Foreground calibration circuit applicable to pipelined analog-digital converter and calibration method thereof

Abstract

The invention discloses a foreground calibration circuit applicable to a pipelined analog-digital converter and a calibration method thereof. The calibration circuit comprises an amplifier with a local positive feedback, a backward-stage analog-digital converter, a fixed analog input signal module, a constant module, a relay alignment and summation unit, an accumulative averager, a register, a summator, a subtractor, an n bit sub ADC, a sub ADC and a calibration state machine. According to the invention, the calibration circuit is simple in structure, the modification for the analog circuit is minor, addition, subtraction and shifting operations are carried out in the digital domain, the digital overhead is very low and the common problems of low convergence rate and high computation complexity during the background calibration are avoided. The foreground calibration method can improve the dynamic performance of the analog-digital converter, an operational amplifier can work in the maximum gain state, a capacitance mismatch error is figured out and the final output code is calibrated.

Description

technical field [0001] The invention relates to the technical field of integrated circuits, in particular to a foreground calibration circuit and calibration method applied to a pipelined analog-to-digital converter. Background technique [0002] With the rapid development of semiconductor technology, high-speed and high-precision analog-to-digital converters have been widely used in digital communications, military radar and other fields. As one of the mainstream ADC products at present, the pipeline analog-to-digital converter can well take into account the requirements of speed and precision. In the pipeline A / D converter, the power consumption of the op amp accounts for the main part. In order to reduce the requirements for the op amp, digital calibration methods are often used; capacitance mismatch is also a reason that restricts the performance of the A / D converter, so it is often necessary to simultaneously Calibrate op amp gain and capacitance mismatch. [0003] An...

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Problems solved by technology

[0003] An op amp with local positive feedback, because its output impedance can be close to infinity under ideal conditions, so it can achieve ultra-high gain at low power consumption and reduce the nonlinearity caused by limited gain, but the local positive feedback op amp The gain of the capacitor is often affected by the process, temperature and power supply voltage. If there is no adjustment function, the gain will not reach the ideal value; the matching accuracy of the capacitor is generally only about 10 bits in the CMOS process, and in order to reduce power consumption generally requires a small Capacitance value, so the matching accuracy is less than 10 bits, seriously reducing the accuracy of the pipelined analog-to-digital converter

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