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Issuses with LM5001 in Boost topology

Georgi Petkov
Prodigy 20 points
Other Parts Discussed in Thread: LM5001

Hi,

I've been trying to implement a simple boost converter very similar to the one shown in the LM5001 datasheet using WSON-8 package.

What I am experiencing, however, is that upon startup LM5001 gets extremely hot and goes into thermal shutdown (cycles). There is no load connected at this point. I replaced the IC thinking I may have damaged the first one but to no avail - I get the exactly same behavior.

My input voltage is 36V to 42V and output 50V @ 100mA.

What am I doing wrong?

Any help is greatly appreciated!

  • 0
    TI__Genius 12740 points

    Please investigate L9 and let us know what its saturation properties are.

    A scope shot of U14:SW would be very helpful; it should be a more/less clean square wave between 0V and Vout+Vdiode. 

    A scope shot of VCC (output) would also be helpful to see if the device is oscillating, in which case the compensation may require tuning.  Pages 9-10 of the data sheet has compensation details.

    Best, S. Dunbar, AFA Colorado

  • 0 in reply to Antenna_Head
    Prodigy 20 points

    Antennahead,

    Thanks for the reply. I did all the measurements you suggested prior to posting earlier and the results did not make any sense - VCC was pretty much 0V, SW was close to 0V with small ripple on it. That said I did find the problem - L9 (P/N SRR4028-101Y) was rotated 90 degrees effectively acting as short circuit instead of inductor. I guess people are right when they suggest to not do any work while having fever...

    All is working now.

    Thanks and cheers!

    G. Petkov