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TPA2011D1: TINA simulation results unexpected

Simon Boyd
Prodigy 10 points
Part Number: TPA2011D1

Tool/software:

Using the provided TPA2011D1 reference design file ('SLAM049'), the results of an AC analysis are unexpected.

For example, running an AC analysis, the amplitude of the output is around -200dB, whereas I would expect this to be around +12dB given the design/gain resistors.

Am I missing something? Is the simulate model accurate? If it is, could somebody please explain the steps/parameters to run the AC analysis?

Specifically the model would be useful in my application, as we are planning to have some signal filtering of the input signal to the amp. Being able to reliably simulate that will save a lot of development time.

Thanks 

  • 0
    TI__Guru** 109055 points

    Hi Simon,

    Is the time domain simulation working correctly for you?

    Are you running the simulation without changes after downloading SLAM049? I'll try to replicate on my end.

    Best regards,
    -Ivan Salazar
    Applications Engineer

  • 0 in reply to Ivan Salazar
    Prodigy 10 points

    Hi Ivan,

    Yes using the unmodified SLAM049 file.

    Time domain simulation seems to be ok, so I guess I can use that as a workaround.

    Did you get a chance to replicate the AC analysis issue?

    In my application, we are actually use a 2-stage amplification, so feeding the TPA2011 with the output of another small class D amp. I expect it will be best to add a low pass filter before the TPA2011. I will run some simulations around this, but do you also have any recommendations for how best to add this, without impacting the gain/functionality of the TPA2011?

    Thanks,
    Simon

  • 0 in reply to Simon Boyd
    TI__Guru** 109055 points

    Hi Simon,

    Can you explain why you need to use the output of a Class-D amp to drive another Class-D amp? Do you need higher gain? This implementation will need a low-pass filter to prevent the PWM signal to reach the analog input of the TPA2011D1 amp.

    Best regards,
    -Ivan Salazar
    Applications Engineer

  • 0 in reply to Ivan Salazar
    Prodigy 10 points

    The first class D amp is integrated into a DSP chip we plan to use, which is not an easy chip to substitute out. The only output available to use from that chip is its class D output (i.e. we are unable to access the pre-class D signal).

    Unfortunately that integrated class D amp isn't suitable for us due to a few reasons - relatively high output impedance, not enough gain, not enough output power. So we plan to use the the TPA2011 as a second-stage amp to get around that.

    But yes, we need to solve that low-pass filter design to make sure we don't have issues with the PWM signal.

  • 0 in reply to Simon Boyd
    TI__Guru** 109055 points

    Hi Simon,

    Understood. In this situation I think you first have to add the filter to your DSP/CODEC and make sure an analog signal is seen at the output. Then TPA2011D1 can be added to the system.

    Best regards,
    -Ivan Salazar
    Applications Engineer