• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 1627 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LM5069: Mosfet burn after connecting 48V

Pang
Expert 2415 points
Part Number: LM5069

Hi Ti,

I am designing a Surge Stopping and Reverse Voltage Protection with the LM5069 which follows the design from Ti reference link as below.

http://www.ti.com/lit/an/snva683/snva683.pdf

I had catered in my design D3 is for reverse polarity protection. During I connect my input to 48V and found that the Q1 Mosfet  will burn and the Mosfet is 80V 62A and it should be able to withstand. Please see attached schematic and advise accordingly.

  • 0
    TI__Expert 5940 points

    Hi,

    You have a 33v gate clamp, which means Vout is clamped to 33v - (Vth to Vplateau), ~ 30v.  If you sustain 48v on the input with any load for longer than a quick surge (which is what it is designed to limit), you will overheat the FET due to Vds * I-load.  WRT FET selection, please consult the design calculator tool at www.ti.com/hotswap and enter all of your system parameters including FET SOA #'s at the max Vin you operate at.

    Brian

  • 0 in reply to Brian Daugherty
    Expert 2415 points
    Hi,

    The gate clamp is 33V but I removed the Dz 33V, when I power up using 48V it will happens the same which Mosfet's Source will be shorted to Drain as well.

    There's totally no heat at the Mosfet. Can you help to advise me on this?
  • 0 in reply to Pang
    TI__Expert 5940 points
    You may have an SOA failure. SOA is heat damage at the die level that may not be enough to heat the external package.
    Use the calculator tool to determine if you have all your parameters in line.

    Brian