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TPA3126D2: Device switches to limited power if die temperature is too high

Jerry Peck
Prodigy 90 points
Part Number: TPA3126D2


Tool/software:

I narrowed this down to a thermal issue. The device switches to limited power automatically but there is no mention of this in the data sheet. Is this normal? There is no FAULTZ flag issued during the low power lockout. For instance, during continuous power drawing 3 amps, if the device temperature rises too high there is a FAULTZ flag that repeats because pins 2 and 3 are shorted.   However, after several fault and reset events, the device power reduces by about 1/2 or more. Also, the power limit pot has no effect when adjusted. I think this function is normal but had me really confused because it isn't addressed in the data sheet. My question is am I correct in this assumption?

Thanks,

Jerry

  • 0
    TI__Mastermind 20541 points

    hi Jerry

    it seems strange.

    after several repeats and reset, does this amp still can work normally? does it have any damage or not?

    thanks

    jesse

  • +1 in reply to Jesse Ji
    Prodigy 90 points

    Hi Jesse, it works normally after reset but only for a short time and no damage. I was using a heatsink with a adhesive thermal pad and I believe at high current peaks i.e. 5 amps the die heats up faster than heat can pass onto the heatsink. I made a single plate aluminum heat sink and used heatsink compound and the device stopped exhibiting this behavior. I set the signal generator to burst mode for 20% duty cycle during which the peak current was 5 amps. I did notice a gradual reduction in current consumption but I understand the chip will reduce gain slowly as temperature rises. This is OK. I am using the device for ultrasonic communications at 20kHz. It is for SSB voice communication and because the short duty cycle i.e. voice peaks of 5 amps will occur, this will not be a problem. My original question still remains and is a mystery as to why after several fault events the device seems to lock the gain to a very low value. I suppose this may be a final step in the chips design for self protection? Anyway, for my purposes it works like a charm as long as you use a heatsink with direct contact (using thermal compound) and not with a thermal adhesive pad. I believe the heat must be removed quickly and direct heatsink contact is the way to go just like the heatsink on the EVM.

    Thanks,

    Jerry

  • 0 in reply to Jerry Peck
    TI__Intellectual 2970 points

    Hi Jerry,

    Thanks for your detailed feedback.

    it seems you now have a alternative solution. if you still have more issues, let's check it again.

    Br,

    Wenbin