2BITS PER CIRCLE HIGH-SPEED SUCCESSIVE APPROXIMATION TYPE ANALOGUE-TO-DIGITAL CONVERTER

摘要

A 2bits per circle high-speed successive approximation type analogue-to-digital converter, comprising: a switch S2, sampling switches S1 and S3, capacitor arrays DAC1 and DAC2, comparators COMP1-COMP3, an encoding circuit, a switch array SW1 corresponding to the capacitor array DAC1, a switch array SW2 corresponding to the capacitor array DAC2, a shifting register and a digital correction unit. Compared with a successive approximation type analogue-to-digital converter having the traditional 1bit per circle structure, the analogue-to-digital converter has the advantage that a working speed thereof can be doubled; compared with a successive approximation type analogue-to-digital converter having the traditional 2bit per circle structure, the analogue-to-digital converter has the advantages that under the condition that a high-order large capacitor is not completely built, a successive approximation process is continuously carried out and no fault happens, and an error which is caused by not completely building a preceding-stage large capacitor is not needed to be compensated by adding a redundancy bit capacitor; and due to the existence of the encoding circuit, the conversion from a thermometer code to a binary code can be effectively realized, and inherent errors brought by comparators can be reduced by randomly gating three comparators.