Super Audio CD: The Rich Report References, Delta-Sigma Converters

Sidebar 1: References, Delta-Sigma Converters

S. Norsworthy, R. Schreier, G. Temes, eds., Delta-Sigma Data Converters: Theory, Design, and Simulation, IEEE Press, 1997.

After 15 years of very active development that was covered only in journal articles and the occasional book chapter, here are the seminal texts from all the leaders in the field. Each chapter of Delta-Sigma Data Converters includes extensive references that I do not restate here.

Chapter 1 introduces the topic, including pattern noise, dead zones, limit cycles, and dynamic-range limitations. High-order structures are introduced. The problems with a two-level system are discussed; also explained is why higher-order systems like to have more than two level quantizers.

Chapter 2 is a very mathematical look at noise in delta modulators, with a detailed discussion of the failure of the analysis with respect to a 1-bit second-order (and higher) loop filter. Dither is examined in this chapter, and is the sole subject of Chapter 3.

Chapter 4 discusses the complex issues of stability of high-order delta-sigma modulators. Placement of transmission zeros is detailed, along with theoretical S/N ratio plots for a given oversampling ratio and order.

Chapter 5 discusses the design of higher-order single-bit systems. Practical methods of preventing idle-channel tones are discussed, as are the practical problems of making the system stable.

Chapter 6 looks at Cascaded (MASH) structures that produce multi-level outputs, and Chapter 8 discusses the design of multibit internal converters, including such methods of improving multibit DAC linearity as dynamic-element matching and randomization.

Chapter 10 discusses architecture tradeoffs for DACs. Issues of analog circuit design for ADCs are dealt with in Chapter 11, and Chapter 12 does the same for DACs, including the effects of clock jitter. Chapter 13 is about decimation and interpolation in delta-sigma conversion.

Stability and tones in DSMs has been a big topic of research. The references below postdate the text of Delta-Sigma Data Converters and are drawn from practical papers on audio delta-sigma converters. Papers on multibit digital/analog conversion that include discussion of why to choose multibit over single-bit are listed below:

Y. Matsuya, K. Uchimura, A. Iwata, T. Kaneko, "A 17-bit Oversampling D-to-A Oversampling Technology Using Multistage Noise Shaping," IEEE Journal of Solid-State Circuits, Vol.24 No.4 (August 1989), p.969. This is the original MASH paper from NTT that gave rise to all the Japanese DACs developed by Panasonic and Sony. It uses a PWM DAC to output the multibit signal from the MASH coder (MASH always produces multibits). This important paper is not often cited. (People tend to cite the MASH ADC paper by the same group instead.)

H. Schouwenaars, et al, "An Oversampled Multibit CMOS D/A Converter for Digital Audio with 115dB Dynamic Range," IEEE Journal of Solid-State Circuits, Vol.26 No.12 (December 1991), pp.1775-80. Philips invented the delta-sigma modulator in the 1960s, and were the first to apply it to CD players in its 1-bit form (switched-capacitor based). Crystal Semiconductor soon joined the fun. This paper shows that Philips was still in the lead in 1991, as they moved from single- to multibit. The group has not done any recent work, and Philips no longer has high-performance parts in the catalog. Don't ask me why they stopped competing.

T. Hamasaki, "A 3V, 22mW Multibit Current-Mode Sigma-Delta DAC with 100dB Dynamic Range," IEEE Journal of Solid-State Circuits, Vol.31 No.12 (December 1996), p.1888. This is the Burr-Brown work.

R. Adams, K. Nquyen, K. Sweetland, "A 113dB SNR Oversampling DAC with Segmented Noise-Shaped Scrambling," IEEE Journal of Solid-State Circuits, Vol.33 No.12 (December 1998), p.1871. This is the Analog Devices work, and a very clear paper that took the "Best Paper" prize when presented at IEEE ISSCC—about as prestigious a prize as you can get in the world of electronic engineering.

T. Shui, R. Schreier, F. Hudson, "Mismatch Shaping for a Current-Mode Multibit Delta-Sigma DAC," IEEE Journal of Solid-State Circuits, Vol.34 No.3 (March 1999), p.331. An important university paper with good references.

I. Fujimori, A. Nogi, T. Sugimoto, "A Multibit Delta-Sigma DAC with 120dB Dynamic Range," ISSCC Digest of Technical Papers, February 1999, pp.152-153. The AKM response to Analog Devices.

X. Gong, et al, "A 120dB Multibit SC Audio DAC with Second-Order Noise Shaping," ISCCC Digest of Technical Papers, February 2000, pp.344-345. The Crystal Semiconductor response to AKM and Analog Devices.—David Rich