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TXB0106: TXB0106 and SD cards compatibility issue

Benjamin von Niederhaeusern
Prodigy 130 points
Part Number: TXB0106
Other Parts Discussed in Thread: TXS0206

Hi All,

We are facing sd card compatibility issues with the TXB0106.

Here is the initial interface configuration. The task is to boot from any SDcards. For the initial configuration (hope u can see picture that I tried to insert, 51K pullUps to 3.3V on the interface to the sd card) only the following card from our current sd card stock is working:  Kingston 64GB micro sdxc I U3

The following sd card do not work with this electrical configuration:

- SanDisk Extreme 32GB micro sdhc I V30 U3
- Kingston 16GB micro sdhc I U1 industrial

- Samsung 32 EVO Plus micro sdhc I U1
- Samsung 32 PRO Plus micro sdhc I U3

After changing values for the pullUps, checking the signals and the supply voltages we end up with the following el. config where all the cards work but the Samsung cards:

So the PullUps are at 1.8V and 100K now on the 3.3V side. As mentioned the following card do work now:

 - Kingston 64GB micro sdxc I U3

- SanDisk Extreme 32GB micro sdhc I V30 U3
- Kingston 16GB micro sdhc I U1 industrial

The follwing Samsung cards still don't work:

- Samsung 32 EVO Plus micro sdhc I U1
- Samsung 32 PRO Plus micro sdhc I U3

It's quite hard to find datasheets or any spec about the exact IO configurations of the SD cards. It looks like the Samsung cards do have a stronger Pull-Up on the cmd line for the initialization period and therefore "overwriting" the TXB0106 thus never receiving the cmd issued by the host (the Intel A10AS057 in our case). But this is just a guess... Any idea would be very appreciated!

Thanks in advance.

  • 0
    TI__Guru* 96591 points
    Hello,
    Your images didn't come through (what you see after posting is the same thing that I can see).

    I would highly recommend against using pull-up or pull-down resistors together with the TXB family of translators.
  • 0 in reply to Emrys Maier
    Prodigy 130 points

    Hi Emrys,

    Thanks for your reply and yes after sending my post I saw that the pictures were not added. So above is my next trial to add the pictures...

    The PullUps were added for the SDcard not for the TXB0106 and their values were chosen according to the recommendations of the TXB0106 datasheet (>50K) . In the meanwhile, we think to understand that even for the SDcard a pullUp on the CMD line only would be sufficient. The data lines seem to be push-pull from the beginning and the cmd lines changes from open-drain in the initialization period of the Sdcard to push-pull after it  changes to SD mode.

    Any further input or correction/support of the above is very welcome.

    THX

  • 0 in reply to Benjamin von Niederhaeusern
    TI__Guru* 96591 points
    If the TXB0106 is always active, then the lines should be at a valid state and the pull-ups would not be required. If you're disabling the TXB0106, then I understand the requirement for external pull-ups. Since the TXB0106 has very low drive strength, any external pull-up will cause some degredation of performance.
  • 0 in reply to Emrys Maier
    Prodigy 130 points

    Thanks Emrys,

    The TXB0106 is not disabled in our application. Are you suggesting to remove the 100K pullUps as they are not required by the TXB0106 nor by the SDcard? The signal on the CMD line look the following when a Samsung SD card is inserted:

    The signal level on both sides look correct when one of the other card types (mentioned above) is inserted.

    I'm aware that other devices like the TXS0108, TXS0206 or a LSF type may be the fast fix here and having all the cards working. But it would be nice to understand what exactly happens  and why some cards do work and the Samsung cards don't work in this particular setup. What is / what could be the difference here?

  • 0 in reply to Benjamin von Niederhaeusern
    TI__Guru* 96591 points
    I'm afraid that I can't speak for SD card manufacturers - I don't really know anything about how they design/build their cards, and I don't know the differences between a Samsung and a SanDisk/Kingston device.

    It looks to me like the 3.3V side signal shown is being very slowly pulled up to an invalid voltage by the 100kohm resistor, then driven high, then driven low.

    The other side appears to be getting dragged down by something. Can you show the input and output of the TXB on the same scope shot so I can see how they align? My guess from above is excessive capacitive load, but I can't be 100% sure.
  • 0 in reply to Emrys Maier
    Prodigy 130 points
    Thanks Emrys,

    We manged to get the design working by replacing the TXB0106 with a "almost" pincompatible TXS0108. All mentioned SDcard do work with the TXS0108. However, it requires some minor changes in the layout (as it is a 8 channel levelshifter; a TXS0106 is not available).
    The issue with the TXB0106 is still not understood. So if anybody has a clue I'm still interested.

    Thx
  • 0 in reply to Benjamin von Niederhaeusern
    TI__Guru* 96591 points
    Hi Benjamin,
    I requested some information from you -- if you aren't willing to work with me, I don't know how you expect to resolve the original issue.

    It sounds to me from your response that you have found a satisfactory solution and there's no need to try to determine what you had done wrong in your original circuit.

    If you have trouble with another company's parts (ie the SD Cards you listed), then I would recommend contacting them to find out why their parts don't conform to the same standard as their competitors. That's not something that I can resolve for you.

    As for the TI parts, I don't see that any of them are doing anything incorrect, and I have explained why already.
  • 0 in reply to Emrys Maier
    Prodigy 130 points
    Hi Emrys,

    Thanks for your helpful advices and please receive my apologies if anything I wrote hurt your feelings.

    Yes indeed, as the TXS0108 comes in a similar package as the TXB0106 I decided to go ahead with the TXS0108. However, from an engineering point of view it is not satisfying that the issue with the TXB0106 TOGEHTER with e.g. the Samsung Cards isn't solved/understood (that's also the reason why I couldn't click on 'resolved').

    I may come back to this issue providing more graphs and I may try to ask SAMSUNG for some support, but for now, we must go for the workaround to be able to follow the timeline.

    Probably other TXB0106 users (or potential users) are interested in this issue as well. Any further input / idea is very welcome.

    Thx
  • 0 in reply to Benjamin von Niederhaeusern
    TI__Guru* 96591 points
    Hey Benjamin,
    No hurt feelings. It's my job to resolve issues on here -- unfortunately in some cases the resolution is "TI can't resolve this issue" - so the whole "this issue is resolved" thing doesn't make a lot of sense.

    I hope you get help from Samsung!