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TAS5630B: Amplifier Overheats in noload condition TAS5630B

ardhendu das
Prodigy 100 points
Part Number: TAS5630B
Other Parts Discussed in Thread: TAS5613, TAS5630

Hi,

We have designed a range of amplifiers using the TAS5630B,TAS5613 and TPA3118 , during production we found that some amplifiers that use the TAS5630B chip overheats even without any signal & load being present , we went further ahead and removed the output inductors to see if its dumping energy on the output filter , but even with the inductors disconnected the chip heats up and goes into protection... this is the wave form we are seeing on output of the chip with the inductor disconnected , there seems to some form of glitch,oscillation on the output ... What might have gone wrong ...???

regards

Ardhendu

  • 0
    TI__Mastermind 30090 points
    Hello Ardhendu,

    I'm sorry to hear that you are having some problems. I will do everything I can to help you figure this out. First I've sent you a private message so that I can get a schematic, layout, or picture of the PCB. This could help us in identifying the problem.
    In regards to the glitch, Do you see any corresponding activity on the SD pin?

    More information would be very helpful. What mode are you using? what is your PVDD? What is your load?

    best regards,
    -Steve
  • 0 in reply to Steve-Wilson
    Prodigy 100 points
    hi steve ,
    we are using the following ...

    1. BD mode
    2. PVDD - 48V
    3. LOAD - 4E & Output transformer

    And regarding the glitch on the SD pin we are trying to capture that .... its not that every unit fails , the failure is very random say one in a batch of 50 or so ...

    Regards
    Ardhendu
  • 0 in reply to ardhendu das
    Prodigy 100 points

    So we found out the problem why we were getting the over heating the bootstrapping capacitor had actually failed , although the part are 1206 X7R 33NF/100V .

    We have a couple of field failures where the amp has failed .. the situation is the amp is connected to the output transformer and the output transformer gives 70V & 100V outputs , on the 100V output a auto-transformer based speaker is connected. We were drawing only 7.5W out of TAS5630 in the above mentioned situation when the chip failed .We took some measurements of the auto transformer based speaker, (www.communitypro.com/sites/default/files/CS8_SPEC_1.pdf)

    .

    Can you check on your EVM boards and tell us whats going wrong .

    Regards

    Ardhendu

  • 0 in reply to ardhendu das
    TI__Mastermind 30090 points
    Ardhendu, yes, I can take a look at a similar system. We were just testing the new TPA32xx series with 70V and 100V systems, so we have a number of transformers here. I will take a look, discuss with our team and get back to you.

    -Steve
  • 0 in reply to Steve-Wilson
    Prodigy 105 points
    Just to conclude this thread.
    We found that the reason the amplifier was overheating was due to the excess current draw at idle.
    It was identified as the failure of bootstrap capacitors (33nF 100v ceramics)
    During heatsink assembly the PCB was being warped slightly which caused the ceramic capacitors to fracture and fail.
    Without the bootstrap capacitors the IC drew far more current dumping it into the heatsink and eventually entering thermal protection.

    Replacing the bootstrap capacitors fixed the issue and the amplifier worked correctly.

    The additional post above with respect to the auto-transformer is a new issue. I will post a new thread for this issue.
  • 0 in reply to euan brown
    TI__Mastermind 30090 points
    Euan,
    I am glad that you were able to identify the problem. The bootstrap capacitors are of course vital for proper function.

    We will do what we can to help with the auto transformer issue as well. I will await the new thread.

    best regards,
    -Steve Wilson