Stable High-Order Delta–Sigma Digital-to-Analog Converters

Kiss, P.; Arias, J.; Li, D.; Boccuzzi, V.

doi:10.1109/tcsi.2003.821283

Cited by 33 publications

(21 citation statements)

References 19 publications

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“…However, the location of zeroes can be optimized such that the noise power in the band-of-interest can be minimized [22]. It has been shown in [41] that an (n − 1) th -order DSM with number of output bits, m = n can be always made stable i.e. no overflow in the integrator.…”

Section: Conventional Dsmsmentioning

confidence: 99%

Design of High-Speed Time-Interleaved Delta-Sigma D/A Converters

Bhide

2015

Linköping Studies in Science and Technology. Dissertations

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Digital-to-analog (D/A) converters (or DACs) are one the fundamental building blocks of wireless transmitters. In order to support the increasing demand for high-data-rate communication, a large bandwidth is required from the DAC. With the advances in CMOS scaling, there is an increasing trend of moving a large part of the transceiver functionality to the digital domain in order to reduce the analog complexity and allow easy reconfiguration for multiple radio standards. ∆Σ DACs can fit very well into this trend of digital architectures as they contain a large digital signal processing component and offer two advantages over the traditionally used Nyquist DACs. Firstly, the number of DAC unit current cells is reduced which relaxes their matching and output impedance requirements and secondly, the reconstruction filter order is reduced.Achieving a large bandwidth from ∆Σ DACs requires a very high operating frequency of many-GHz from the digital blocks due to the oversampling involved. This can be very challenging to achieve using conventional ∆Σ DAC architectures, even in nanometer CMOS processes. Time-interleaved ∆Σ (TIDSM) DACs have the potential of improving the bandwidth and sampling rate by relaxing the speed of the individual channels. However, they have received only some attention over the past decade and very few previous works been reported on this topic. Hence, the aim of this dissertation is to investigate architectural and circuit techniques that can further enhance the bandwidth and sampling rate of TIDSM DACs.The first work is an 8-GS/s interleaved ∆Σ DAC prototype IC with 200-MHz bandwidth implemented in 65-nm CMOS. The high sampling rate is achieved by a two-channel interleaved MASH 1-1 digital ∆Σ modulator with 3-bit output, resulting in a highly digital DAC with only seven current cells. Two-channel interleaving allows the use of a single clock for both the logic and the final multiplexing. This requires each channel to operate at half the sampling rate i.e. 4 GHz. This is enabled by a high-speed pipelined MASH structure with robust static logic. Measurement results from the prototype show that the DAC achieves 200-MHz bandwidth, −57-dBc IM3 and 26-dB SNDR, with a power consumption of 68-mW at 1-V digital and 1.2-V analog supplies. This architecture shows good potential for use in the transmitter baseband. While a good linearity is obtained from this DAC, the SNDR is found to iv be limited by the testing setup for sending high-speed digital data into the prototype.The performance of a two-channel interleaved ∆Σ DAC is found to be very sensitive to the duty-cycle of the half-rate clock. The second work analyzes this effect mathematically and presents a new closed-form expression for the SNDR loss of two-channel DACs due to the duty cycle error (DCE) for a noise transfer function (NTF) of (1 − z −1 ) n . It is shown that a low-order FIR filter after the modulator helps to mitigate this problem. A closed-form expression for the SNDR loss in the presence of this filter is also developed. The...

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Section: Conventional Dsmsmentioning

confidence: 99%

Design of High-Speed Time-Interleaved Delta-Sigma D/A Converters

Bhide

2015

Linköping Studies in Science and Technology. Dissertations

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“…Although it is shown in [18] that multi-bit quantization is nonlinear and has a limiting overloading level, the accurate prediction of the stability limits of multi-bit quantizer based Δ-Σ modulators still remains unresolved. A lower-bound has been established in [19] and [20], which however does not consider any of the statistical properties of the quantizer input and its effects on the quantizer gain. The statistical properties of the signal and quantization noise variance at the quantizer input simultaneously determine the quantizer gain.…”

Section: B Multi-bit Quantizersmentioning

confidence: 99%

“…Accordingly (17) is evaluated that gives the variation of  e with K q5L which for 0.153 is 1.027. One can then evaluate (20) which gives the value of  =4.050.…”

Section: B Step-by Step Experimental Validationmentioning

confidence: 99%

Nonlinear Stability Prediction of Multibit Delta–Sigma Modulators for Sinusoidal Inputs

Lota

Al-Janabi

Kale

2014

IEEE Trans. Instrum. Meas.

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“…2.3) has been determined by using the L 1 norm of the loop filter. A sufficient stability criterion of the EFM has been provided in [100] where an EFM with a truncator of q + 1 bits and an FIR loop filter H (z) (that contributes to a q-bit increase in the data-flow) is stable. The EFM is considered as "un-stable" if it produces a poor signal-to-noise ratio (SNR) compared to that predicted by the linear models, according to [100, Sec.…”

Section: Introductionmentioning

confidence: 99%

Complexity and Power Reduction in Digital Delta-Sigma Modulators

Afzal

2015

Linköping Studies in Science and Technology. Dissertations

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Papers A and C are reprinted with permission from IEEE.Cover figure is an illustration of the digital cascaded error-feedback modulator.Printed by LiU-Tryck, Linköping, Sweden 2014 To my parents and teachers AbstractA number of state-of-the-art low power consuming digital delta-sigma modulator (∆Σ) architectures for digital-to-analog converters (DAC) are presented in this thesis. In an oversampling ∆Σ DAC, the primary job of the modulator is to reduce the word length of the digital control signal to the DAC and spectrally shape the resulting quantization noise. Among the ∆Σ topologies, error-feedback modulators (EFM) are well suited for so called digital to digital modulation In order to meet the demands, various modifications to the conventional EFM architectures have been proposed. It is observed that if the internal and external digital signals of the EFM are not properly scaled then not only the design itself but also the signal processing blocks placed after it, may be over designed. In order to avoid the possible wastage of resources, a number of scaling criteria are derived. In this regard, the total number of signal levels of the EFM output is expressed in terms of the input scale, the order of modulation and the type of the loop filter.Further on, it is described that the architectural properties of a unit elementbased DAC allow us to move some of the digital processing of the EFM to the analog domain with no additional hardware cost. In order to exploit the architectural properties, digital circuitry of an arbitrary-ordered EFM is split into two parts: one producing the modulated output and another producing the filtered quantization noise. The part producing the modulated output is removed after representing the EFM output with a set of encoded signals. For both the conventional and the proposed EFM architectures, the DAC structure remains unchanged. Thus, savings are obtained since the bits to be converted are not accumulated in the digital domain but instead fed directly to the DAC.A strategy to reduce the hardware of conventional EFMs has been devised recently that uses multiple cascaded EFM units. We applied the similar approach but used several cascaded modified EFM units. The compatibility issues among the units (since the output of each proposed EFM is represented by the set of encoded signals) are resolved by a number of architectural modifications. The digital processing is distributed among each unit by splitting the primary input bus. It is shown that instead of cascading the EFM units, it is enough to cascade their loop filters only. This leads not only to area reduction but also to the reduction of power consumption and critical path.All of the designs are subjected to rigorous analysis and are described mathev vi Abstract matically. The estimates of area and power consumption are obtained after synthesizing the designs in a 65 nm standard cell library provided by the foundry. Populärvetenskaplig sammanfattning vii viiiPopulärvetenskaplig sammanfattning I denna avhandling presenteras e...

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Stable High-Order Delta–Sigma Digital-to-Analog Converters

Cited by 33 publications

References 19 publications

Design of High-Speed Time-Interleaved Delta-Sigma D/A Converters

Design of High-Speed Time-Interleaved Delta-Sigma D/A Converters

Nonlinear Stability Prediction of Multibit Delta–Sigma Modulators for Sinusoidal Inputs

Complexity and Power Reduction in Digital Delta-Sigma Modulators

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