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LM5017EVAL/NOPB

Amita JIndal
Prodigy 80 points
Other Parts Discussed in Thread: LM5017EVAL, LM5017

I recently purchased an LM5017EVAL/NOPB evaluation board from TI's website. The board is supposed to work from 9V-100V. When I gradually increase the voltage from 0 - 74V, teh board works fine. But the board cannot handle 0-74V transient. It fails every single time when I apply 74V to the input. The LM5017 IC's pin 2 (which is Vin pin) seems to get damaged. 

Any help/recommendations would be greatly appreciated.

Thanks,

Amita

  • 0
    Prodigy 50 points

    Hi Amita,

    I'm experiencing this too.  I have ask technical for support.  If I get a reasonable solution i shall post it here.My application has the power applied and disconnected on a regular basis so this is a real show stopper if it cant be prevented.

    Paul

  • 0
    TI__Genius 11490 points

    Hi Amita,

    How do you power up the board. I suspect the input voltage at the VIN pin spikes above the rating of the part when the supply is turned on.  Do you have any scope plots of voltage at VIN pin when this happens?

    Thanks and regards,

    Vijay

  • 0 in reply to paul wilkinson
    TI__Genius 11490 points

    One way to suppress the VIN spike is to bypass the input with an electrolytic cap of appropriate voltage rating. (10uF or 22uF, >=100V

  • 0 in reply to Vijay86929
    Prodigy 50 points

    Hi Vijay,

    Thanks for that.  You would have thought the TI design engineers would have tested for this, its not as if we are applying voltage outside the specifications.  Its possible the 2.2uF ceramic is ringing with input lead inductance.  I have since seen other applications use an RC across the ceramic to help suppress any ringing and hence over voltage.

    Thanks again.

  • 0 in reply to paul wilkinson
    TI__Expert 5485 points

    Hi Paul, Amita

    Possibility of ringing due to input lead inductance can not be overlooked.  Sometimes long cable connection from Vin power source also adds to inductance. Putting electrolytic capacitors at input should help. This capacitor should be placed right at the input of your board.

    If output power level is not that high then you can add series resistor in Vin path which will form RC low pass filter and would help attenuate these transients. Typically 10 Ohm resistor should work.

    Thanks & Regards,

    Abhijeet

  • 0 in reply to Vijay86929
    Prodigy 80 points

    Hi Vijay,

    I did add 47uF electrolytic capacitor at the input. This helped with the Vin spike. I can safely turn on now up to 85V. At 85V, I am seeing the input voltage spiking to 90V still with the electrolytic capacitor. I am planning to put a pre-regulator circuit to regulate the voltage to ~85V. I did expect the chip to be more robust though so was a little disappointed.

    Thanks,

    Amita