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Switched capacitor circuits

a technology of switching capacitors and capacitors, applied in the direction of pulse circuits, pulse techniques, code conversion, etc., can solve the problems of slowing down the conversion speed, more difficult to drive the capacitors by analog front ends, and reducing the noise of the capacitors.

Active Publication Date: 2021-08-05
ANALOG DEVICES INT UNLTD
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

One of the main problems in precision converters is the sampling noise of a capacitive digital-to-analog converter (DAC).
This detrimental aspect is due mainly to the increased size of the capacitor making it more difficult to drive the capacitor by an analog front end.
In addition, the increased size of the capacitor slows down the conversion speed.
That is, large capacitors are difficult to drive, occupy large area, and slow down conversion speed.
As CMOS technology is scaling, the reference voltage is also dropping, which forces the designer to further increase the size of the sampling capacitors.

Method used

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  • Switched capacitor circuits
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Embodiment Construction

[0020]The following provides a discussion of example embodiments of switched capacitor circuits, in accordance with the teachings herein. Such switched capacitor circuits illustrate architectures that provide methods of removing sampling noise in charge redistribution circuits. Such charge redistribution circuits can include, but are not limited to, analog-to-digital converters. In various embodiments, a tracking and synchronous sampling mechanism of thermal noise generated by a band-limiting resistor and sampling switches can be used to achieve a reduction of the noise sampled on an input capacitor.

[0021]FIG. 1 illustrates an approach to a two-stage-pipeline analog-to-digital converter (ADC). The approach can be extended to more than two stages. A pipeline or multi-stage capacitive charge redistribution ADC operates in two phases, where one phase is an acquisition phase and the other phase is a conversion and residue amplification phase. During the acquisition phase, selected ones ...

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Abstract

A device having a capacitive sampling structure that allows for removal of sampling noise can be implemented in a variety of applications. Noise cancellation can be achieved by storing on an auto-zero capacitor a scaled replica of kT / C noise by a mechanism of correlated sampling. In an example embodiment, a set of switches can be arranged such that, in switching, scaled thermal noise, generated in an acquisition phase in which a voltage signal is input to an input capacitor structure, is captured on an output capacitor structure and, in a conversion phase, the captured thermal noise is cancelled or compensated from an output of the output capacitor structure.

Description

FIELD OF THE DISCLOSURE[0001]This document relates to switched capacitor circuits and in particular to removing sampling noise in switched capacitor-amplifier circuits.BACKGROUND[0002]One of the main problems in precision converters is the sampling noise of a capacitive digital-to-analog converter (DAC). During an acquisition phase, the sampling structure exhibits a noise with a root mean square (RMS) value equal tokTC,produced by resistors connected in series with a capacitor. In the noise expression, k is Boltzmann's constant, T is the absolute temperature, and C is the value of the sampling capacitor. It can be seen, from the above relation, that in order to reduce the acquisition noise, the size of the input capacitor can be increased to levels which make the kT / C noise tolerable, which is detrimental. This detrimental aspect is due mainly to the increased size of the capacitor making it more difficult to drive the capacitor by an analog front end. In addition, the increased siz...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): H03M1/08H03F3/00H03K5/24
CPCH03M1/08H03F2200/372H03K5/24H03F3/005H03K17/687H03F3/45475H03F2203/45514H03M1/468H03M1/44H03M1/0626H03M1/66H03M1/06H03M1/00H03M1/10H03M1/12
Inventor BODNAR, RARES ANDREIDELIZIA, PASQUALE
Owner ANALOG DEVICES INT UNLTD