一种模拟前端“粗”校准与数字后端“细”校准相结合的模数混合校准技术,对系统失调电压以及电容失配分别进行抵消、量化与补偿,从而在保证模数转换器采样速率的同时能够有效提高转换精度和信噪比。基于12位模数转换器对所提出的电路结构和校准算法进行了Matlab行为级建模仿真,算法校准后在80 MHz采样率下信噪失真比达到73.28 dB,有效位数11.88 bit,分别比校准前提高15.1dB与2.5 bit。

Since high⁃speed successive approximation analog⁃digital converters(ADCs)have to face comparator offset and capacitor mismatching,we propose a hybrid analog⁃to⁃digital calibration algorithm that uses a“rough”calibration in the analog front end and a“fine”calibration in the digital back end to cancel,quantify and compensate the system offset voltage and capacitor mismatching.This strategy intends to effectively improve the conversion accuracy and signal⁃to⁃noise ratio while ensure the sampling rate of the ADC.We apply the proposed algorithm and the circuit structure to a 12⁃bit analog⁃to⁃digital converter and simulate it on Matlab in the behavior⁃level.The results show that the signal⁃to⁃noise distortion ratio and the effective digits reach 73.28 dB and 11.88 bit at the 80 MHz sampling rate after calibration,15.1 dB and 2.5 bit higher than before calibration,respectively.