Feedforward passive noise shaping successive approximation type analog-to-digital converter

Abstract

The invention discloses a feedforward passive noise shaping successive approximation type analog-to-digital converter. According to the invention, a noise shaping SARADC employs a passive filter circuit structure, so that the use of a multi-input comparator is avoided and thermal noises and kickback noises of the comparator are reduced; the DAC capacitor and the margin capacitor have no charge sharing during margin collection, so that an active circuit is not needed and thus the power consumption is reduced; meanwhile, because of the low bandwidth of the noise shaping ADC, signals which changeslowly or have a long resting period, such as biological signals or temperature signals, are acquired and converted in an application occasion, so that a logic structure of low-order priority judgment is also adopted in the SAR logic circuit, and the power consumption and the conversion period are further reduced.

Description

technical field [0001] The invention belongs to the field of integrated circuits, in particular to a feedforward passive noise shaping successive approximation analog-to-digital converter. Background technique [0002] In the past, many studies on analog-to-digital converters focused on improving the sampling rate and resolution. However, in many medical devices used to continuously monitor human vital signs, pulse, etc., or ADCs for environmental monitoring devices for temperature do not require the above-mentioned high performance , On the contrary, the ADC is required to have lower conversion power consumption. The activity of the signal collected in the above scene is low, and the activity of the signal can be expressed by dividing the change of the output code of each conversion by the dynamic range. In view of the low activity of these collected signals, the following types of methods have been proposed ADCs: [0003] Asynchronous event-driven (level-crossing) ADC, t...

AI Technical Summary

Problems solved by technology

At present, the existing noise-shaping SAR ADCs are mainly divided into two types of structures: CIFF (cascaded integrator and distributed feedforward) and EF (error feedback). Among them, the comparator circuit of the noise-shaping SAR ADC with the CIFF structure usually needs to add at least A pair of input transistors are used for the summing of the DAC voltage and the conversion headroom voltage, the extra transistor will introduce additional thermal noise and kickback noise

The noise-shaping SAR ADC of the EF structure that has appeared only needs a single-input pair comparator, but its disadvantage is that the charge sampled on the DAC capacitor will share the charge with the residual capacitor to cause attenuation, so when the residual capacitor is small, Active headroom amplifiers are required to boost the signal amplitude to produce a steep noise transfer function (NTF) curve to achieve the desired noise shaping effect

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