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TPS54060DGQ smokes

Sophi
Prodigy 120 points
Other Parts Discussed in Thread: TPS54060, TPS54040

Hello!

I have an issue with TPS54060DGQ. I'm using component values from the SwitcherPro designer. I didn't use the exact suggested diode but similar.

I followed the layout suggestions.

I am hand soldering with an iron. I have one board which seems to be working but I have had 4 boards fail and the part that fails is the TOS54060. It just gets really hot and smokes.

There is good continuity from PowerPad to GND pin. There is only one large via in the PowerPad to the GND plane and one large via just to the top of the PowerPad to the GND plane.

Any thoughts?

Thanks!

Sophi

 

 

 

 

  • 0
    TI__Guru**** 191445 points

    It is important to ensure that there is adequate soder on teh powerpad to pcb connection.  I doubt that you can accomplish that with hand solder.  The other thing to consider is shorts on the board.  At no load, the TPS54060 should not get too hot, even with a poor powerpad connection.  Can you telll us a little more about your operating conditions?

  • 0 in reply to JohnTucker
    Prodigy 120 points

    Thanks John.

    I do not have any load at all connected to the Power supply output. It is a new PCB and I tested it for shorts before soldering on parts.

    Although I agree that the hand soldering could be causing our problem, The PowerPad appears to have a solid connection as I cannot easily un-solder it.

    The SwitcherPro was designed for the 54040, and then due to parts shortages, I am using 54060 with the same (SwitcherPro for 54040) design. Let me know if I can send you the SP designs.

    When I run the SwitcherPro on the 54060, it is very similar.

    I just soldered a new board, with a higher value inductor. At first start up, I get 3.3V at the output for about 2 seconds. Now the chip is not getting hot, but I get the same voltage on the output (14V) as on the input (14V) so the chip is not working.

    I usually get this symptom just before it gets hot and blows up....I just thought this time I would stop early.

    Thoughts?

    Thanks!

  • 0 in reply to Sophi
    TI__Guru**** 191445 points

    The TPS54040 and TPS54060 are mostly compatible except for the input voltage range.  With 14 V input there should not be a problem.  If the ouput is the same as the input and the device is not switching it is very likely that the internal FET has shorted.  If you are using the online switcherpro you can send me the design from the notes page.  I can take a quick look at it.

  • 0 in reply to JohnTucker
    Prodigy 120 points

    OK here is the design that I am using.

    Why would the internal FET be shorting? I have burnt out 5 chips.

    power supply schematic.pdf
  • 0 in reply to Sophi
    TI__Guru**** 191445 points

    I don't see anything in that design that jumps out at me.  The compensation may be a little agressive at very low input voltages, but at Vin = 14 V, there is plenty of margin.  Can I inquire about your level of expertise regarding dc/dc converters?  Are you sure that all of the capacitors and inductors are rated properly?  It may help to see your layout as well.  The next step would be to bring the supply up slowly and observe the swithing node etc.  can you sipply any waveforms?

     

     

  • 0 in reply to JohnTucker
    Prodigy 120 points

    Hi John, thanks for the reply.

    Can you explain what you mean by the following sentence? I have often started at a lower than 14V and brought the voltage slowly up.

    The compensation may be a little agressive at very low input voltages, but at Vin = 14 V, there is plenty of margin. 

    Can I inquire about your level of expertise regarding dc/dc converters? Total NOOB.

    Are you sure that all of the capacitors and inductors are rated properly? I think so. I used the BOM that came with the SwitcherPro design and where I used anything different, I used similarly rated parts.

    It may help to see your layout as well.

    OK, can I have your email address?

    The next step would be to bring the supply up slowly and observe the swithing node etc.  can you sipply any waveforms?

    I put a current sensor on the output of the chip (between pin 10 and inductor). No waves at all.

    Thanks for your help!

  • 0 in reply to Sophi
    Prodigy 120 points

    Update: all parts check out OK rating-wise. The differences in the SP circuit and my circuit:  I am using a 33uF cap at C9 - the cap from Vin to gnd (SP says 4.7uF),  no C1, an additional capacitor (33uF) from the enable pin to ground, and C2 Vout to gnd is also 33uF instead of the recommended 22uF.

    Thanks!