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TPS65950's PMU_STAT/LEDB control by BootROM

Jaya Kumar
Expert 1190 points
Other Parts Discussed in Thread: TPS65950, DM3730

Hi,

We're using a DM3730 based design similar to beagle-xm. We're having a small percentage of units fail in production. In this case, the mode of failure is that the unit fails to boot, and the D12 LED (PMU_STAT / LEDB) which is driven by the TPS65950 fails to get asserted. This does not involve any system software as the NAND flash and microsd interfaces are empty. The boards that fail in this way do not have the LEDB signal asserted. The good boards (also empty flash, microsd) get LEDB asserted. My understanding is that this signal is driven by BootROM. I have not been able to find out what would be the cause of failure / error detected by BootROM that would cause it to fail to assert LEDB. Am a bit stumped and looking for any ideas/suggestions. I've checked the sys_boot strappings and the failing boards have the same values as the good boards.

Thanks,

jayakumar

  • 0
    TI__Intellectual 1915 points

    Hi, LEDB is off by default at PMU level and it is turned on by SW by writing LEDBON bit to 1 in LEDEN register (0x00EE). So some SW must be running on good boards to do so. I would suggest monitoring I2C bus to see if any transaction to PMU.

    Best regards, Alain.

  • 0 in reply to AlainC
    Expert 1190 points

    Hi AlainC,

    Thanks for your reply. If by SW, you mean the TI BootROM (this is the ROM code that lives in the DM3730 and is not typically customer changeable), then you would be correct. If instead you meant, firmware (like x-loader, u-boot, etc) that is loaded by bootROM from microSD or NAND flash or etc (as per sys_boot strappings), then this is not the case because the good boards have no software loaded (empty nand flash, no peripherals, no microsd, no usb), the same as the bad board. So what I'm trying to determine is what would cause the TI BootROM to not set LEDBON. 

    Thanks,

    jaya

  • 0 in reply to Jaya Kumar
    TI__Intellectual 1915 points

    Hi, all I can tell is that at some level this bit must be set for the LED to turn on hence my suggestion to trace I2C transactions to see when it is happening.

    Best regards, Alain.