Sigma Delta ICs

[d1983]

I was curious if any of you knew of any Sigma-Delta chips that would have an output of the sigma-delta modulated signal rather than a 2's compliment serial out. Or, am I best off to try and design up my own?
Thanks!

 

[fdeck]

It's not a chip, but Tekko has it here:

http://www.diyaudio.com/forums/showthread.php?s=&threadid=109844

Remove the "power output" stage, and you've got a basic sigma delta.

Remove the flip-flop and it is a self-oscillating Class D.

 

[phase_accurate]

Designing a sigma-delta loop is not that difficult in theory but practical implementation can be a PITA.

There was once a two-chip delta sigma ADC by Burr-Brown that consisted of the delta-sigma modulator/converter and the decimation filter in two seperate ICs. But the delta-sigma converter was 4 bit - I guess that you are looking for a one-bit solution, don't you ?

Regards

Charles

 

[d1983]

Yeah. A one bit stream is really what I'm looking for.
Thanks for the point to the post though. I thought I'd looked through just about all the posts here.

 

[phase_accurate]

Since you are a student of engineering you probably have access to the JAES, have you ?

There was an interesting article in Vol 52 March 2004 of the JAES called: "One-Bit audio: An Overview"

This is a good article to give you some basic understanding of DS modulators.

Regards

Charles

 

[phase_accurate]

And here is a nice paper by Bruno Putzeys showing some interesting design -details/-decisions of a practical implementation of a high quality audio ADC :

http://www.grimmaudio.com/whitepapers/discrete ad converter.pdf

Regards

Charles

 

[d1983]

I just re-read my post and realized that it sounded sort of.... abrupt.
I read through that thread and it was amazingly helpful, I haven't noticed it before.
And I am looking for a single bit stream. I've started plugging away in OrCAD to try and design one up.
If anyone has any hints about designing the integrator or choosing components I'd love to hear about them, or even if I could be pointed towards another good thread or site that'd be great!
Thanks everyone for your help.

 

[phase_accurate]

What I could offer you is a simulation model for a DS amp with fourth order loop and a 8 Ms/s sampling rate.

It uses just basic models like voltage controlled voltage sources.

If this is of any help let me know.

Regards

Charles

 

[d1983]

phase_accurate :
That would be so great! I would definitely appreciate that! would you like to email it to me, or what's best?

 

[Gorilla]

Analog's AD7400 or AD7401 output a raw 2nd order stream.

The 16-bit rating they are given is from AFAIK the decimation filter they use for performance analysis in the datasheet.

 

[phase_accurate]

If others are interested as well I might post it here. If not - then PM me so I can send you the .sch file.

Regards

Charles

 

[Gorilla]

Charles, I would be interested too. Thanks.