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TPA3005D2: Output burning 8-Ohm speakers

Casey Gross
Prodigy 20 points

Part Number: TPA3005D2
Other Parts Discussed in Thread: PCM2912

Hello, I am designing an amplifier using the TPA3005D2.

I received a few boards from the fab today and I noticed upon first power up that while an 8-ohm speaker is connected both the IC and speakers get very hot. eventually damaging the speaker. With the speaker left disconnected I have noticed the ROUTP & ROUTN pins have 9V across them when the device is powered from a 12V supply. Below is the schematic for the TPA3005D2 device by itself.

TPA3005D2pdf.pdf

  • 0
    TI__Guru** 114635 points

    Hi Casey,

    I'm redirecting your question to the proper support team. In the meantime, is this 9V you mentioned the PWM signal from the Class-D output?  Notice that this type of amplifier will be switching between PVDD (or any other name for the power supply) and GND.

    Best regards,
    -Ivan Salazar
    Applications Engineer

  • 0 in reply to Ivan Salazar
    Prodigy 20 points

    Hi Ivan, thank you for the response.

    Yes, 9V was the RMS voltage on the PWM output of the amplifier.

  • 0 in reply to Casey Gross
    TI__Guru 63380 points

    Hi Casey

       I didn't find the input capacitor in your schematic. Even you use single ended input, there still should be capacitor before you connect INN to GND.

       Can you provide the differential waveform at both the input side and the output side? We want to have a check. Thank you.

  • 0 in reply to Shadow He
    Prodigy 20 points

    Thank you for the response.

    Both LINP and RINP are connected to the PCM2912 audio codec on a separate sheet. They are connected together with a 0.47uF capacitor (Not Shown). I wont have access to a scope for a couple weeks as it is in Cal. Is there anything else I can check in the mean time. I used a simple POCKIT meter to look at the waveform on ROUTP to GND. This signal was essentially just a DC voltage with an offset of 9V, there wasnt an AC component.

    thank you,

    Casey

  • +1 in reply to Casey Gross
    TI__Guru 63380 points

    Hi Casey

        From the below picture the LINN is connected directly to GND, right? I think it will cause problems. We need to put 0.47uF capacitor at both of the input port, because our device will try to establish DC bias voltage at both of the input, so you can send in AC signals.

         If as you said, there's capacitor at the LINP side, so the DC bias can be set up at the LINP side, but LINN is 0. There would be DC voltage as the differential input. So you will also get differential DC output.