• State Resolved
  • Locked Locked
  • Replies 2 replies
  • Subscribers 97 subscribers
  • Views 303 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.

OMAP3503 VDDS_MMC1 power up sequence issue

Vini
Intellectual 895 points
Other Parts Discussed in Thread: OMAP3503, TPS650731

Hi All,

We are facing a very strange issue on my OMAP3503 based issue.

We are using OMAP3503 CBC package and TPS650731 PMIC. And LDO2 of this chip is used to supply the power to OMAP VDDS_MMC1 domain. Only 4-bit SD interface is used. So, VDDS_MMC1A pin is connected to GND thorugh 10K as per OMAP schematic checklist.

LDO2 in TPS650731 is disabled by default and is enabled using I2C in bootloader. This is much later than reset release from OMAP but as we do not need SD/MMC boot and thats why LDO2 was used for SD/MMC power. As per my understanding, it should work without any issue since OMAP power ON sequence says VDDS_MMC1 can be supplied after reset.

Now, coming to actual issue we are not able to make SD work with this configuration. We tried to toggle SD lines as GPIOs and all the lines except SD_CLK are toggling. SD_CLK always stays LOW. While debugging, we gave external supply to VDDS_MMC1 that is enabled by OMAP GPIO at power ON (before reset is released) and to our surprise SD card was detected and we were able to do read/write from it. We again tried with LDO2 and again same result.

Now, the question is why OMAP should behave like this? Is there anything that we are missing here?

Vini

  • 0
    Intellectual 895 points
    Hi All,
    This issue got resolved by setting the PBIASLITEPWRDNZ0 bit of CONTROL_PBIAS_LITE register of OMAP. We are able to work with power from PMIC itself.
     
    But may be TI still has a good point to investigate furhther that why it was working with external 3.3V (released before reset) without even setting this bit.
    Can anyone clarify?
    Vini
  • 0
    Intellectual 895 points

    One more point that I forgot to update in previous post.

    Initially I said that all the SD lines except SD_CLK are toggling as GPIOs. I think that was due to the pull up on all other lines (SD data and cmd lines) and I am not usimg any pull up on SD_CLK line as recommended by OMAP schematic checklist. After pulling up the SD_CLK line with 10K externally, I was able to toggle this line also as GPIO but the communication on SD was still failing.

    Vini