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Noise Spike in ADS 1299

Other Parts Discussed in Thread: ADS1299

Hi,Everyone

I am doing a project , using beaglebone black acquire the front end data from SPI interface . I have tested with internal stimulus (square wave provide by ADS 1299 itself)   and external stimulus (sin wave provided by function generator) .The results is that I always get the spikes which are much bigger than the stimulus .I set the mode of ADS199 is Read Data Continuous Mode .Sequence of commands in your read cycle is that WAKEUP ,START,RDATAC,STOP,SDATAC,STANBY and also i use poll function to check the data ready signal during each transmission.

Besides when i choose the different SPI clock rate(I choose 1600000,800000,80000 HZ) ,the results are different . The higher the clock rate seems to have better result . But still can not completely avoid these strange big spike .

Has anyone has any ideas?

Thank you very much

Summer 

  • Hi Summer,

    Thanks for your interest in ADS1299!

    This sounds very similar to another question posted earlier last month. Does this issue coincide with what you are also observing? http://e2e.ti.com/support/data_converters/precision_data_converters/f/73/t/363987.aspx

    My colleague suggested in his reply that this may be related to a clock timing issue. As you mentioned, higher clock rates seem to have better results. Try triggering your data logger on the "spikes" and look at your SPI signals at that moment. You may need to adjust your timings, please confirm that they meet the specifications in the datasheet.

    Regards,

  • Hi 

    Thank you very much for your reply . I will have the chance to test the day after tomorrow . Before that , I still have a question . Yesterday I found that when a power down the input (that is ,the input is all zeros ) I still see several big spikes in the results. I was wondered do you have any advice or idea on this?

    Thanks.

    Best regards,

    Summer