High-precision calibrating device for SAR-type ADC

Abstract

The invention discloses a high-precision calibrating device for an SAR-type ADC. The high-precision calibrating device comprises a comparator. A high-level capacitor array and a low-level capacitor level are successively connected between the negative-direction input end and the positive-direction input end of the comparator. The high-level capacitor array is connected with a high-level and offset error calibrating module. The low-level capacitor array is connected with a low-level and bridging capacitance calibrating module. The high-level capacitor array and the low-level capacitor array controls conduction to a digital control logic through a switch array, wherein the switch array is connected through a refp / refn mode. The high-level and offset error calibrating module comprises a first gain capacitor. An offset error calibrating unit is parallelly connected with a plurality of high-level capacitance calibrating units. A first gain capacitor is connected with the offset error calibrating unit. The low-level and bridging capacitance calibrating module comprises a second gain capacitor. The second gain capacitor is connected with a low-level calibrating unit. The high-precision calibrating device can perform comprehensive calibration on a capacitor matching error, an error caused by parasitic capacitance, and a bridging capacitor precision error, and greatly improving integral conversion precision of the ADC.

Description

technical field [0001] The invention belongs to the technical field of ADC (analog-to-digital converter) high-precision calibration; in particular, it relates to a high-precision calibration device of a SAR (lifting successive approximation) type ADC. Background technique [0002] ADC is widely used in military and civilian fields as a bridge between analog and digital. As an important ADC configuration, SAR ADC is widely used in portable devices, aerospace devices and other fields due to its advantages of simple structure, low power consumption, and small area. A typical SAR ADC includes: comparators, switched capacitor arrays, bridge capacitors, redundant capacitors, sample and hold control switches and digital logic. Its working process is that in the high potential stage of the switching sequence, the ADC works in the sampling stage, and the switched capacitor array is connected to the input Vin; in the low potential stage of the switching sequence, the ADC works in the...

AI Technical Summary

Problems solved by technology

However, compared with the unit capacitance of the capacitor array, the bridge capacitor is a fractional capacitor, and the accuracy requirement is extremely high, which is prone to errors, resulting in a decrease in the overall accuracy of the ADC.

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