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TPS563209DCR heating

mandrews
Prodigy 60 points

Total power at load is 5V @ 3.244W. Allowing for 20% inefficiency all in the controller ignoring inductor and traces, input power would be 4.055W. Power loss in controller is 1.014W. With Rtheta-JA = 87.9C/W without heatsinking, Tj = Ta+89.13C. At Ta = 70C, Tj = 159.13C. Considering the metal on the board and attempts to heatsink the controller, that Tj should be acceptable.

I've had 2 controllers blow. One could have been an accidental cable short. The controller is well filtered and input and output caps are placed very close to the IC. No ringing. Vin = +15VDC and it appears clean. Still have to check for power-up spiking on Vin since the IC has a 17V limit. Spec notes says the device isn't guaranteed to operate properly above the recommended +17VDC(max) input even though abs max is +19VDC. The device has both over-current and over-temperature protection.

Am I missing something? What changes do you recommend?

Thanks,

Mike

Layout, 2-sided PCB, 2oz copper. Bottom layer is seen looking thru the Top layer.

  

  • 0
    TI__Genius 13700 points
    Hello Mike,

    Could you post a schematic and screen captures of the top and bottom of the board?
    Also could you post a screen capture of the SW node during operation? If this is an issue a snubber could be implemented if the device is experiencing over-voltage at the switch node.

    There are a few other thoughts that I have but lets start here first.
  • 0 in reply to Ryan May
    TI__Guru**** 191445 points
    Your layout is not showing...can you repost it? Waveforms and schematic as well?
  • 0 in reply to Ryan May
    Prodigy 60 points

    Hi Ryan,

    I apologize for not getting back sooner. Didn't see your email until I got a notice today someone else also commented. I'll get shots of the artwork and waveforms out in the next few days.

    Thank you for your willingness to look at this. Very much appreciated.

    Regards,

    Mike Andrews

  • 0 in reply to JohnTucker
    Prodigy 60 points
    Hi John,

    I'll get those out in the next few days. As with Ryan I appreciate your willingness to look at this. Thank you very much.

    I've reduced input and output capacitances to lower inrush as a precaution, but still within the capacitance requirements for the chip. The specs for the TPS563209DCR are very light in the thermal area. Basically it shows a layout without much explanation. I went to 2oz copper and threw on all the metal I could on a 2 layer board.

    Regards,

    Mike Andrews
  • 0 in reply to mandrews
    Prodigy 60 points

    Hi,

    Finally getting back to this. Again, thanks for your willingness to look at it. Using latest Altium, 2 layer board, 2oz copper. Here's the schematic of the regulator, and top and bottom PCB views. The waveforms are clean and appear stable. The IC does get hot. Need to measure the case temp. Per Webench IC-Top = 121C; IC-Top runs at 0.59W, all with 2A load, assuming Vin from 8VDC to 16VDC, Ta=85C.

    Original fast-proto board had just traces, no pours, with C29 = 22uF, C23 = C30 = 47uF, L=3.3uH SRR6038-3R3Y. Changed to the lower cap values shown below to reduce inrush.

    Tested all the boards to 2A even though the worst-case load should be < 1A. Two new boards have released smoke in normal operation. The others appear to work fine. It is possible we had an assembly problem, dirt on the board, ... whatever.

    Have a great weekend guys.

    Mike Andrews

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

    Still not seeing any of your uploads.  Can you try again?