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Problem with gain inputs

Carlos Vargas

Other Parts Discussed in Thread: TPA3123D2

Hello! I'm mounting a prototype according to the evaluation module for TPA3123D2 and there are some issues. Once the prototype was finished it begun to oscilate with a small pulse about 3.8Hz, without sound. To remove this, I simply disconnect the 1 uF capacitor (C6 to pin 11 VCLAMP) and it started to work properly. Can this pin still unconnected or what kind of capacitor do I need?

That's  the minor problem, the mayor problem is when I try to set any of the gain inputs to VCC the amplifier starts to oscilate, blocking the sound. Only works well when that inputs are tied to GND. In addition to this, the normal consumption is about 50mA
but when the jumpers are open (so +12VCC pull up) the consumption rises to 500mA causing undesirable heating of the chip.

The output configuration is single ended.

Any suggestions?

Thanks in advance.

Carlos Vargas

  • 0
    TI__Guru**** 189401 points

    Hi, Carlos,

    Operation without a cap on VCLAMP is not recommended. You should always use the same components that we have used on the EVM. In this case, the VCLAMP cap is a ceramic, 1.0 μF, ±10%, X7R, 16V.

    I suspect a problem with your output filter or layout. What components are you using for the LC output filter?

    -d2

  • 0 in reply to Don Dapkus
    TI__Guru**** 189401 points

    Sorry, Carlos,

    I got so excited I forgot to ask you to post an oscilloscope shot of the 3.8 Hz to see what the outputs are doing pre-filter, please.

    -d2

  • 0 in reply to Don Dapkus
    TI__Guru**** 189401 points

    Hi, Carlos,

    I am just following up to see if you got this sorted out, I never heard back from you.

    -d2

  • 0 in reply to Don Dapkus

    Hi Don, sorry, I really apologize for my delay. Effectively, things changed when I replaced the type of capacitors according to your suggestions. More than the VCLAMP capacitor, the bypass capacitor on pin 7 was the actual responsable of the malfunction. The performance improved a lot, including the undesirable oscilation, although the problem persist when the input gain 0 is off; gain 1 works well.

    About the layer... Oh yes, I admit is not the best one, actually is a general purpose board, so I´m sure when following the directions to emulate the EVM it will work as we expect.

    In fact, there's 30 units to produce and sell at the beginning of March. I hope to keep you updated about the evolution of this project.

    Thanks a lot for your support.
    Sincerly,

    Carlos.

  • 0 in reply to Carlos Vargas
    TI__Guru**** 189401 points

    Carlos,

    Excellent! Sounds like you are making good forward progress!

    -d2