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TPA3123D2EVM high Iq and non-op at high temps (>40C)

Emrys Maier
Guru* 96681 points
Other Parts Discussed in Thread: TPA3123D2EVM, TPA3123D2, TPA3130D2, TPA3118D2

Hello,

I am working with the TPA3123D2EVM.  When looking at its performance over temperature I found that in a temperature chamber set to +40C the TPA3123D2EVM will not power up properly or output any audio.  The chip on the board gets really hot in this scenario without any audio input/output (just quiescent current).

When the board does power up and is operational, the Iq I see is around 35-50mA.  When the device fails to power up properly, the Iq of the board is between 100mA and 150mA and the IC gets very hot to the touch.  In this state, injecting an audio input signal will not produce any audio output.

Are there any known issues with this audio amp IC/eval board or could I have gotten a defective eval board?

  • 0
    TI__Genius 9175 points

    Hello,

    The TPA3123D2 can get into a startup issue causing the exact symptoms you describe if the SD is not asserted correctly. This is caused by the method used to control pop and noise on startup.

    Please see the app note attached:

    /cfs-file/__key/communityserver-discussions-components-files/6/Hold-time-on-SDZ-TPA312xD2.pdf

    The TPA3123D2 is an older device. I would recommend reviewing our TPA3118D2 or TPA3130D2 for a modern stereo Class-D amplifier with similar power ratings.

    Best Regards,

    Matt

  • 0 in reply to Matthew Beardsworth
    Prodigy 30 points
    Thanks for the quick response.

    When the board was in its non-op state, I did try pushing the shutdown button on the eval board for about a second and letting go, but the amplifier still did not start up properly after releasing the shutdown button. Based on the app note, it sounds like using the shutdown button with sufficient duration should resolve the issue, but it didn't for me. Would you expect this behavior?

    I will try holding the shutdown button when applying power to the board and then releasing it a second later to see if that allows the board to startup properly.

    I would prefer to avoid changing amplifiers at the moment if I can get the one we have working properly

    Thanks,
    Rob
  • 0 in reply to Robert Klug
    TI__Genius 9175 points

    Hi Rob,

    Yes, using shutdown for a duration of time will clear any issues caused due to the startup sequence. However, excessive noise on the SD or Bypass may case the issue to creep back up due to an accidental trigger of the SD system.
     
    I currently do not have an EVM on hand of this board. Please allow a couple of days to get one in.

    In the meantime so I can better understand the issue can you clarify the setup? (Power supply voltage, loading, input signal level)
    What specific temperature that you are seeing the issue occur?
    Does the device exhibit this behavior if you slowly increase temperature while playing vs starting up at the high temprature?
    Have you looked for shorts on the board?

    Also can you provide the following scope shots:

    -Switching waveform when amp is in non-operational (Is the PWM still active?)
    -Output voltage and current (are you close to OC threshold?)
    -SD pin (any glitches on this pin?)
    -BYP to GND when device is in non-operational and operation state (does BYP stay up? is there a lot of noise on this pin?)

    Best Regards,
    Matt

  • 0 in reply to Matthew Beardsworth
    Prodigy 30 points

    I didn't realize until just now that J11 was installed on our board, enabling the external de-pop circuit on the eval board. Removing J11 seems to have resolved the issue, but we will be testing it more on Monday to confirm.

    If our tests fail on Monday, I'll try to capture the scope plots you've requested.

    Here's some info to clarify our setup (prior to removing J11):

    The board is being powered by a bench power supply. We've tried it at 12V, 16V, 20V, and 28V supply voltages with no change in behavior between the different voltages. We are planning on using it at 28V for our final application. We did notice during our tests with the supply set to 16V, if we slowly lowered the supply voltage by several volts when the board was in it's non-op state, the supply current would all of a sudden drop down closer to normal and the board would start functioning.

    Our load is two 8 ohm speakers. We're using the amplifier with a stereo output. We typically have no input signal when we power on the board (cables disconnected). We're using a function generator to provide a signal when it is connected. Signal drive voltage has typically been set to +/-0.2V. Gain jumpers were left at their default settings.

    I think the issue is mainly just at power up, but I haven't tested the scenario with warming up the board after it has been powered on.

  • 0 in reply to Robert Klug
    Prodigy 30 points

    Removing J11, disabling the additional power down de=pop circuit, resolved our no-op issue at warm temperatures. Thanks for your help.

  • 0 in reply to Robert Klug
    TI__Genius 9175 points
    Thank you for your feedback and closing the loop on this!

    Best Regards,
    Matt