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LM2594HV: chip failed

Zhivko
Intellectual 870 points
Part Number: LM2594HV

Dear support,

i was using LM2594HVM-3.3/NOPB in this configuration. It worked OK when supply was 24V, but it failed with burning smoke with supply on 48V.

I use it to power STM32F3 that runs on 3.3V.

Full schematic and gerbers attached.

Do you see some mistake why this would not work on 48V DC? 

Since VIN leg was smoked blown away could it be that bigger cap is needed nea VIN leg?

What would be the problem. I attach schemeatic and photo of board.

Gerbers.zip

  • 0
    TI__Guru 64385 points

    Sounds like an overvoltage spike.

    Be sure that your input supply does not overshoot; try to measure the input voltage with a 'scope

    when performing the test.

    Is this a "hot plug" type of test?

    Be sure that the diode is rated for you input voltage.

    What is the value and current rating of the inductor.

    Can you send a snapshot of your top layer and ground layers.

  • 0 in reply to Frank De Stasi
    Intellectual 870 points

    "hot plug" meaning what? I just plugged the jack of 48V, 3A to the jack socket on pcb.

    You can see big capacitor ( VISHAY  MAL225099913E3  SMD Aluminium Electrolytic Capacitor, Radial Can - SMD, 470 µF, 100 V, 250 CRZ-V Series) on top near the power jack.

    there is aprox 10cm long trace of 48 that goes to VIN of LM2594HV.

    Diode is:

    VISHAY  VS-MBRS1100-M3/5BT  Schottky Rectifier, 100 V, 1 A, Single, DO-214AA, 2 Pins, 780 mV

    Inductor is:

    BOURNS  SRR4828A-221M  Power Inductor (SMD), 220 µH, 500 mA, 240 mA, SRR4828A Series, 4.8mm x 4.8mm x 2.8mm, Shielded

    This is second time this happened (burned chip) uC ST32f3 has been also fried (could you suggest what to do to protect microprocesor for next time? Can I add some voltage limiter or some diode? i need voltage nt to go aabove 3.3V that is supply for st32f3).

    top copper:

    bottom:

  • 0 in reply to Zhivko
    Intellectual 870 points
    Maybe I need some additional parts TVS diodes maybe? If yes which ones? On both power lines - for 48V and 3.3V? Could you suggest parts if possible please?
  • 0 in reply to Zhivko
    TI__Guru 64385 points

    Yes, hot plug means plug it in with power.

    Sometimes this can cause a ringing transient from the inductance and capacitance of the input system.

    You have a 22uF Al. on the input; that should be OK.  You can increase this to 47uF to 100uF; that may help.

    Your layout seems OK.  I would try to get the grounds of the diode/Cin/Cout closer if possible.

    Yes, you can use a TVS on the input and output.  I would size for something between your maximum input voltage and the Abs max of the device.

    For the output you would size for the maximum that the load can tolerate.