Non-linearity of sigma-delta ADC

[kuohsi]

non linearity sigma delta

I have designed a sigma-delta ADC (OSR=2048, BW=50Hz, fs=200kHz)
by switched-capacitor.
I run FFT in Hspice, and get the very poor linearity behavior,
Can anyone suggest for me?
thank you!

 

[wave3x]

sigma-delta+non-linearity

You should better descript your question in details , If you want the right answer.

 

[doraemon]

sigma delta adc linearity

Hello!

Wave3x is right, it would be better with some more detail. You don't tell us
what thee input of your filter is. Apparently it is a 6Hz (approximately) signal
but if your filter has a pass band of 50, I don't understand what is wrong.
Beside this, the stop band seems to be less than -80dB from 50 Hz which
is pretty good. But of course it depends on what you're looking for.

So if you want some more accurate replies:
- what is the input set of your FFT? Could you draw at least a block diagram
to explain what you do?

Dora.

I have designed a sigma-delta ADC (OSR=2048, BW=50Hz, fs=200kHz)
by switched-capacitor.
I run FFT in Hspice, and get the very poor linearity behavior,
Can anyone suggest for me?
thank you!