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Ryan Curran

Undersampling: Applications & Techniques With SAR ADCs, Part 2

Ryan Curran
Arv747
Arv747
6/30/2016 6:43:03 AM
User Rank
Newbie
AD7091R-8
Hi All,

I am using AD7091R-8 for sine wave analog data aquisation having 48V(p-p), but getting issues like one sine wave which is connected to ch_0 affecting other channel input reading.If anyone have some solution please let me know.

 

Regards,

Arvind.

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ryancurran
ryancurran
12/15/2014 11:07:00 AM
User Rank
Blogger
Re: Informative - AD Product
The current draw of a SAR ADC largely depends on the sample rate of the device, not whether this sample rate upholds the nyquist criterion. For example, if the ADC is sampling at 100 ksps, the current draw will be the same if the signal of interest is 20 kHz or 200 kHz.

I envision undersampling techniques most valuable in multichannel sequentially sampling systems.  Here the ADC core may be sampling at a sample rate that does not violate the nyquist criterion. However, only every n-th sample will be associated with a given channel, effectively reducing the nyquist frequency of a single channel relative to the output data rate. The analog bandwidth of the system is able to handle the signals of interest, but the sampling techniques may result in an aliasing effect that must be accounted for.

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DaeJ
DaeJ
12/14/2014 3:10:06 PM
User Rank
Master
Informative - AD Product
->Figure 1, the average current draw of the device scales linearly with the sample rate because most of the current draw occurs during the active conversion period. If the conversion process happens less often, then less current is consumed.

There are two aspects that I would like to point: Firstly, If there is the comparison of current drawn from other product in between undersampling and regular sampling, customer might see performance comparison among other product. Secondly, is there any application note that undersampling has a huge benefit?

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More Blogs from Ryan Curran
Traditionally, undersampling is utilized in communication applications where a range of non-baseband signals sitting above the nyquist frequency are desired to be sampled. The bandwidth of these signals is less than the nyquist rate of the sampling system.
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