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.

TPA3122D2 verbatim board will not work

I built a board based on the TPA3122 diagram in the datasheet. It did not work, so I built another with exactly per the drawings, and also those from a kit (jerryselectrionics.com). It too does not work. Maybe someone can see an error if you have time to look at it. 

Red Positive, Green Ground, Blue Right input, Yellow Left input, White + Output, Black - Output. 

When I give this 24VDC  (+24,0) and a 60Hz 1.5V wave input, I hear nothing except some rythmic popping, about every 1 second. The scope shows no wave, but a little burst of noise each second.

I have the SD pin high, and Mute pin low. I have looked very closely for solder traces between pads.

Any comments would be appreciated.

Curt

(209) 483-3910

  • Hi, Curt,

    From your description, it sounds like you are tripping the short-circuit protection. This can be due to either too small of a load, or excess capacitance on the outputs. What is your cap to ground on the output inductors?

    -d2

  • You may be right. It could be over-amping, and then shuts down for a second and tries it again.

    My cap to ground on the output is 0.68uF per the diagram. My load is a 28W 4Ohm speaker.

  • I just hooked up only an 8 ohm resistor across the outputs and it still does not work..

  • I found a possible answer in another post related to the TPA31xx family:

    Hey! I know this is an old thread, but I had the same problem and just figured it out. 
    Promlem's hiding in Mute and Shutdown features. You shouldn't connect mute/shutdown pins directly to VCC/GND rails, connect them via an RC low-pass filter and everything will be fine. 
    I think that it should be be mentioned in next datasheet revision, not an obvious issue as for me.

    If a low pass filter is to be built,  I would very much appreciate a diagram from TI, or at least some values since my application is very reliability sensitive.

  • I have confirmed that it is the shutdown pin (Pin 2) that is causing this. I lifted the path from the board and jumpered the shutdown pin to Vcc a couple times and it started working. I have done this a few times, and it is not reliable. Sometimes it starts, and others I need to play with it.

    I would really appreciate a solid solution to this. Maybe an updated diagram. 

     

  • Hi, Curt,

    Sometimes leakage on the BYPASS capacitor can cause start-up problems. Make sure there is no flux or other leakage path on the capacitor. If it does not charge up to the full value, the part won't start up.

    -d2