iMX8 micro-SD card EMI/RE(30MHz~1GHz) Failed at Write mode

[DaveMeng]

Hi NXP team,

We have an issue when pre-test EMI/RE 30MHz~1GHz when we write files into the SD card, our SD card clock frequency is ~200MHz. We also try to increase the terminal resistor value from 22R to 49.9R, also add a bypass capacitor 10pF at the iMX8 side(closed to the terminal resistor). We found a little improvement. And we refer to the reference design, the clock terminal resistor placed on SD card side(not iMX8 side). Would you help to share your suggestions to solve this issues.

Thanks

Dave

[weidong_sun]

Hi Dave,

Just suggestions to share with you.

Usually to solve EMC problems, you need to start with 2 aspects:

1. You can try to connect a magnetic bead in series with the clock line.
2. In the PCB layout, wrap the clock line with GND

Hope above ideas are helpful to you.

Have a good day!

Regards,

weidong

[DaveMeng]

Hi Weidong,

Thanks for your feedback. It looks like my responses missed from the page.

About your suggestions:

1. You can try to connect a magnetic bead in series with the clock line.

Dave--Which type magnetic bead would you like to suggest ?

2. In the PCB layout, wrap the clock line with GND

Dave-- Yes. The clock line wrapped with GND, also the clock line buried in the inner layer

Thank you

Dave Meng