Blown TPS54386, Why?

Daniel Zangrilli

Other Parts Discussed in Thread: TPS54386

I created a PCB using the TPS54386 chip. I designed my circuit using the Switcher Pro application as a resource. In my circuit, Vin is 24V and the outputs are 12V and 5V. I powered the circuit at first without a load connected. When doing this, the voltages were correct. Next I tried to power a Beaglebone using the 5V output. When attempting this the TPS54386 caught on fire. When examining the damaged IC, it looks as though the damage occurred around the Analog Ground, EN1 and EN2 pins on the chip. Any suggestions?

As a side note, when removing the chip, it may have been possible that the PowerPad was making contact but not soldered fully to the ground trace/plane. Could this have caused an issue? The Beaglebone is still functional.

over 11 years ago

0 JohnTucker over 11 years ago

TI__Guru**** 191445 points

The TPS54386 thermal pad should be well soldered to the exposed copper under the ic. For that type of destructive failure, usually over voltage is the cause. I am not familiar with a "Beaglebone". Did you hot plug it to the 5 V output while the TPS54386 was powered on? I would recommend getting your board up and running then add resistive load up to the rated output current before attaching any actual load circuits if you are having problems. I suppose it is possible it may be layout related though. Can you post your schematic, PCB layout?

0 JohnTucker over 11 years ago in reply to JohnTucker

TI__Guru**** 191445 points

Looks like a beagle board needs only 1 A. TPS54386 should be able to provide that.

0 Daniel Zangrilli over 11 years ago in reply to JohnTucker

Prodigy 40 points

Here is an image of my schematic and pcb layout. And I didn't hot plug the power into the Beaglebone.

5661.TPS54386 Schematic.pdf

2744.TPS54386 PCB.pdf

0 Daniel Zangrilli over 11 years ago in reply to Daniel Zangrilli

Prodigy 40 points

John,

Any chance to take a look at my schematic/pcb to verify it looks correct?

Thanks

0 JohnTucker over 11 years ago in reply to Daniel Zangrilli

TI__Guru**** 191445 points

If you post it I will take a look.

0 Daniel Zangrilli over 11 years ago in reply to JohnTucker

Prodigy 40 points

John,

I attached both pdf's a couple posts above.

0 Alireza Sadri over 10 years ago in reply to Daniel Zangrilli

Prodigy 20 points

Hi,

I am having the same problem, explained here:

http://e2e.ti.com/support/power_management/non-isolated_dcdc/f/196/t/307914.aspx

I have attached pcb and schematic there ....same thing.

Any comment?

thanks

0 JohnTucker over 10 years ago in reply to Daniel Zangrilli

TI__Guru**** 191445 points

Your schematic seems ok. Do you know the ESR of your output capacitors? I assume you followed the datasheet recommendations. The layout is pretty much a problem. To start with it looks like your input capacitors, C1 and C2 are electrolytics, they should be ceramic types and placed as close to the IC PVDD pins as possible. You have used a poit to point connection scheme similar to what you might find for digital connections. Dc/Dc converters require strict layout procedures. For example your SW1 trace winds out from pin 4 and connects to C3, then D6, C9 and L3. In general, that should be a short wide trace. The idea is to make the circulating loop from pin4 to D6, L3, thru C8 and back to the IC ground as short as possible using suitably wide etch or copper fill areas. I suggest you take a look at the TPS54386 EVM users guide as an example of a layout that is known to work well:

http://www.ti.com/lit/ug/sluu285c/sluu285c.pdf

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Blown TPS54386, Why?