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May 20th, 2019, 3:21am
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SNDR calculation in a delta sigma DAC (Read 429 times)
polyam
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SNDR calculation in a delta sigma DAC
Dec 19th, 2018, 8:59pm
 
Hi,

I've designed a delta-sigma DAC. My reconstruction filter has a pass-band frequency of 10 MHz and a stop-band frequency of 100MHz. My delta-sigma is clocked at 800 MHz for an OSR of 128. So the BW is about 3MHz. Now the question is that in which bandwidth I should calculate the SNDR? 3MHz of fs/2=400MHz. If I calculate it over 3MHz I'll have SNDR=101 dB. If I calculate it over 400 MHz it will be 38 dB. Which one is correct?

tnx
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polyam
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Re: SNDR calculation in a delta sigma DAC
Reply #1 - Dec 19th, 2018, 9:00pm
 
I added the output spectrum after the reconstruction filter.
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jdp
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Re: SNDR calculation in a delta sigma DAC
Reply #2 - Jan 13th, 2019, 4:51am
 
Integrate the noise till the half the Nyquist rate of the desired input signal freq band. If the desired signal can lie in dc to say 4MHz, then you should integrate till Nyquist rate/2=4MHz.
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