• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Subscribers 98 subscribers
  • Views 497 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Original question:

TDA4VM: TDA4 OSPI FLASH Device

TDA4VM: TDA4 OSPI FLASH Device DQS pull down resistance

Kuo Guo
Prodigy 130 points
Part Number: TDA4VM

Hi TI Team:

We have some problem about TDA4 design file.

We find the S28HS512TGABHM010 ospi flash have pull down resistance on the DQS pin in PROC105E6(001) design file.

But the MT35XU512ABA1G12-0AUT ospi flash does't have pull down resistance on the DQS pin in PROC078E8(001) design file.

What is the role of pull down resistance on the DQS pin?

If we use the MT35XU512ABA1G12-0AUT or other ospi flash,Is it must be have pull down resistance on the DQS pin?

Thanks！

  • 0
    TI__Expert 4015 points

    The pulldown resistor was added for compatibility with the S28H flash device.  It is not needed for MT35X.

    -Zack

  • 0 in reply to z
    Prodigy 130 points

    Hi:

    Thank you very much for your answer.

    I would like to ask you some other advice.

    Why is the S28Hx flash device need pulldown resistor on the DQS pin ？

    We can't find some requirements about it in S28Hx flash datasheet.

    Is it because pre drive in S28Hx flash device?

    Thanks！

  • +1 in reply to Kuo Guo
    TI__Expert 4015 points

    This is from the TRM:

    12.3.2.4.2.2 External Pull Down on DQS Per the OSPI protocol, the FLASH device drives DQS while CS is asserted. When CS is not asserted the FLASH device presents HiZ on DQS. When configured to use DQS, the controller uses the DQS as a clock, which samples the incoming data into a FIFO. Noise on the DQS when it is HiZ can cause spurious false triggering of the FIFO and filling it with invalid data. There is no way to clear this data except to reset the OSPI module. To avoid this issue, it is recommended to add a pull down on the DQS line.

    My previous statement, "It is not needed for MT35X", was slightly inaccurate.  We still recommend it.  On MT35X, the DQS goes to HiZ at a time that doesn't cause this issue, hence why it isn't present on these EVMs.  But it also wouldn't hurt to have the pulldown resistor.  For this reason, we recommend pulldown on DQS for all flash devices.

    -Zack