TPA3255: TPA 3255 shutdown after 3 seconds playing

Hi Louie,

Can you give us more details of your system?

- impedance of the load/speaker

- I tried looking at what type of inductor you are using but it was in chinese. Do you have the datasheet for it? 

Regards,

Robert Clifton

Impendence of load is 8ohm, a 6.5 inch subwoofer.

Below is the inpendence I use. 6R8M.

I do not use the standardized startup capacitor and replace1uf with 3.3uf, I do not know whether it really matters.

Thanks!

Hi Louie,

So does the device shutdown whether you are playing audio or not? If you turn the volume down do you see the same shutdown? 

Another thing I don't see is the inductance curve vs current for the inductor. If the inductance drops below 5uH then the amplifier can shutdown since the minimum expected impedance is violated. 

Regards,

Robert Clifton

Robert,

Thank you! I'll do these tests later to see if it still goes into a fault mode in those circumstances.

Another problem I met is TPA3250 shutdown. Two sample boards meet the problem that when I press the chip, it works but when I stop pressing it it goes into a fault mode,

I suspect it is because manufacturer use high temperature and injures the chip but not sure. I am now trying to reassemble boards to check it. If there is any useful information, appreciate if you share with me.

Regards,

Louie LI

Hi Louie,

So you are also using a TPA3250? 

This sounds like there wasn't a good connection between the thermal pad and the PCB since this is a pad down device. This does sound like a thermal issue from your description. Under what conditions are you testing the device under? 

Regards,

Robert Clifton

Hello Robert,

I am very thankful for your patient in helping me! Now I have a good news to tell you:

I find where the problem with TPA3250 and TPA3255. In another early version the problem does not happen because I connect /RESET and DVDD with a 100k resistance. In this two new evaluate board of 3250 and 3255, I leave /Fault pin float because I thought /RESET pin is internally pulled up.

I want a double check if a pull-up is compulsory and what are possible sollutions to make / RESET work stable.

I reviewed function of  /RESET again and see that connecting it with DVDD is totally OK.

Another new question is: Can I connect /Reset pin with /FAULT or /OTW Pin directly to realize an auto-reset function when fault or overtemperature happens?\

Thank you!