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LM5170-Q1: Converter is shorted, when turned on in short time after turn off

Erik Herceg
Prodigy 105 points
Part Number: LM5170-Q1
Other Parts Discussed in Thread: CSD18510KTT, LM5170, CSD19535KTT

Hello all,

I have 3 LM5170's in 6 phases operation in boost mode operation to step up voltage from 24V to 28V and current capability of 100A. The problem is, when I start converter for the first time, everything works fine. When I shut down the source and turn it on again in few seconds the converter is shorted to ground through Low Side transitors (it is doing the same if it is not loaded or loaded and I know it because they always burn). I thought that is caused by Crrs parasitic capacity of transitor but I was wrong and choosing transistors with lower Crrs did not helped( I have used CSD18510KTT and changed to CSD19535KTT) . When I let converter stand disconected from source for a half a of minute the converter starts successfully. I cant figure what can cause this problem. Maybe it can be caused by current loop but I tried to change values of those capacitors and resistor, but nothing helped. If I can measure something or need values of some parts which, could helped please let me know. 

Thank you in advance. 

Kind Regards,

Erik

  • 0
    TI__Guru 68495 points
    Could you show your schematic? Have you tested with our EVM?
  • 0 in reply to Youhao Xi
    Prodigy 105 points

    Hello,

    thank you for prompt answer. I have bought 2 EVMs to test current capability and I conected them in parallel. When I tested them everything worked fine, but It was few months ago. I did my revision and now I am testing it and I found this problem that was described. I hope you will be up with my schematic.DCDC_TI_28V_100A_TI4.pdf

  • 0 in reply to Erik Herceg
    TI__Guru 68495 points
    Hello Erik,

    Thank you. Your schematic does not look like a complete schematic. The same pages of the power stage are duplicated several times: having the same ref designators, same node names, which make the review and track your connections impossible. Do you also design modules, namely each LM5170 dual phase circuit is a single board, and you interconnected them to make 6 phases? Or all you 6phases are on a single board? I am afraid there is or are some unintended wrong connections in your circuit, but I can only be able to help debug with a clear, clean and accurate schematic. Please help get this schematic to me.

    Thanks,
    Youhao Xi
    System and Applications Engineering, APPBMC-BCS Product Line
  • 0 in reply to Youhao Xi
    Prodigy 105 points

    Hello Youhao,

    it is complete schematic, but I have not noticed that there are not hierarchy net labels. I forgot to chceck some options in Altium, All LM5170 are on one board, because I am limited by space in my project. So I will attach my project with those labels. I hope it will help. This is everything that I am able to export. Thank you in advance.

    Kind Regards,

    ErikDCDC_TI_28V_100A_new.pdf

  • 0 in reply to Erik Herceg
    TI__Guru 68495 points

    Hi Erik,

    Since we are communicating through private msg system, and it seems your issues reported here are resolved.  So, please click This Resolved My Issue button for our record. 


    Thanks,
    Youhao