Tool/software:
Hi. We are using the TPA3255 on a different application. We made a 3 phases power supply (3 channels for current and 3 channels for voltage). Basically we synthesises a sinusoidal voltage on 50Hz or 60Hz and apply this signal to the TPA3255 board.
On the TPA3255 output, we have a transformer from 18Vrms to 240Vrms to voltage channels and 18Vrms to 15Arms to current channels.
Our TPA3255 is working on 2xBTL mode. Our PVDD is 48Vdc.
We are facing some issues exactly like described here:
and here:
TPA3255: Fault Shutdown - Audio forum - Audio - TI E2E support forums
Our product works very well, but, sometimes, when we turn the equipment on and start a synthetization, the TPA3255 stop working and sinalizes fault (sometimes FAULT, sometimes CLIP/OTW). When it happens, we need to turn the equipament off and then on again... we need to do this until it work. When it finnaly works, we can keep the equipament on for ours and ours and it do not stop again.
Reading some related questions on support forum, we find out that we could have some problems with the BST capacitors (ours is 33nF as indicated on EVM board), maby by the fact we have only 50Hz or 60Hz on TPA3255 input, and we are using a 30kohm FREQ_ADJ resistor, with gives us 450kHz of PWM frequency modulation.
As indicated by TI on the related questions, we intend to follow the application Report SLOA259. We will try a 470nF bootstrap capacitor and we would like to decrease the PWM frequency. We dind'd find any equation to help us specify the FREQ_ADJ (we look to the datasheet too) resistor value and we dont know if there is a limit to decrease it.
As we intend to apply just 50Hz or 60Hz on TPA3255 input, we are thinking on maby 300kHz on PWM frequency. What do you think about it? Could you help us?
For now, we will just put a 47k ohm resistor on FREQ_ADJ an measure the waveform to see what frequency we get.
Our board was made based on the EVM board. We have all documents (Altium schematic and layout). If necessary, we can share with you.
