We have the same problem with TPA3116D2. The amplifiers repeatedly go into protection (trip) with FAULTZ going low when certain audio tracks or sine waves of certain frequencies are being played.
First, we found this problem in our amplifier, and then went back to the evaluation kit. It was very easy to reproduce the problem on the evaluation kit.
The test setup is as follows:
TPA3116D2EVM 6525164 RevC evaluation kit;
A fan for the amp IC heatsink;
12-15V 15A power supply;
2 Ohm resistive loads x2;
Audio source (PC);
Oscilloscope.
Evaluation kit configuration: all jumpers are on except JP5 and JP6.
Oscilloscope is set to monitor 3 signals: input (blue trace), output (yellow) and FAULTZ (green). The FAULTZ signal was used to trigger the scope to see what happens when the amplifier is going into protection. The amplifier output being monitored is Right+ in relation to the ground.
Two screenshots are provided for two types of modulation: with JP7 On on the left and JP7 Off on the right.
The input here is a 15 kHz 2.5VP-P continuous sine wave. The supply voltage is stable 14.4V. The heatsink is cold to the touch. It's fastened securely.
The amplifier trips and restarts approximately every second.
We have found that the amplifier trips when high input frequencies (12-19 kHz) are being used. The higher the volume, the more is the probability of the fault.
The following screenshot shows how the amplifier trips with music instead of the sine wave. Apparently, the high frequency content causes the amplifier to trip:
Previously, we also observed the fault using 4 Ohm resistive loads, 4 Ohm speaker loads and no loads.
We have found that increasing the value of the capacitors C21, C22, C23, C24 increase the probability of the fault occurring. The stock value is 0.68uF, which is currently being used. We also tried up to 2.2uF to reduce conducted emissions which we had a problem with originally.
We suspected that the LC circuits L1+C21, L2+C22 etc. oscillate at their respective LC frequencies, and this is the cause of the failure. However, there is not enough evidence to support this hypothesis.
We can reproduce the problem from -5 deg C to +55 deg C. When using music, the higher the temperature, the less is the probability of the fault occurring.
This problem will have a direct impact on the user: as they increase the volume, the amplifier will start to cut out. This is a major issue for us. Does anyone know what is the root cause and how to deal with this?
