Digital Delta-Sigma DAC

Wikopedia has some good information. At least yesterday it did.

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Ayup. Of that's the way you spell ot.

:)

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Hi Randy,

You mean "Wikipedia" - replace the 'o' with an 'i'.

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Jim Thomas            Principal Applications Engineer  Bittware, Inc
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warning instead. - Brian Crane

In sci.electronics.basics Davy wrote: : Hi all,

: I want to design a digital delta-sigma DAC. It includes a pulse density : modulated module and RC low-pass filter.

: The pulse density modulated module is a Delta-Sigma type (one adder and : one substractor). But why use Delta-Sigma type (i.e. how to understand : it)? Is there any good tutorial on digital Delta-Sigma?

: Best regards, : Davy

Read, read, read!

In any A/D or D/A circuit there is a quantizer -- the part of the circuit that actually does the conversion from analog to digital. The error in quantization shows up as noise in the resulting signal. The total power of this quantization noise only depends upon the number of levels in the quantizer, for any type of data converter (This is often stated as the distance between levels, which means pretty much the same thing.)

In a nutshell, while most types of data converters result in quantization noise with a white spectrum (i.e. spread evenly throughout the signal band,) Delta-Sigma converters "shape" the noise, to move it out of the band of interest. This is often combined with oversampling which has at least two advantages -- to spread the quantization noise out over a larger band (even without noise shaping,) and to be able to move the quantization noise far away from the band of interest, such that it can be subsequently filtered out relatively easily.

Delta-Sigma modulation allowed for parctical A/D and D/A converters to be built that use as few as 2 levels (i.e. "1-bit converters") and have acceptable performance for data conversion of relatively low-bandwidth signals like audio (or slower) signals. The reason why Delta-Sigma converters are usually used for low-bandwidth signals is because the oversampling ratio must be relatively high (around 100X) for good performance, which dictates how fast the system clock needs to run.

Joe

Hi,

Thank you for your help!

I just want to learn the simplest one-bit Sigma Delta DAC.

And I found a link interesting:

I have one more question: If I want the one-bit Sigma Delta DAC have better performance, shall I accelerate the integrator (move the frequency Fs to higher frequency)?

Best regards, Davy

Hi,

If you want to understand more about internals of ADC/DAC with differentiation of various methods I will refer one book

It titles something like Designing Methods of ADC/DAC from an author named Joshpher...

I am very sorry that I am not able to give correct name of both book and author but what ever I knew I have told I had referred this book some time back.

But for delta sigma type of conversion you have to limit the data width also as you increase the data width for more resolution the noise will cause problems.

Thanks, Regards, Kedar

"Davy" skrev i en meddelelse news: snipped-for-privacy@g47g2000cwa.googlegroups.com...

I would recommend books from the authors Richard Schreier, Gabor C. Temes, Steven R. Norsworthy and James C. Candy. Specifically the following books cover almost all subjects from end to other:

R. Schreier, G. Temes, "Understanding Delta-Sigma Data Converters", 2004

Very good introduction to the principles, with many examples. A more hands-on approach than many other books on the subject.

R. Schreier, G. Temes, S. Norsworthy "Delta Sigma Data Converters: Theory, Design and Simulation", 1996

Very detailed and in-depth coverage with good theoretical background on most subjects.

James C. Candy, Gabor C. Temes, "Oversampling Delta-Sigma Data Converters: Theory, Design and Simulation", 1991

A collection of important scientific papers that covers the full (almost) history of the development of this particular field of science. Very good supplement for the two other books.

I have read several other books on the subject, but none of them have the accuracy of these books. I would recommend not reading them cronologically, but start with the newest one, and then progress to the older books if you have a need for more background info or explanation of the theories.

-Thomas

In sci.electronics.basics Davy wrote: : Hi,

: Thank you for your help!

: I just want to learn the simplest one-bit Sigma Delta DAC.

: And I found a link interesting: :

: I have one more question: : If I want the one-bit Sigma Delta DAC have better performance, shall I : accelerate the integrator (move the frequency Fs to higher frequency)?

: Best regards, : Davy

Yes, that is one way to achieve slightly higher performance.

Joe

You can read the presentation I made at the comp.dsp conference on delta sigma conversion here:

See especially Figure 9 on page 18, which shows how SNR is related to modulator order and oversampling ratio.

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