Yes I did see the same issue.
The coefficients from Richard's toolbox can not be applied into circuit without any change, even after scaling. I did have to rescale manually by myself before applied into the circuit for all modulators to be bounded in supply range.
But it took many times' simulation to obtain the final coefficients(switch to different sets every time). What is the better way to do it?
The problem with every Sigma-Delta is that all of them presents as certain integrator saturation probability. This probability becomes worst as you increase Full-Scale, modulator order, or reduce integrator swing range and the number of quantization levels. To make matters worse, the theoreticall model does have some weaknesses and does not model the real modulator with a 100% accuracy. In order to get good coefficients from Richard's toolbox your Sigma-Delta requirements should not be too hard to meet (keep Full-Scale low, do not use very high-order modulators etc.). Even if your requirements are not very demanding, the requirements you define in the toolbox should always be more demanding than what you really need, to increase the probability of generating good coefficients.
I would sugest you read some good book about the subject, if you have the time. I does really help to understand some of these things and why the toolbox doesn't work 100%.
Try to avoid changing the coefficients by trial and error. I did that too, and it took me a lot of time and the results were not so good. When possible, try to stick to mathematical methods, such as the toolbox, and use he tricks I told you to increase your chances of sucess.
The thing is, we are using toolbox because we don't need to go through the detailed analog filter process, but finally when all transistor-level is done we found the coefficients do not work! The trial/error process may be never successful!
I thought opamp is fine as I used it to get higher SNR before. Anyway here is the situation: Opamp has ~50dB gain, output with 1.2Vpp differential swing, 1-bit quantizer. Vref is 1.1V. It is feedforward, 4-order and with two local feedback for distributed zeros. OSR of 28 and target ~65db SNR for the ADC.
Still need to rescale after getting coefficients from toolbox.
If you would like to use Schreier's Toolbox, you need to read the following book at least.hi i want to design sigma delta ADC and start using delta sigma toolbox would you introduce me good document to start using this delsig toolbox ?
Thank you, you mean the part of the book relate to delta sigma toolbox? (appendix B)? do you have the e-book?If you would like to use Schreier's Toolbox, you need to read the following book at least.
https://www.amazon.com/Understandin...F8&qid=1355150691&sr=1-1&keywords=delta+sigma
No.Thank you, you mean the part of the book relate to delta sigma toolbox? (appendix B)?
No. I have hard cover book of this.do you have the e-book?
No.
Appendix-B is no more than an old version of "DSToolbox.pdf" which is included in up-to-date "delsig".
https://pub.maruzen.co.jp/book_magazine/support/analog_digital/AppendixB.pdf
No. I have hard cover book of this.
Again, if you would like to use Schreier's Toolbox, you need to read the following book at least.
https://www.amazon.com/Understandin...F8&qid=1355150691&sr=1-1&keywords=delta+sigma
Background theories required for Schreier's Toolbox are descripted in this book.
So purchase this book, if you would like to use Schreier's Toolbox.
Some useful but too simple materials might be available in the followings.
https://individual.utoronto.ca/schreier/ece1371.html
https://individual.utoronto.ca/schreier/ece1371-2012.html
Do you understand Delta-Sigma-ADC correctly ?I want to design Digital Sigma-Delta ADC to be implemented on FPGA,
does this toolbox help me to design the modulator part of my ADC?
as of course it should be in digital...
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