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AM3359 damaged

yi li2
Intellectual 615 points

Other Parts Discussed in Thread: TPS65910, AM3359

hi,

    we are using am3359 in our custom board. and our custom board contain 2 parts. one is the core board which contain main chips(am3359, tps65910, ddr2, nand flash, 100M phy), the other is the base board which contain other peripheral chips. when powered up, the core run first by DC-DC from the base board, then it switch on  the  power of base board chips.

     the board worked normally with AC adapter for about 6 months, but now 2 AM3359 damaged withbattery supply, we 've measured that VAUX2 3.3V short to ground, 

     What reason can causes this kind of damage?

  • 0
    TI__Guru**** 393215 points
    Hi,
     
    This is only guessing, since we don't have any information about your boards, but you should check if AM335X I/O pins get biased before all AM335X power supplies have ramped-up and stabilized. Take note that all AM335X power supplies must in the ideal case ramp-up simultaneously with power supplies for the peripherals that are connected to the AM335X. The AM335X I/O pins are not fail-safe, with the exception of USBx_VBUS pins.
  • 0 in reply to Biser Gatchev-XID
    Intellectual 615 points

    hi Biser Gatchev-XID,

        Thanks for your help, in our custom board, the power supplies for the peripherals are controled by AM3359 IO pins, and those power supplies are closed by default(by pull down resister).

        Now we  measuring and watch some voltage again, when AM3359 damaged, the step looks like this:

       1  we connected battery(16V) to our custom board, it connected to the power ic 65910 through DC-DC 5V

       2  AM3359 start up, it load SPL from NAND,

       3  the SPL SW opened the power supplies for the peripherals. at this time ,we catched that there are large voltage drop in the battery voltage, 

        4 in step 3, the power supplies for the peripherals should be opened, but we measured that it couldn't be opened, and the output of 65910  VAUX2 3.3V is 1V, then the temperature of 65910 and AM3359 rose,

        5 over a period of time, VAUX2 3.3V short to ground because of AM3359 damaged

  • 0 in reply to yi li2
    TI__Guru**** 393215 points
    Have you tried to enable the peripheral power supplies not from software, but from VAUX2? it seems to me that there is a current drain through AM335X I/O pins to peripherals that are not powered yet.