Hi,
I've designed an amp module with the TPA3255 and have built a prototype.
The TPA is in BTL mode.
During measurement the following issues were found:
- When the reset pin is pulled down, there is an audible pop on the output. (sometimes but not always a startup pop is there as well)
- When I measure on a speaker output, there is a small DC voltage (~1V measured between the pins of the speaker.)
- This voltage is also present when the speaker is disconnected.
- Both channels have this. (one is worse than the other at 1.8V for channel CD and 1V for channel AB)
- The IC gets hot when idle and will go into thermal shutdown after some time with a very audible pop.(probably because of the DC voltage)
- It is actually better to play music than to have it idle at this point
CSTART is 47nF
The strange thing is that when music is playing, everything works perfectly and when idle, the noisefloor is stable and low (as expected)
Questions:
What could cause this DC voltage on the output and how can I fix this?
What can I do to reduce the pop?