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SD card mounted causes a lot of interference, perturbing the ADC

Question asked by prieur.jean on Jun 18, 2015
Latest reply on Jun 19, 2015 by prieur.jean
Hello everybody,

I use a SD card (SDIO).

- When the SD card is inserted but not mounted, my analog inputs convert voltages with a very good precision.
- When I mount the SD card, my analog inputs starts to convert voltages with a very poor precision.
- When I unmount the SD card, same problem. 
- When I unplug the SD card, my analog inputs convert voltages with a very good precision.
- When I re-plug the SD card, same problem of precision.

I think it's because the SD card plugged and mounted causes a lot of interference? I tried to analyze the electromagnetic field near the SD card and it's true, when the SD is mounted there is a lot more interference.

The fact is, in my board design, the analog inputs tracks are routed near the SD card. There is a high probability that the analog inputs capture the noise of the SD, do you ever experienced this problem?

Do you think there is any workaround? I can't change my electronic design... For example, can I fully deactivate the SD after the unmount? Because the unmount is not enough and there is still interference.

Thanks a lot for your help, I hope there is solution!

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