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DLPA2005: RESETZ behaviour after DMD_EN

Yai Sagolsem
Prodigy 60 points
Part Number: DLPA2005

Tool/software:

My system is pulling RESETZ low briefly after DMD_EN is set causing the system to reset (as the DLPC is reset).  If this is the case, is UVLO the only possible fault that would cause RESETZ to be pulled low like this?  This is what I am gathering from the datasheet.

Thanks,

Yai.

  • 0
    TI__Genius 11555 points

    Hello User,

    If you see PROJ_ON stay ON when RESETZ is pulled low, then I suspect that INT_Z also pulled low, can you please confirm?

    This could be caused by UVLO interrupt, but this may not the only fault pulled RESETZ/INT_Z to be low. Table 23 from the DLPA2005 datasheet describes other faults. 

    Regards,

    Lori 

  • 0 in reply to Lori Wang
    Prodigy 60 points



    My system nominally runs at 3.3V but after raising the voltage to the DLPA2005 to 5V, I am able to boot the diagnostics firmware without the system resetting.

    EDIT:  The inductor issue was a result of incorrect bulk capacitors on VLED, this part of the issue is now resolved, however, I still cannot boot the system on 3.3V due to the inrush current being too high still.

    However, there is another issue that presents itself that makes me wonder if my DLPA2005 may be damaged.  As my application has zero use for the VLED driver, I was intending to leave the PMIC running in Active 1 state or Active 2 state driving low power 3mm LEDs as a dummy, (the information as to whether the PMIC could operate without LEDs on the forums was inconclusive) and as such I had designed the board using the same 0805 2.2uF inductors that are used for my 3.3v, 1.1v and 1.8v supplies.

    When the system starts booting, this 0805 inductor (which is not powering anything as I had disconnected the LEDs), started heating up hot enough to vaporise some leftover flux on the board.  I checked for a short of the VLED output but could not find any reason for the inductor to be outputting enough current to cause such high temperatures.

    I am wondering if the low side mosfet may have been damaged somehow or if I am simply misremembering how these switching supplies should behave, as if this is the case it may explain why UVLO was tripping since there is current being drawn somewhere to require enough power to cause a Vdroop and overheat the inductor.

  • 0 in reply to Lori Wang
    Prodigy 60 points

    Would it be possible to get a customised firmware which sets the LED output to be off by default or be at the lowest current setting? 

  • 0 in reply to Yai Sagolsem
    TI__Genius 11555 points

    Hello Yai,

    It's hard for us to decided if there is any damaged happened on your custom design board, but noticing the board/components getting hot is not a good phenomenon. There could be a high possibility that the part got damaged.

    You should be able to leave the LEDs unconnected. What's the controller you are using to pair with the DLPA2005 board?

    Regards,

    Lori