• State
  • Locked Locked
  • Replies 9 replies
  • Subscribers 30 subscribers
  • Views 255 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPA2011D1: TPA2011D1 output noise high and Waveform distortion

kai wang
Prodigy 10 points
Part Number: TPA2011D1

Tool/software:

Hi 

Our product use TPA2011D1, input port serial connected a 10nF capacitor and a 150kohm resistor, to test its output signal, we add a RC circuit, serial connect a 500ohm resistor, parallel connect a 10nF capacitor. Before this RC circuit, we can test square waveform, only when input standard signal range is from 3KHz/0 dB to 4KHz/0dB, after this RC circuit we can test sine waveform, if input signal at other frequency, the waveform will deeply distorted. If no signal input, we also can hear a noise from speaker. Could you help to analyze where our issue is?

  • 0
    Prodigy 10 points

     

    1.   no signal input to TPA 2011D1, test out put port after RC circuit 

    200 Hz input signal test result after RC

    2.   200Hzl input to TPA 2011D1, test out put port after RC circuit 

    1K input test result 

    3.  1KHzl input to TPA 2011D1, test out put port after RC circuit 

    1K input test result

    4.  3KHzl input to TPA 2011D1, test out put port after RC circuit 

  • 0 in reply to kai wang
    TI__Guru** 109185 points

    Hi Kai,

    Can you share a schematic or block diagram at least? It would be easier to understand how the device is connected to the different filters.

    It seems you're trying to use a square-wave (I assume PWM) as input to TPA2011D1, is that correct? In this case you'll need to add a low-pass filter at the input of the amplifier. Note that TPA2011D1 can only support analog signals up to 20kHz, so the PWM signal must be filtered so that only a signal in that range comes through.

    Best regards,
    -Ivan Salazar
    Applications Engineer

  • 0 in reply to kai wang
    Prodigy 10 points

     To test sine waveform, I remove LC filter and add RC circuit.

  • 0 in reply to kai wang
    Prodigy 10 points

     To test sine waveform, I remove LC filter and add RC circuit.

  • 0 in reply to kai wang
    TI__Guru** 109185 points

    HI Kai,

    Thanks for the additional information.
    I see now that input to the amplifier comes from a headphone output from CODEC on previous stage. That should be OK and you can disregard my comment about low-pass filter at the input of the amplifier.

    On your second diagram I see the TPA2011D1 connected to a speaker and then to RC filter, are you removing the LC filter from the first schematic for this test? Or is it still present before the speaker?
    I'd like to test without the LC filter and check if the output is OK (you can keep the RC filter for this test). The filter uses 1.5uH which may be too low inductance for a Class-D reconstruction filter.

    Best regards,
    -Ivan Salazar
    Applications Engineer

  • 0 in reply to Ivan Salazar
    Prodigy 10 points

    I have removed LC filter and keep RC Filter to test TPA2011D1 output signal, maybe because out Amplifier input signal is not a standard sine wave, TPA2011D1 also output a non-standard wave, I just want to know why its noise signal is so high from the FFT chart? The 3rd picture also shows output wave noise level is much higher than input wave noise.

    ,

  • 0 in reply to kai wang
    TI__Guru** 109185 points

    Hi Kai,

    TPA2011D1 is a Class-D amplifier, it is expected that output is a square wave without adding any filter to the measurement. The speaker connected at the output of the amplifier acts as a low-pass filter for the acoustic output, some information about this is available here: Filter-Free? Class-D Audio Amplifiers

    Is there any audible noise perceived from the speaker? The noise from the third capture may reduce if you add the signal on the other output and make a differential measurement of OUTP - OUTN.

    Best regards,
    -Ivan Salazar
    Applications Engineer