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TXB0108 and SD/SDIO Controller

Rowan Carter
Prodigy 10 points

Other Parts Discussed in Thread: TXB0108, TXS0206

Hi

 

For the past few days I've been trying to debug a level shifting circuit that uses the TXB0108 that shifts 1.8V to 3.3V for use with an SD card.

I have put 100K pull ups on all lines ( DAT0:3,CMD) and no pull-ups on the CLK line. I've tried putting 67K and 50K pull-ups, neither work.

When i analyze the logic at the 3.3V the DAT Lines are not high, which they should be due to the pull ups however at the 1.8V side all signals are high ( except for the CLK obviously). From the logic analyzer it looks like the CLK and CMD signal are going through to the SD ok however the SD is not responding them.

Is there something that I am doing wrong? Why are the signals at the 3.3V not high?

I have made sure there is no Open Drain on the CMD line (disabled in software). And the CMD line looks like it is operating fine shifting from 1.8V to 3.3V.

Pull-ups in the processor are all disabled.

The following is my circuit:

 

Thank you.

  • 0
    TI__Genius 9085 points

    I'm sorry that the reply is so late on this. Hopefully you have resolved the problem!

     

    You're schematic looks correct to me. The TXB0108 should work find for SD applications. However, if you're using open drain drivers, like for MMC,  you may run into issues.

    It sounds like you are operating in push-pull, and not open drain, so I'm not sure why the signals on the 3.3V are not high. What voltage are they at? How heavy is the capacitive loading at the DS connector? Are there relative short traces? You're using the PW package?

  • 0 in reply to Hattie
    TI__Genius 9085 points

    Another option to look at is the TXS0206. 

  • 0 in reply to Hattie
    TI__Expert 4705 points
    Hi, Harish
    Usually, inside the SD card or Processor, there may be integrated some pull up or pull down resistors.
    Even you don’t have it in your schematic, they still exists.
    When you remove the SD card, is the translation correct?
    You should have CLK, CMD and four data lines, do all of them have the same issue?
    When you change the TXS0206, is the issue still here? How about the removing the SD card while using the TXS0206, is the translation correct?
    If still not, could you please provide the waveform to us for analysis?
    For easy replacement, you can use the TXS0108, you may find the p2p replacement part with TXB0108.
    BRJunjie