Switched-current delta-sigma A/D converters

Abstract

Switched-current oversampling A/D converters are the ideal choice for mixed analog/digital design due to their complete compatibility with digital CMOS process and high tolerance to process variation. This paper presents a tutorial discussion on all the aspects of switched-current oversampling A/D converters, including structures, circuits, and practical issues. Three different modulator structures and six different types of switchedcurrent circuits were used with an emphasis on low-voltage operation. Eight 3.3-V oversampling A/D converters were implemented and measured, and another one 1.2-V oversampling A/D converter was also implemented but yet to be measured.

A novel current-mode multi-channel integrating ADC

“…Many types of current-mode ADCs have been designed to support different requirements including sigma delta [2], folding and interpolating [3], flash ADCs [4], successive approximation [5], and algorithmic and pipelined architectures [6]. Selecting an architecture is important since each ADC architecture has specific advantages with respect to sampling rate, noise, resolution, dynamic range, power consumption, and implementation area.…”

Integrating ADC using a single transistor as integrator and amplifier for very low (1 fA minimum) input currents

“…Current-mode circuits on the other hand feature inherent large dynamic range independent of the supply voltage. Several ADC designs in the currentmode domain with supply voltages below 2 V have been reported [1].…”

Switched-current ΣΔ modulator for baseband channel applications

“…By eliminating 9312 we uncorrelate the settling of the quantizer from the signal fed in the second modulator stage. Furthermore, the above choice of coefficients permits to scale down the bias current of the second integrator and those in the next stage [6].…”

“…Although some switched-current EA modulators have appeared in the literature [6], [7] they were either of low order or worked with relatively low sampling frequencies. So far, there has not been an attempt to target high bandwidth applications such as the baseband channel conversion in wireless receivers.…”