TPA3251: Power Up Error

Hi,

Could you check if there is any short across the PVDD/OUTx/GND? There is a PPSC function to detect any short across these pins, if there is any short, then the fault pin will keep in low. You may refer to datasheet for more detail.

Thanks!

Regards,

Sam

Hi Sam

Sorry, I should have said I checked for shorts and there are none there.

Rich

Hi Rich,

The behavior you described is so similar to the PPSC behavior... Could you please measure the diode voltage on the GND->OUTx, and OUTx->PVDD? Probably it's not a directly short, but some low resistance connection.

Also, could you use a oscilloscope to probe the OUTx pin, and see if there is any periodical signals on that? Thanks!

Regards,

Sam

Hi Sam

Yes, it does look like PPSC behaviour.

diode check PVDD>OUTx is 0.4V, OUTx>PVDD 0.4V

There is no direct short between GND>OUTx, measures around 150K which is similar to a working board. Likewise with OUTx>PVDD, around 150K

no sign of switching on outputs

Rich

Hi Rich,

Recently I just got a very similar issue with you. When I power it up, the fault light on EVM lit up and there was no switching.

I checked the body diode voltage across the PVDD/OUTx/GND. It turns out to be a soldering issue as I noticed the forward voltage drop of one of these diodes is much different with others. After I take the device down and soldered it again, the issue disappeared.

Hopefully this can help on your debugging. Thanks!

Regards,

Sam 

Hi Sam

That makes sense, unfortunately I already tried re-soldering it and it made no difference.

I'm missing something, but can't see what!  I even checked all the output caps for damage etc.  I think I'll have to use a good board to swap bits out with

Rich

Hi,

Yes, you may try the A-B-A test and find out the issue is following the device or the board...

Thanks!

Regards,

Sam