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Design >> Analog Design >> How to achieve a high SNDR single-ended delta-sigma modulator?
https://designers-guide.org/forum/YaBB.pl?num=1530108152

Message started by Jacki on Jun 27^th, 2018, 7:02am

Title: How to achieve a high SNDR single-ended delta-sigma modulator?
Post by Jacki on Jun 27^th, 2018, 7:02am

Hello,

Due to my limited knowledge, I see most of the high resolution delta-sigma modulator is fully differential one. In that case the 2nd harmonic distortion is cancelled and with the feedback loop the 3rd harmonic is attenuated.
Now if we consider the normal audio channel (the transducer is often single-ended), so if I use a single-ended continuous-time delta-sigma ADC, do I have the problem of the SNDR due to the 2nd harmonic distortion? For example, if I want to achieve 16 bit resolution, is it possible? Would anybody recommend me some references?
Thank you.

Title: Re: How to achieve a high SNDR single-ended delta-sigma modulator?
Post by Jacki on Jun 28^th, 2018, 12:41am

First, even for the single-ended input signal, due to the feedback loop, 2nd harmonic can be suppressed. Further if we choose the CIFF, and only let the integrator processes the error (not the signal), the output swing will be much lower, and the distortion will be much small. Is this the reason we can achieve high-resolution delta-sigma ADC with the single-ended input signal?
Do we need to the single-ended to differential conversion at the first stage or some internal stage?

Title: Re: How to achieve a high SNDR single-ended delta-sigma modulator?
Post by Jacki on Jun 28^th, 2018, 9:50am

I read some papers and data sheet, I think if we only use single-ended delta-sigma ADC, harmonic distortion is a problem, so to achieve a high resolution / DR, we need the single-ended to differential converter as the first stage, then use the pseudo-differential to get the high-SNDR delta-sigma ADC. Please correct me if I am wrong, also welcome to list some high-performance single-ended to differential converter.
Thank you.