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Kinetis K70 ADC noise performances issue

Question asked by Cesare Masetti on Jun 24, 2014

Hello everybody,

I'm writing to know if somebody has found some noise issues while using K70 ADC module.

I have a TWR-K70 120 MHz module, TWR-LCD-RGB module and TWR-SER module assembled together (with primary elevator too, of course). I have been working with Kinetis K60 100 MHz for almost two years, both with TWR-K60 module and some custom boards.

I have recently ported one old K60 project to K70 on the tower module and everything seemed to work fine. However, I noticed that the ADC results are much more noisy compared to the ones obtained not only on my custom boards but also on TWR-K60. I have tried to remove the other modules and load the ADC demo with the same results: the samples on K70 are 30% to 40% much noisier than the ones retrieved with K60. Different configurations (different analog ports, lower clock speed, longer sample time and 4 samples average, tried both external and internal reference) yeld more or less the same results.

Has anybody experienced something similar? Does anybody know if this is a TWR-K70 issue, due to not-so-good layout maybe, or an intrinsic behaviour of the K70 ADC module mask? The module should be identical to the K60 one looking at the datasheets.

Hope somebody can help me since this noise problem would be critical to my application.

 

Thanks in advance,

 

Cesare

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