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TPA3100D2 and TPA3100D2EVM

Christopher Parris
Prodigy 10 points
Other Parts Discussed in Thread: TPA3100D2

I recently bought the TPA3100D2EVM to do some prototyping work and verification.  The eval board worked perfectly so I decided to integrate the TPA3100D2 chip into my PCB design.  I followed the schematic and PCB artwork from the eval board.  When I power up my board, the audio amp fault pin is always set to '1' (~4V).  According to datasheet, this means that one of the output pins is shorted to ground, VCC, or each other.  The weird thing is, that when I check for shorts with my meter, sometimes it indicates a short and other times it doesn't.  And it varies on the different output channels.  I have thoroughly investigated my PCB and schematic and there are no flaws in that regard.  Does anyone have any ideas as to what I am seeing with my fault pin and the occasional short to VCC?

If this helps, here is my schematic without all the jumpers and such from the EVM board.

  • 0
    TI__Intellectual 1050 points

    Hello Chris,

    I'm not certain why you are getting a fault, but you are right that it indicates an OC condition, due to a short at the output. How do your shorts vary by output, and is there any clue as to when it shows as short and when it doesn't? You said you have thoroughly checked your layout, which is good, which makes it odd that you get the "occasional short to VCC". 

     It does look like your schematic follows the EVM schematic. I do note on your outputs that you didn't put the RC snubbers for constraining EMI (For LOUT, R9/C25 + R10/C26 on the EVM), and that you have both a bridging cap and caps to ground. You may want to reference this app note regarding such a configuration, and double-check your values.

    Best regards,
    Arnold Zhang 

  • 0 in reply to Arnold Zhang
    TI__Intellectual 1050 points

    Hello Chris,

    I may have linked the app note above incorrectly. Here it is again.  

    Best regards,
    Arnold Zhang 

  • 0 in reply to Arnold Zhang
    TI__Guru**** 189399 points

    Hi, Christopher,

    Welcome to e2e, and thanks for your interest in our products.

    In addition to what Arnold said, I would look at your output inductors. I bet that they are saturating, and drawing huge peak currents. Remove the caps to ground after them, and I bet your issues will go away. Then, you just need to find inductors with better characteristics.

    Let us know how you're progressing.

    -d2

  • 0 in reply to Don Dapkus
    Prodigy 10 points

    Hello

       This is my first time using this forum - probably not the correct way to post my issue but what the heak.

    Here goes - I designed an audio amplifier based on the TPA3100D2 EVM kit.   I am using the TPA3100D2 chip and have release the design for close to a year now.   I am getting a bunch of field failure that I am starting to dig into at the moment.  I am finding the outputs has been shorted or at lease burning up speakers.   Some time one channel and sometime both.  These amps has worked in the field for while before going bad.  Has anyone else experience such failures?   Any debug idea would be helpful.  Note: The amp resides inside gas pumps.