Browsing by Subject "Successive approximation register"
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Item A 12-bit, 10 Msps two stage SAR-based pipeline ADC(2012-12) Gandara, Miguel Francisco; Sun, Nan; Gharpurey, RanjitThe market for battery powered communications devices has grown significantly in recent years. These devices require a large number of analog to digital converters (ADCs) to transform wireless and other physical data into the digital signals required for digital signal processing elements and micro-processors. For these applications, power efficiency and accuracy are of the utmost importance. Successive approximation register (SAR) ADCs are frequently used in power constrained applications, but their main limitation is their low sampling rate. In this work, a two stage pipelined ADC is presented that attempts to mitigate some of the sampling rate limitations of a SAR while maintaining its power and resolution advantages. Special techniques are used to reduce the overall sampling capacitance required in both SAR stages and to increase the linearity of the multiplying digital to analog converter (MDAC) output. The SAR sampling network, control logic, and MDAC blocks are completely implemented. Ideal components were used for the clocking, comparators, and switches. At the end of this design, a figure of merit of 51 fJ/conversion-step was achieved.Item Digital enhancement techniques for data converters in scaled CMOS technologies(2015-12) Sanyal, Arindam; Sun, Nan; Viswanathan, TR; Orshansky, Michael; Hall, Neal; Yan, ShouliThis thesis presents digital enhancement techniques for data converters in advanced technology nodes. With technology scaling, traditional voltage-domain (VD) analog-to-digital converters (ADCs) face two major challenges: (1) reduction of dynamic range due to supply voltage scaling, and (2) decrease in intrinsic gain of transistors which makes high gain amplifier design tough. To address these challenges, a two-stage ADC architecture is presented which uses time-domain quantization to exploit the advantages of technology scaling. The architecture, consisting of a first stage successive approximation register (SAR) and a second stage ring oscillator, is highly digital and scaling friendly. Two prototypes have been developed to validate the proposed architecture. The 40nm CMOS prototype achieves 75.7 dB dynamic range at an excellent Schreier figure-of-merit of 172.2 dB. The proposed architecture has been extended to a capacitance-to-digital converter and a prototype has been developed in 40nm CMOS. The prototype can sense capacitances with a resolution of 1.3fF and has a Walden figure-of-merit of 60 fJ/step which is more than two times better than the current state-of-the-art. This thesis also presents digital techniques to improve performance of continuous-time(CT), delta-sigma digital-to-analog converters (DACs). Recently, CT delta-sigma DACs have received more attention than their discrete, switched-capacitor counterpart mainly because of low power and/or higher speed of operation. However, a critical disadvantage of CT, delta-sigma DACs is their greatly increased sensitivity to inter-symbol interference (ISI) error. To address this shortcoming of CT DACs, this thesis presents several algorithms that can mitigate ISI error simultaneously with static mismatch error. Further, the proposed algorithms are fully digital in nature and as such, are best poised to take maximum advantage of technology scaling. Thus, the techniques presented in this thesis will be important enabling factors in raising the envelope of performance of CT delta-sigma DACs in advanced technology nodes.