Max.Track Length of 32GB UHS Class 10 MicroSD Card signals?

[sagar_kumar]

Hi

We are interfacing 32GB UHS Class 10 MicroSD Card with i.MX6Q. Please let me know the maximum trace length applicable for CLK, CMD and DATA lines in layout.

Also suggest us some technique to increase signal integrity if we violating track length limitation due to mechanical constraints.

Thanks

Sagar

[sagar_kumar]

Hi Igor

That points we already read from those documents but there is not clarity over trace length over there regarding SD Card Signals. Since we have mechanical constraint our trace-length is going more than 5 inch. Please let me know 5 inch trace length will not create any issue. We are following all the layout guidelines there.

If i follow this equation - Trace Length <= (0.3 x Rise/Fall Time x 15 cm/ns). rise time mention in datasheet for SD/eMMC4.3 Interface is 3ns then we are getting trace length is 5.31 inch. Is it correct to follow this equation in my case?

Thanks

Sagar

[igorpadykov]

Hi Sagar

it is not possible to say "5 inch trace length will not create

any issue" as this depends on specific board and its layout. So

you shold perform ibis modelling and check timings, comparing

them with datasheet usdhc timing requirements.

Best regards
igor

[igorpadykov]

Hi Sagar

implications caused by trace length are well described in

sect.5.3 Minimizing Reflections AN4215 Design Guidelines
https://www.nxp.com/docs/en/application-note/AN4215.pdf

Recommendations for sd layout are given in

sect.3.6.8High speed signal routing recommendations Hardware User Guide

https://www.nxp.com/webapp/Download?colCode=IMX6DQ6SDLHDG 

Best regards
igor
-----------------------------------------------------------------------------------------------------------------------
Note: If this post answers your question, please click the Correct Answer button. Thank you!
-----------------------------------------------------------------------------------------------------------------------