Problem with TPA3122D2 amp

Discussion in 'Analog & Mixed-Signal Design' started by Phaedrus GT, Nov 26, 2018.

  1. Phaedrus GT

    Thread Starter New Member

    Nov 26, 2018
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    Hi, i recently made a copy of the TPA3122D2 class d amp by Afrotechmods on youtube and I have some problems. The output pins, 12 and 19 give 0V, and pin 6 that is supposed to give 1.54V shows 0V too. Pin 4 and 5 shows 3.5V which is not good. The speakers do not produce any sound. Can anyone help me troubleshoot?



    Here's the schematic, the polarity of the input caps should be inverted and i have done that.
    MITAXQ5.jpg
     
  2. DickCappels

    Moderator

    Aug 21, 2008
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    1,519
    It looks like a simple circuit. Did you check to see whether or not Pin 3 is grounded and pin 2 is connected to +12V?

    What are you using as a power supply, and when the circuit is connected what voltage to you see on pins 1, 10, 16, and 17? (Measure directly on the IC pins to include the effects of soldering on the measurement.)
     
  3. Phaedrus GT

    Thread Starter New Member

    Nov 26, 2018
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    I am using a breadboard to build the circuit, Pin 2 and 3 are connected correctly
    Pin 1: 12.21V
    Pin 10: 12.37V
    Pin 16: 12.22V
    Pin 17: 12.22V
    I'm using an adapter which found in my room, it outputs 12V 1A.

    Tell me if you need a photo of my circuit
     
  4. DickCappels

    Moderator

    Aug 21, 2008
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    If you can post a clear photo please do so.

    In the mean time, you might want to verify the voltages on the rest of the pins, including the grounded pins.

    If that doesn't yield insight into the problem you might want to recheck all components and connections. Sometimes (in my experience often) those plastic breadboards can become unreliable, so you might even buzz out the connections among the components.
     
  5. Phaedrus GT

    Thread Starter New Member

    Nov 26, 2018
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    Pin 1:12.21V
    Pin 2: 12.21V
    Pin 3: 0V
    Pin 4: 3.5V
    Pin 5: 3.5V
    Pin 6: 0V
    Pin 7: 0V
    Pin 8: 0V
    Pin 9: 10.6V
    Pin 10:12.37V
    Pin 11: 0V
    Pin 12: 0V
    Pin 13: 11V
    Pin 14: 12.21V
    Pin 15: 12.21V
    Pin 16 : 12.22V
    Pin 17: 12.22
    Pin 18: 12.21V
    Pin 19: 0V
    Pin 20: 0V
    I will post the photos later.
     
  6. Ylli

    Member

    Nov 13, 2015
    401
    104
    Try a low leakage cap on pin 6, even if you don't have anything as large as 1 uF, just get something low leakage on that pin and then see if it comes up to Vcc/8.

    And the gain pins, 14 and 15, should be at 2 volts for max gain. Rather than putting those on 12 volts, try a resistive divider, 2k to ground, 10k to +12 v.
     
    Last edited: Nov 27, 2018
  7. Sensacell

    Moderator

    Jun 19, 2012
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  8. Phaedrus GT

    Thread Starter New Member

    Nov 26, 2018
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    Well, i made the circuit on a PCB before, the speakers produce a ticking sound and i cant solve it. Now i made it on a breadboard and there's another problem. I will try as Ylli said, add resistors to the gain pins first.
     
  9. Phaedrus GT

    Thread Starter New Member

    Nov 26, 2018
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    Does low leakage cap mean electrolytic caps?, because i already have 1uF 25V Maxcap electrolytic cap at pin 6.
     
  10. DickCappels

    Moderator

    Aug 21, 2008
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    Film capacitors are low leaktage. I know of a low leakage Mil-spec tantilum electerlytic but have doubts about most electrolytics.
     
  11. Phaedrus GT

    Thread Starter New Member

    Nov 26, 2018
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    Pin 6 suddenly got 4.5V, I don't know why, the speakers are now able to play music with a very low level and high distortion, ears need to be close to the speakers to hear it. Pin 12 and 19 now shows 4.5V. Weird. Pin 16 and 17 shows 4V.
     
  12. rsjsouza

    Member

    Apr 21, 2014
    62
    26
    If you are measuring pins 12 and 19 with a multimeter, you should expect such voltage if the PWM is operating. However, the gain seems too little. Perhaps you could play with the gain pins and see if you are not saturating the output and making a protection circuit kick into operation?

    Also, the datasheet seems to be quite strict regarding the inductors and output impedance. Check table 3 at page 12.

    Another issue that was also pointed by others is the breadboard may be a problem in this case, especially because it is not uncommon to have flimsy contacts between the device's pins and the breadboard contacts - especially if the breadboard is well used.

    The presence of sudden voltages here and there seems to indicate this may be happening.
     
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