pull-up resistor of CMD line in SD card

[ko-hey]

Hi all

I have a question about pull-up resistor of CMD line.

Here is a comment about pull-up resistor of CMD line in P10 of SABRE-AI_DualLite_CPUcard/sch-27767_a_x3.pdf.

"SD, SDXC - Remove CMD pull-up resistor (default)"

Does it mean user can remove CMD pull-up resistor when use only SD,SDXC ?

Ko-hey

[Yuri · Accepted solution]

Hello,

  The pull-up on CMD is intended for eMMC, where it can be open-drain.

 
Have a great day,
Yuri

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[ko-hey]

Hi　Yuri Muhin

In my understanding, open-drain requires pull-up.

Since the internal pull-up of i.MX 6 can be used, it is not necessary to provide a pull-up resistor externally.

Am I correct ?

Ko-hey

[Yuri]

Hello,

  internal resistor values of i.MX6 are relatively big (~100K):

strictly speaking such values may be not sufficient. 

Regards,

Yuri.

[ko-hey]

Hi Yuri Muhin

Do you recommend an external pull-up registor ?

How big ?

Ko-hey

[Yuri]

Yes - external resistor about 4.7K

~Yuri.

[ko-hey]

Hi Yuri Muhin

According to your answer, it seems preferable to pull up the external CLK and D0 to D3 lines other than CMD at 4.7k.

Am I correct ?

Ko-hey

[Yuri]

Hello,

  Customers can just follow the reference design. 

Regards,

Yuri.